Torque Arm vs 4-Link

[AEH]

I have a question regarding which suspension type is best for me and how I plan to use my car. I have searched this forum and every other resource I can find, read every article I can find but still have found no definitive answer to my question. IF there is, please post a link. I've think I've read everything David Pozzi has made regarding suspensions and have not ever seen it addressed from my perspective. Every discussion I read is coming at it from the "what suspension performs best" perspective, and there is not really even a consensus there either. First a little background.

I have a 69 Camaro I am getting ready to start building. My buddy had the car for the last 15 years sitting in his barn and finally agreed to let me have it. He had already replaced all the rot so it's a good solid body to start with.
I bought a Crate LSA and don't plan (at this time) to go much over stock. I'll make a few tweaks, Maybe 650hp at the motor, but pretty tame on a relative scale. I have a New Vintage Racing sub-frame fully dressed with all new parts, Ridetech Adjustable shocks, Z06 big brakes, etc. I picked it up from a friend, $4000 was where I couldn't say no. (so there goes the Stick with one vendor front & rear argument) I may not use the big brakes if I decide on 17" wheels (for more sidewall) but right now that's what on it. The Ridetech's have 500lb springs and I'll probably reduce the rate for a smoother ride too.

I'm not exactly sure how to put this so this thread wont take a tangent, but here goes. My intent for the car is to build a very nice cruiser we can drive anywhere we want to go and still enjoy the ride. I don't want to be cussing it after 8 hours or have to argue with the wife whether or not we take the Camaro on the next trip. I realize everything is a compromise but I want all the performance I can get without sacrificing ride. I will never track the car and it'll never see the drag strip. I want it to be fast and capable and there will be times I'll push it, but I'm not trying to win any titles or even compete. It's just gonna be My Car. I'll get the best seats I can find, use all the sound dampening and Insulation I can get in it and probably soften whatever suspension I end up with.

So now my question. Which is better suited to meet my needs, Torque Arm or 4 Link. Again, a Smooth, Quite and comfortable ride is my top priority, but I want all the performance I can get with that in mind. I think I know whose 4-link and whose torque arm I like best, so I'm not trying to pick a vendor, I'm just trying to figure out which Geometry/technology is better for me. Either would certainly meet my performance objectives. I do realize I just made a pretty good argument for Leaf springs, but there is not any wow factor in that. No Offense to the guys running mono leafs, that's just not what I'm shooting for.

Let me try and stave off one of the typical expected comments. I realize a 69 Camaro will never be a 2020 Cadillac or a BMW. However, I do think we can improve on both ride and performance and If I wanted a Cadillac, I'd get one. Frankly it would be a whole lot cheaper, lol.

I know this was a little long winded, but I would appreciate any input and I hope I didn't come across as anything other than sincere. Mike

[Pragmatist]

There are good reasons GM went with a torque arm. That being said it's more about finding the right spring and shock combination to reach your goals.

[dhutton]

Regardless of which you choose try to steer clear of metal on metal heim joints. They negatively impact ride quality imho. Also pay attention to sway bar rates. Generally soft spring stiff bar cars ride better. Cheap poly bushings wear quickly in my experience.

I think all of these systems ride harsh because lowered cars generally require stiffer springs to limit suspension travel. None of them seem to incorporate any sort of progressive rate bump stops. They are simple designs to keep costs competitive.

I’ll also add that my Art Morrison IRS equipped 69 Camaro is the nicest riding first gen F body by far in my experience. There is a reason why the OEMs have migrated from four links and torque arms to IRS....

Don

[AEH]

Thanks for the input. I realize shock valving and spring rates are a big part of the equation for any suspension and I’m willing to spend the time to tune it. The only 4-links I’ve been around we’re straight line cars and they were harsh and loud. I’m sure the heims were a big part of that and I know most are going with a bushing type Jonny joint now which I’m sure helps the noise. Good info on the stiff sway bar. That’s a little counter intuitive to me. I would have guessed the opposite. I’m not sure what the rate is on the bar that came with my subframe but I was worried it would be too stiff.

I’d love to go the IRS route but that’s a bit out of reach.

[Vimes]

Between the two options you selected, for the sort of performance you're looking for, I'd go with the torque arm. It packages better, it makes for a more stable, comfortable driver in case the 'ol lady needs to drive, and it does well on both acceleration and braking. And, lucky you, there are several companies that make complete torque arm kits for your car. 4-links are more of a drag strip rear and their main purpose is weight transfer in a straight line. I would suggest a 3-link, but everything I've seen on them requires mounting the top link where your back seats are.

[BMR Sales]

Our Torque Arm Kit is complete Bolt-On system.

4 Links are usually going to take some fabrication

https://i.hmjimg.com/images/2018/09/28/_MG_2959.jpg

[stab6902]

For a smooth quiet ride, rubber bushings are the way to go. They take the edge off initial impact harshness and reduce NVH. There's a reason why 99.9% of modern cars use rubber bushings - not poly or delrin, and especially not heim joints. The type of bushings will have more of an impact on ride comfort than whether it's a 4-link vs torque arm. As I've said before, as long as the kinematic properties are the same (instant center, roll center, etc), the number of links doesn't really matter. You want whatever packages nicely and has the minimum amount of unsprung weight.

Off the top of my head, I think DSE is the only company that offers a rubber-bushed aftermarket rear suspension setup for first gen F-bodies. That'd be my pick if I were in your shoes.

[BMR Sales]

For quietness, Rubber Bushings do a good job, but they also bind.

For performance, Poly does a Great Job

For Racing, Rod Ends, and Bearings are the way to go

[stab6902]

The DSE control arms have the "swivel link" to address any binding concerns during twist.

[AEH]

Thanks all for your input. I was hoping there would be a more of a consensus, something definitive to make my decision easier. I don’t plan to lower the car as much as most. As mentioned it takes some room for a suspension to work, and more importantly, I’m Just not a big fan of real low first gens. Don’t get me wrong, some of the cars look badass, it’s just not what I’m shooting for. I know that shows my age but I just prefer the look of closer to stock ride height. I also think the more sidewall the better for ride quality. So I guess I’m kind of an oddball, and I’m trying to get the performance without as much of the look.

It’s all way more complicated than it first seems. There are a lot of variables and I don’t really understand how they all interact. It would be a lot safer to follow a recipe of tried and true combinations but I’m trying to figure out what I need to do to end up where I want to be without wasting a bunch of time and money.

Don, do you have a build thread showing how you fit the 6L90 in the 69? I’d like to see how you packaged it.

[Vimes]

The nice thing about a torque arm, you can go test drive any 4th gen Camaro/Firebird to get an idea how you'd like it.

You can also hit the net, asking XXX vs XXX suspension questions. Some of the sites are going to be low tech ricer sites, most are going to be "buy my product" sites, but there are some tech-rich sites out there. Quite a few of the hits will come from this very forum.

[dhutton]

Don, do you have a build thread showing how you fit the 6L90 in the 69? I’d like to see how you packaged it.

Sorry I don’t have a build thread but because I have an IRS not much applies. With an IRS the pinion doesn’t move which allowed me to push the transmission and driveshaft high into the tunnel to get good ground clearance for the transmission pan.

Don

[Sleeper68]

Every discussion I read is coming at it from the "what suspension performs best" perspective, and there is not really even a consensus there either.

That's the million dollar question.


The Ridetech's have 500lb springs and I'll probably reduce the rate for a smoother ride too.

500lb/in is actually kind of soft depending on your motion ratio. Since you have a factory subframe I assume you are using the factory motion ratio. I run 600lb/in front springs in my factory subframe. My camaro rides better than my bone stock 2019 Subaru WRX. 500lb/in could work but really it depends on the weight of the car on the front tires. Shocks (dampers) are also very important in regard to ride comfort.


My intent for the car is to build a very nice cruiser we can drive anywhere we want to go and still enjoy the ride. I don't want to be cussing it after 8 hours or have to argue with the wife whether or not we take the Camaro on the next trip. I realize everything is a compromise but I want all the performance I can get without sacrificing ride.

Seems relatively easy to achieve.


I will never track the car and it'll never see the drag strip. I want it to be fast and capable and there will be times I'll push it, but I'm not trying to win any titles or even compete.

The obvious solution is leaf springs.


It's just gonna be My Car. I'll get the best seats I can find, use all the sound dampening and Insulation I can get in it and probably soften whatever suspension I end up with.

This will definitely help with ride quality and comfort.


So now my question. Which is better suited to meet my needs, Torque Arm or 4 Link. Again, a Smooth, Quite and comfortable ride is my top priority, but I want all the performance I can get with that in mind.

Neither, leaf springs. You have no use for a 4 link, 3 link, or torque arm. If ride quality is paramount, the lightest system (least unsprung mass) is best so the suspension can react to bumps. 3 links (NOT torque arm) are usually the lightest of the link systems. 3 link vs leaf springs are comparable in regard to weight. Leaf springs are immensely less expensive.


I do realize I just made a pretty good argument for Leaf springs, but there is not any wow factor in that. No Offense to the guys running mono leafs, that's just not what I'm shooting for.

Very few people I know run mono leaf springs unless they have an unrestored car. My leaf springs are 5 ply. They work great. If "Wow factor" is a stipulation, you need to put that in your list of requirements in the beginning. If you are intolerant to leaf springs then I suggest a 3 link with a Watts Link centering device (not a panhard bar). A panhard bar will feel worse on on-ramps over bumps.

[Mark@lateral-dynamics]

Lot of good info on this thread, but also some not so good.

Ride quality is very dependent upon a number of things, suspension design (links, leafs, T/A - meaning both Truck Arm and Torque Arms) "may" be a big part of it. And maybe not. Spring rates, damping rates, bushing choice (rod ends, rubber, delrin, etc) also play into things. Or not. Here's "our" run down, with full disclosure that we are a supplier to this hobby.

Aside from supplier choice, and assuming that the quality of the design and manufacture is good enough, all Torque Arm systems on the market are essentially the same. They are a good option for a bolt on solution, or "nearly" bolt on, and anyone that owns one, or all of the suppliers of them, will tell you they are the best solution ever invented. They all have the same advantages, and the same downfalls. The shorter the actual "arm" in the system, the worse. Packaging a suitably long Torque Arm greatly interferes with the almost required "x" pipe in the exhaust. They all suffer from potential (which translates to "will have" if you push the car hard enough) brake hop issues.

Aside, again, from supplier choice, with same assumptions, all Triangulated 4-Link systems are essentially the same. They package very well, but the overall geometry (purely from a performance and engineering standpoint) leaves very much to be desired. Anyone that owns them, and all of the suppliers that produce them will tell you they are the best solution ever invented.

Truck arm setups, though not mentioned here, have essentially the same performance disadvantages as Torque Arms. Watch NASCAR. At Sear's Point (Sonoma Raceway) and see how many times the commentators speak of wheel hop in the really hot braking zones. Maybe not an issue for a purely street driven car, but it's a fact. And they break axles ALL the time as a result. Anyone that owns them, and all of the suppliers (which are few), well, you get it.

"Four link" systems, with the addition of a Panhard Bar or Watt's link, aren't "4 links." They are 5 links. And this means that they are mechanically over-constrained. Which is why they handle like crap, they fundamentally bind in roll. Ask any capable Mechanical Engineer. They will ONLY work if you use rubber bushings, which most do, which masks the binding aspect. Anyone that owns one........

Three Link systems, with the addition of either a Panhard Bar, or a Watt's Link to manage the lateral loads, do not suffer from ANY of the above disadvantages with all of the other stick axle setups, if designed and engineered appropriately. A 3-Link is NOT the same as a Torque Arm, the mechanics are completely different. The downside is typically packaging. In our "Next Generation" 3-Link systems, we strove to minimize this aspect, while preserving (and in many aspects, "improving") the performance attributes of our legacy systems. The ones who scored the inaugural Optima Ultimate Street Car honors for "Bad Penny," class wins at the One Lap of America, Targa Newfoundland, and many other events that our customers compete in. 3000+ mile long bucket list road trips? Check. Wow factor? Check. So, yeah, we as a supplier will tell you they are the best invention solution currently available. Ask any question, and we will tell you WHY we did what we did. We have a re-introduction thread on the suspension page of this forum, check it out.

Most of all, have fun, whatever path you choose will be a good one. Enjoy the hobby, and be well.

[stab6902]

"Four link" systems, with the addition of a Panhard Bar or Watt's link, aren't "4 links." They are 5 links. And this means that they are mechanically over-constrained. Which is why they handle like crap, they fundamentally bind in roll. Ask any capable Mechanical Engineer. They will ONLY work if you use rubber bushings, which most do, which masks the binding aspect. Anyone that owns one........


I respectfully disagree with a couple of things mentioned here, but the biggest one is the knock on parallel 4-links. I know of several cars running them that don't handle like crap. You be the judge regarding whether the builders/owners are capable mechanical engineers or not.

https://www.hotrod.com/articles/mark-stielow-built-12-camaros-so-you-dont-have-to/

https://static1.pt-content.com/images/pt/2020/10/888a621b5e4f95d575eab008db6bb0c6-1.jpg

[chevelletiger]

Well,dse does use moog k5144 rubber(mexico) bushings,thats why there system doesnt bind,and the swivel link which and no offense to them or anyone using there parts it's more of marketing idea,a shaft with a bronze bushing,pretty heavy too.
Just my opinion since I looked at there patent drawings.

And let's be honest here now tucker,stielow were/are GM engineers ,that have WAY more track time,


FEATURED, MUSCLE CARS, NEWS

1969 CAMARO LT5 CURRENTLY IN THE WORKS BY MARK STIELOWIt Will Incorporate A C7 Corvette ZR1 Crate Motor That Could Have Upwards Of 900 Horsepower

by Manoli KatakisApril 24, 2020, 6:46 pm

General Motors has a battalion of performance drivers that have achieved amazing lap times on tracks like Virginia International Raceway and the mighty Nürburgring. One of them of particular note can be only described as a Yoda equivalent of the group. The Jedi Master that oversees the rest of the group. This person is Mark Stielow, and he has also made a name for himself outside of GM’s Milford Proving Grounds. He’s also the godfather of the pro touring movement – particularly when it comes to the Chevrolet Camaro.

So.....they have more racing experience then the competition they had run against...lots more.

[Sleeper68]

Lot of good info on this thread, but also some not so good.
"Four link" systems, with the addition of a Panhard Bar or Watt's link, aren't "4 links." They are 5 links.

Using that logic, your "3 link" is actually a "4 link."


And this means that they are mechanically over-constrained. Which is why they handle like crap, they fundamentally bind in roll. Ask any capable Mechanical Engineer. They will ONLY work if you use rubber bushings, which most do, which masks the binding aspect. Anyone that owns one........

This is specific ONLY to triangulated or trapezoidal 4 link systems which don't use separate centering devices.

Parallel 4 link systems require separate centering devices and don't bind as easily. they are comparable to 3 links in terms of available travel. Both are very capable systems.

All solid axle systems bind in roll, it is just a matter of how much travel is available before binding occurs.


I respectfully disagree with a couple of things mentioned here, but the biggest one is the knock on parallel 4-links. I know of several cars running them that don't handle like crap. You be the judge regarding whether the builders/owners are capable mechanical engineers or not.

Exactly. Mark and Kyle are very well versed in vehicle dynamics and are fantastic drivers.

[Pragmatist]

Lot of good info on this thread, but also some not so good.

Truck arm setups, though not mentioned here, have essentially the same performance disadvantages as Torque Arms. Watch NASCAR. At Sear's Point (Sonoma Raceway) and see how many times the commentators speak of wheel hop in the really hot braking zones. Maybe not an issue for a purely street driven car, but it's a fact. And they break axles ALL the time as a result. Anyone that owns them, and all of the suppliers (which are few), well, you get it.
Most of all, have fun, whatever path you choose will be a good one. Enjoy the hobby, and be well.

I guess it depends on how the truck arm is designed. NASCAR requires truck arms of 38lbs. each. I built composite arms of 12.5lbs. each. Due to their ability to flex I have yet to see brake hop at a track day and I would challenge anyone to build a lighter rear with a live axle.

https://www.youtube.com/watch?v=San17XlQCGM

[Pragmatist]

All solid axle systems bind in roll, it is just a matter of how much travel is available before binding occurs.

Unless the link itself flexes.....

[dontlifttoshift]

Using that logic, your "3 link" is actually a "4 link."
.

Actually, with a watts, it's a 5 link. :head assplodes:

I will take a perfect version of any of the suspensions over a compromised version of any of the others. I have personally owned vehicles with leaf springs, truck arms, triangulated 4 links - with the upper bars in both directions, and 3 links with PHBs.

The best rear suspension was the one that packaged the best in that vehicle and fit my needs for budget and time commitment to install.

If I were the OP, the only rear suspension I would be considering would be the DSE QuadaLink.

[stab6902]

If I were the OP, the only rear suspension I would be considering would be the DSE QuadaLink.

To the OP, I think this is about the closest you'll get to a consensus - so far two of us, with nothing to sell you, are recommending the DSE QuadraLink.

[Mark@lateral-dynamics]

Using that logic, your "3 link" is actually a "4 link."

This is technically correct.

For the record, I have NOTHING against DSE, Kyle, or Mark. I have met both of them and we have always been cordial, have had some excellent technical communications with Mark in particular though it was many years ago. Kyle has built an empire, and I am happy for he and his team, they really created a lot of opportunity for others, such as our operation, because the hobby has grown so fast and so large. They make exceptional quality products, and we use a lot of their stuff on our own cars (just not suspension). Likewise, I have nothing against anyone's opinion, but I am a technologist and don't pull punches when challenging opinions that are in direct conflict with fact. Can't help it, it is just how I am wired.

There are two very prominent 69 Camaro's in So Cal that regularly compete in the various auto-x and USCA events. Both of them started out with Parallel 4 Link - with PHB rear suspensions (rubber bushings). Years of experience running those setups. Both of them, within the last few years went with completely different setups, and both of them got a lot faster. One of them won the whole enchilada at the Optima event. The other took second place at a highly touted invitational shootout, second only to a brutally fast mega build. These are facts. Now, not everyone competes at this level, and that is completely fine, and again, pretty much any aftermarket system will be a huge improvement over any factory style setup. And, as one can see, there is present even here, significant brand loyalty. I am merely trying to promote our brand, is that so bad?

Be well.

[dhutton]

I think the truth is that most folks are unable to out drive their car, at least I am. That being said I love these tech discussions.

Don

[dontlifttoshift]

Promote away. The flip side of that is you have to support your assertation..... or facts.

Read the OP and tell me what your 3 link does better than the Quadralink for that application.

For the record, I like you and your product and I believe this place and the hobby/industry is better with you in it. Your posts were some that I paid attention to when I started here.

I am partial to DSE parts but my parts selections and recommendations are still very application/end user specific.

[dontlifttoshift]

i think the truth is that most folks are unable to out drive their car,

don

qft

[stab6902]

Promote away. The flip side of that is you have to support your assertation..... or facts.

Read the OP and tell me what your 3 link does better than the Quadralink for that application.

For the record, I like you and your product and I believe this place and the hobby/industry is better with you in it.


I'm totally with you on all three points.

95%+ of pro-touring enthusiasts don't track their cars - just like relatively few people track their their Vettes, Porsches, etc. As such, trading a tiny bit of ultimate performance for ride comfort, packaging, and durability is well worth it.

By the way, I have no affiliation with DSE (or any other aftermarket company), but as evidenced by their growth, they know the market.

[Mark@lateral-dynamics]

Heading out for a wedding, so here are the main attributes:


Easier to install than brand D. No need to hack out the better part of the trunk.
Fully adjustable, if you want to play with the geometry, you can. Roll center height, anti-squat/lift, roll axis, etc, broadest adjustment range in the industry - by far. Also simple to set and forget with exceptional all around performance and comfort.
TONS of room for tailpipes.
Watt's Link creates ZERO roll center migration, PHB's do not (granted, migration is not large, but still).
Zero bind beyond the wildest excursion of suspension travel. I'll snap a pic this weekend, you could go rock crawling with the amount of bind free articulation.
Shock agnostic, you go with any suitable length shock. For the very best value of performance to dollar, Viking Triple's are our recommendation. JRI makes an excellent shock, but there are lots of other excellent options out there that we don't tie you down to.
Sway bar agnostic, practically any OEM style unit will work.
Very cool appearance. Style points for D and E in the USCA events.
Made in USA, supports our local economy with virtually all components sourced within 50 miles of our So Cal location. Veteran owned - proudly.
"Touring" version offers extremely capable rubber bushings (main links) to knock down NVH, while still preserving full bind free articulation.
Considering the extra cost of installation and the price of the actual kit, we come out ahead in dollars/time spent.
And so on. You can get more details from our "Introduction" thread within this forum.


I'd like to pose the question back at you guys. WHY, specifically, is the DSE Quadralink better than the Lateral Dynamics Next Generation 3-Link? In fairness, DSE has an extremely large and loyal following which they can be proud of. We do not. So, when we post here or other places, we are immediately outnumbered by the "competition." Respectfully, DSE's office supply budget is probably larger than our entire product development budget, but I challenge you to find an operation that does more, with the same or less available resources. Not complaining, but when you put your entire life into something, work extremely hard and produce a superior product - only to get dumped on by naysayers..... well no one said it was fair. And that's okay.

In the end, we produce an excellent option for folks just like the OP, and many others.

Thanks, and be well.

[dontlifttoshift]

Easier to install than brand D. No need to hack out the better part of the trunk.

I mean, at least you get metal to close it out with. That's dead space anyways and it's kind of nice to have it all flat and stuff when you are done.




Fully adjustable, if you want to play with the geometry, you can. Roll center height, anti-squat/lift, roll axis, etc, broadest adjustment range in the industry - by far. Also simple to set and forget with exceptional all around performance and comfort.
Cool!



TONS of room for tailpipes.
Can I buy an off the shelf exhaust kit to bolt on?



Watt's Link creates ZERO roll center migration, PHB's do not (granted, migration is not large, but still).
True, but as noted, minutia.....especially for street car.



Zero bind beyond the wildest excursion of suspension travel. I'll snap a pic this weekend, you could go rock crawling with the amount of bind free articulation.
Cool!.....but 5* is typically max.



Shock agnostic, you go with any suitable length shock. For the very best value of performance to dollar, Viking Triple's are our recommendation. JRI makes an excellent shock, but there are lots of other excellent options out there that we don't tie you down to.
The single shear lower mounts can be problematic when the shocks bottom.



Sway bar agnostic, practically any OEM style unit will work.
Ability to use existing parts is a plus.



Very cool appearance. Style points for D and E in the USCA events.
Debatable. Looks are subjective and not like D&E matters in this case.



Made in USA, supports our local economy with virtually all components sourced within 50 miles of our So Cal location. Veteran owned - proudly.
Well done and Thank You!



"Touring" version offers extremely capable rubber bushings (main links) to knock down NVH, while still preserving full bind free articulation.
Still 4 sphericals in the watts though?



Considering the extra cost of installation and the price of the actual kit, we come out ahead in dollars/time spent.
Can't argue that.


I'd like to pose the question back at you guys. WHY, specifically, is the DSE Quadralink better than the Lateral Dynamics Next Generation 3-Link?

Rubber at all link connections, sphericals only on the shocks. Quiet for life and zero maintenance.

Completely closes out all protrusions into the cabin and works with slightly modified back seat.

PHB is the ultimate in simplicity. I will admit that I think their roll center is too high.

Personal experience with the product has been positive and I know that after properly installed I will never have to think about it again.

I can be reasonably sure that Detroit Speed will answer the phone in 5 years.



In fairness, DSE has an extremely large and loyal following which they can be proud of. We do not. So, when we post here or other places, we are immediately outnumbered by the "competition." Respectfully, DSE's office supply budget is probably larger than our entire product development budget, but I challenge you to find an operation that does more, with the same or less available resources. Not complaining, but when you put your entire life into something, work extremely hard and produce a superior product - only to get dumped on by naysayers..... well no one said it was fair. And that's okay.

Really? No one is dragging you and I have no interest in doing so. I made a recommendation as requested by the original poster. The critiques of your product in this post are per your request.

Like I said, I like the product. Have a good time at the wedding!

[stab6902]

WHY, specifically, is the DSE Quadralink better than the Lateral Dynamics Next Generation 3-Link?

To start, let me reiterate that I think the DSE QuadraLink is better for the OP's application. As a reminder, he prioritized ride comfort for a car only driven on the street. And, I'm comparing the QuadraLink to the all heim joint 3-link pictured in your other thread. From what I gather, your rubber bushing "touring" version is still in development.

Here's why I'd recommend the QuadraLink for anything other than a race application:

Rubber bushings - as I've said a couple times now, these are important for reducing NVH and impact harshness. Additionally, they're more durable in a street application. I don't like the idea of road grit, water, etc getting into the spherical bearing and creating wear/noisy slop. In my mind a good street suspension has zero heim joints.
OEM quality appearance and integration - this one is mostly preference, but the DSE system looks more tidy and "factory" to me, as opposed to your more aftermarket/race look. I'm personally not a fan of the "shift boot" on your upper link.
Packaging - again, the DSE just looks cleaner and more compact, and it appears to have more room for mufflers and tailpipes.
Rear seat - you can use the factory rear seat with the DSE system. Not sure about your setup, but it looks like some modification would be necessary.
Documentation - DSE has a well documented installation manual, videos, etc. Not sure where you're at with that.
Known quantity factor - lots of people are running the DSE system and know how to set it up, good brand recognition/resale value, etc.
"Matching" front suspension available - sounds like you have this in the works too.


For these reasons the DSE system gets my nod at the moment. Maybe that will change once your "touring" version is ready to ship.

If you're wondering, here's my wish list for the "touring version":

Rubber bushings everywhere - the MetalCloak bushings look interesting; might take some R&D to get the durometer just right
Panhard bar rather than watts link - a 43" long panhard bar moving +/- 2" results in less than 0.1" lateral movement. That's good enough for me.
Fully enclosed top link rather than shift boot
Make as much of it bolt on as possible - BMR and Ridetech do a good job of this, and lots of people would prefer to use their existing axle
Lower price - reasonable expectation since you'd be reusing the stock type axle and a panhard bar



Again, I'm in no way trying to knock your product and I think it's great for a race application. I have a lot of respect for you and your company. Not sure if it comes through, but I'm truly trying to be honest and helpful here.

[stab6902]

The critiques of your product in this post are per your request.


You must be a faster typer than me, Donny. We're on the same wavelength.

[AEH]

Wow. Some excellent information and responses here. When I made My original post I neglected to Subscribe to it and when I came back to check it it was gone. I realize I posted in the wrong place and the moderator must have moved it but I just assumed it got deleted. Still searching for answers I found it again this morning.

I realize this is just another "how can I have my cake and eat it too thread" but the challenge is REAL for those of us who don't have years of experience with suspension design and a vast experience base to draw from. You hope to only do this once and not screw it up. As an Example: Read the classifieds and see how many jeeps you see with "all brand new wheels, tires and a new 6" lift". Why would someone spend $10,000 on new parts and then just sell their Jeep. Cause now drives like crap. A bad combination of good parts. I'm trying not the be that guy, lol.


When I was a kid and you wanted to figure how to do something you had to find and expert. If you couldn't find an expert, you went to the library and started going through the "Popular Mechanics Magazines". The Internet is an incredible tool and has made access to information so prevalent the question is now more often, "why" instead of "how.

I had narrowed my selection originally down to Two. Either the DSE 4-Link or the Speedtech Torque Arm. I originally didn't post brands because I hoped the discussion to be about differences in the two technology and not any one brand over another.

I chose the DSE over the other available 4 links because of the geometry. Instead of constraining the geometry of the upper links to the available space, they "increased" the space to fit the geometry with the upper link pockets. I also like the fact that they raise the upper shock mount at or above the original sheet metal by extending the frame rail connectors into the interior of the trunk. The higher the top mounts, the less the bottom mount hangs down. My only real hesitation with the DSE is my limited experience with 4 links. Anything I ever rode in, except production based vehicles, was loud and harsh. In fairness, they weren't built to ride in, just to go fast, but still my experience is limited.

In the torque arm category I liked the Speed Tech. My major hangup with it is the fact that the Torque arm hangs down below the 3rd member all the way from the axle to the center of the car. It may all be in my mind and not be an issue at all but I don't want to be dragging on speed bumps. Also the aforementioned X-Pipe limitations.

I do appreciate all the advice and hope to see more.
Mike

[Rod]

fun thread....

[chevelletiger]

^^ Agree 100% Rod.

[Vimes]

Wow, did this snowball right on down the hill. :razz:

The best part for the job will always depend upon the job. Let's remember what the OP was looking for.

"My intent for the car is to build a very nice cruiser we can drive anywhere we want to go and still enjoy the ride. I don't want to be cussing it after 8 hours or have to argue with the wife whether or not we take the Camaro on the next trip. I realize everything is a compromise but I want all the performance I can get without sacrificing ride. I will never track the car and it'll never see the drag strip. I want it to be fast and capable and there will be times I'll push it, but I'm not trying to win any titles or even compete. It's just gonna be My Car. I'll get the best seats I can find, use all the sound dampening and Insulation I can get in it and probably soften whatever suspension I end up with."

Based on his stated requirements, that's a very easy decision, torque arm. A 4-link is primarily a drag racing suspension, and it was not designed with canyon carving in mind so would probably not be the best for spirited driving. A torque arm is mostly bolt-in with very little welding required, may at most require that his exhaust be moved a little, and will give him the ride and all-around street performance he's looking for. And, as he wants it for when he and the wife travel, the wife would likely not find the car hard to handle should she get behind the wheel. That BMR setup looked pretty nice.

Oh, and hey - on the seats, look into "suspension seats." If they can let guys jump 200ft at 100MPH running desert dunes without driving their a&&holes through their necks, they should be very comfortable on the street. These are the ones (https://corbeau.com/baja-xrs/) I plan to run in my truck if I can ever get my project off the ground. I sat in one at a shop and was very impressed at how comfortable they were, and the wife (who had a spinal fusion) also found them very comfortable on her back.

[CSG]

vimes. I assume your truck is not an off-road vehicle? Lots of broken backs from suspension seats in Offroad race trucks, I only mention it because I would not want your wife injured but if it’s a street vehicle then by all means carry on.

I like Mark’s 3 link but his statement about 4 links handling like crap rubbed me a bit. I have modeled a lot of 4 links and yes of course there is some bind but not always that much. I’ve also set pole a bunch of times with one of those crappy handling converging 4 links with a panhard bar...

I want to add to this that I do prefer 3 links and torque arms and have had all 3 designs on the same car, but the statement came off to me as knocking the 4 link much more that it really shows up in the real world.

[Rod]

A 4-link is primarily a drag racing suspension, and it was not designed with canyon carving in mind so would probably not be the best for spirited driving.


ha ha ha ha ha ha that's the funnest thing I ever heard.... leaf spring, 3 link, 4 link, torque arm, z-link, IRS, all do the same thing, how they get there is what makes them different, how the geometry is completed and the platform they are installed on that affects the result...

[Vimes]

vimes. I assume your truck is not an off-road vehicle? Lots of broken backs from suspension seats in Offroad race trucks, I only mention it because I would not want your wife injured but if it’s a street vehicle then by all means carry on.

Yeah, I'm doing a street machine. Personally I think those guys that go dune cruising are nuts because the risk/reward formula is weighted way, way too far in the risk category, but the premise holds about the seats. If they can handle extreme off-roading, even if some of the more spectacular jumps result in spine damage, they should do a fine job of cushioning bumps on the street. Plus, they actually are pretty comfortable to sit in.


ha ha ha ha ha ha that's the funnest thing I ever heard.... leaf spring, 3 link, 4 link, torque arm, z-link, IRS, all do the same thing, how they get there is what makes them different, how the geometry is completed and the platform they are installed on that affects the result...

So your claim is that no suspension has compromises, and all do an equal job at everything?

[Mark@lateral-dynamics]

I like Mark’s 3 link but his statement about 4 links handling like crap rubbed me a bit. I have modeled a lot of 4 links and yes of course there is some bind but not always that much. I’ve also set pole a bunch of times with one of those crappy handling converging 4 links with a panhard bar...

Far enough, but let me temper the statement a bit. I always default to solid type bushings when I look at a setup. Years back, a buddy had an old school four link with PHB that was setup as a pro street car. When he put pro touring type wheels and tires, the car became basically undriveable. The negative issues with the overall setup was masked by the previous really tall, loose sidewall tires. Solution in his case was a simple as removing one of the upper links, transformed the car completely with no other changes, and it got better from there with additional tuning. This car was all rod ends and it couldn't easily be changed, and didn't need to in the end. So, that was what was happening in my brain and translated to my statement. Hence, this is also why I made the statement about the rubber bushings. Fair?

[Mark@lateral-dynamics]

@ Donny and Ryan: THANK YOU!!!! for the feedback. Greatly appreciated. Yes, we still have some items to finish up such as the install instructions, indeed the UCA area WILL be covered with a sheet metal cover, etc. The Duroflex bushing are already proven, we already have thousands of miles on them personally. Ironically, on applications that are four links with PHB'S!

Cheer, and again, thanks.

[Rod]

So your claim is that no suspension has compromises, and all do an equal job at everything?

nope that's what you said... what I said is


ha ha ha ha ha ha that's the funnest thing I ever heard.... leaf spring, 3 link, 4 link, torque arm, z-link, IRS, all do the same thing, how they get there is what makes them different, how the geometry is completed and the platform they are installed on that affects the result...

rear suspension has 3 basic functions 1) weight control (hold the car up) 2) Lateral location 3) axel location

and to answer that now asked question.. they are all a compromise .......

[Vimes]

nope that's what you said... what I said is



rear suspension has 3 basic functions 1) weight control (hold the car up) 2) Lateral location 3) axel location

and to answer that now asked question.. they are all a compromise .......

In that case, I'm glad we agree, and that you got a laugh from it to boot. The 4-link compromise is it gives up handling performance in favor of straight-line performance. A torque arm gives up excelling in any one area to be a decent street suspension that is competent in multiple areas, which is why I still feel the OP would be better off with one. He's not drag racing, and he wants something comfortable for long drives that will keep his wife happy. :twothumbs

[dontlifttoshift]

4) drives the car forward. That one is pretty important.

Vimes, have you driven on any or all of these rear suspensions? Not looking to validate or invalidate your opinion, just curious about your background and the foundation that you are forming your opinions on.

[dhutton]

I’m no expert but don’t we have to differentiate between parallel four link, converging four link and canted/triangulated four link suspensions in this discussion?

Thanks,
Don

[Vimes]

4) drives the car forward. That one is pretty important.

Vimes, have you driven on any or all of these rear suspensions? Not looking to validate or invalidate your opinion, just curious about your background and the foundation that you are forming your opinions on.

No worries. I currently own two vehicles with 4-links, one is a 2015 Tahoe and the other is a 1970 Chevelle. I've owned about 40 different cars over the last 35 years with just about every suspension commonly used in the US. Oddly enough though, I've never owned a torque arm car. However, that's about all my brother has owned since the 4th gen Camaro has come out, so I've driven one often enough to know how they handle.

Disclaimer, I've never competed in any organized events before. I don't doubt that I could do well, but I'm not willing to invest the time or money into it.

[Sleeper68]

I’m no expert but don’t we have to differentiate between parallel four link, converging four link and canted/triangulated four link suspensions in this discussion?

Thanks,
Don

Absolutely. Lumping all under "4 link" is really a gross generalization

[Mark@lateral-dynamics]

So, we decided to throw an empty housing under the shop car to show the amount of available suspension travel before bind. We have, from the very beginning emphasized "zero bind" with our setup so here are a couple pic's to show what we mean by that. This housing is empty so we didn't have to deal with the admittedly very heavy center section, axles, and brakes. The suspension articulates like butter. Silk. Gorilla snot, or any other super slippery medium you choose. Driver's side is 6" off of the deck, while the passenger's side is 24 inches. Inches, not millimeters. This is what "we" call zero bind.

Who cares? We do. And here's why. Performance vehicles rely upon precise tuning in order to operate at their very peak. With (for all intents) zero friction, the setup relies completely upon the springs, shocks, and sway bar to manage both the steady state and dynamic inputs. OEM type rubber joints, for instance, have an increasing "stiffness" in roll/bump by their very nature. At some point, they go full stiff, and that typically results in an abrupt reaction. Ever drive a fox body Mustang in anger? Once the bushings compress to their limit, the setup effectively locks up, and you get snap oversteer. I have personally had several of those cars and LOVE them, but that's no bueno. Especially in the wet.

I challenge anyone that has a five link type setup (i.e. parallel four link with PHB or Watt's) to do this same experiment and show the same outcome.

Yes, we are very passionate about our approach, but again, it's not marketing hype - it's based on physics and engineering. That's the same thing that race teams do at all levels. And it's the same thing the OEM's do too, all with exceptional success. It's just the target requirements that are different.

For the record, this is with all Heim/rod ends. I guarantee the same results with the same rubber (NHV isolating) bushings we have chosen to go with, I drive on them every single day.

Take care, be well.

[Mark@lateral-dynamics]

The single shear lower mounts can be problematic when the shocks bottom.

Please calculate the shear strength of a 1/2", 150 kPSI Grade 8 bolt, and explain with data, how this can be problematic. And I truly mean this respectfully.

[CSG]

I agree on the snap oversteer. My first experience with it was in a fox as well. I was tasked with driving a car I had zero experience in with no practice lap. The particular car handled very well until it didn't. When the rear went full stiff it did exactly what you would expect, luckily I had enough track to chase it. I have not had that same result though with a "proper" designed 4 link & bar. As stated above we can't lump all 4-links together. Since you are/were into foxes as well have you driven one with the original (not second generation) Steeda 5 link? For those unaware this is a redesigned 4 link with panhard bar for fox mustangs. It was a bolt-on deal with no floor cutting or anything so it was still a compromise setup but it worked really well.

[stab6902]

Please calculate the shear strength of a 1/2", 150 kPSI Grade 8 bolt, and explain with data, how this can be problematic. And I truly mean this respectfully.

I was curious, so I consulted google and did some quick and dirty math.

According to the internet, potholes can cause 30g+ vertical acceleration: "Pothole events that cause jounce bumper impacts can impart over 30 g's vertical acceleration (measured on a control arm near the ball joint). Those same events will produce over 3000 lbs longitudinally (at the tire patch)." Source: https://www.eng-tips.com/viewthread.cfm?qid=149427

So if you hit a gnarly pothole that resulted in metal to metal contact on the coilover assembly, (i.e. bottoming the shock without a jounce bumper or coil bind), that 30g's would be transmitted through the shock bolts. We can't really rule out metal to metal contact since it's up to the customer to pick suitable springs, shocks, and jounce bumpers, and I don't trust the average hot rodder to get that right 100% of the time.

Assuming a rear corner weight of 800 lbs, 800lbs*30g's=24,000 lbs shear force on that shock bolt. The 800 lb corner weight assumption is actually on the low side, especially if you want to consider load transfer.

According to Fastenal, 1/2"-20 grade 8 bolts have a shear strength rating of 13,376 lbs. Source: https://www.fastenal.com/en/84/load-calculator

Since 24,000>13,376 lbs, it appears Donny's concern (probably rooted in experience) is warranted for a street car.

[Mark@lateral-dynamics]

Since 24,000>13,376 lbs, it appears Donny's concern (probably rooted in experience) is warranted for a street car.

Except there are TWO bolts holding the car up, on each side. Also, the spring and damper consume the overwhelming majority of that impact force (even if 30 G's is stupid conservative), BEFORE the shock goes into bind, hits the bump stops, etc. The tire also compresses. And so on.

But appreciate the effort! At the same time, this is a good example of (even though well intentioned) misinformation that folks need to be wary of.


Since you are/were into foxes as well have you driven one with the original (not second generation) Steeda 5 link? For those unaware this is a redesigned 4 link with panhard bar for fox mustangs. It was a bolt-on deal with no floor cutting or anything so it was still a compromise setup but it worked really well.

I had a good amount of experience with those cars, and have a small Army of buddies who raced them extensively in NASA American Iron. I haven't driven the Steeda stuff, but did install a PHB to otherwise stock rear on my '89, it was a lesser brand but I didn't know any better. It tightened up the car a bit, but didn't really make it "better," until it broke. The battle of roll center location was won by the factory convergent 4 link. When I returned it, they weren't surprised at all, pretty much all of them were breaking. For the life of me I can't recall who they were, located in Orange County, CA.

[stab6902]

Except there are TWO bolts holding the car up, on each side.

I considered that in my calculation - I assumed a (low) corner weight of 800 lbs. If you mean there's one bolt on each side of the coilover, they're in series, and the top one is in double shear, so the bottom one would "feel" the whole load.


Also, the spring and damper consume the overwhelming majority of that impact force

My point was that since you leave it to the customer to choose the proper shock/spring/bump stop combination, you have to consider the risk that they get it wrong. There's plenty of posts on here where people have issues because they're running shocks with too little travel, coil bind, no bump stop at all, etc. People like running their cars low and not everyone is a suspension expert.


(even if 30 G's is stupid conservative)

What have you measured? I don't have any test data and had to resort to the internet. Obviously the pothole situation is much more of a concern for street cars, so typical racecar numbers don't really apply.


BEFORE the shock goes into bind, hits the bump stops, etc.

Agreed, as long as the proper spring/shock/bump stop is chosen, there will be no issues at all.


The tire also compresses.

From what I gather, the 30+g was measured on a real vehicle hitting a real pothole (so the tire was accounted for).


But appreciate the effort! At the same time, this is a good example of (even though well intentioned) misinformation that folks need to be wary of.

I think my point is still valid - if someone specs the wrong coilover and it bottoms out hard, that lower bolt will break. I've heard of it happening on much lighter weight street rods. Really, if there's going to be a "fuse," that's one of the better spots to have one. I still think your design looks fine - you just need to be careful to coach your customers to buy the right coilovers or you might have warranty issues.

[Mark@lateral-dynamics]

I follow your logic, but fortunately, (and respectfully) some of it isn't correct.


If you mean there's one bolt on each side of the coilover, they're in series, and the top one is in double shear, so the bottom one would "feel" the whole load.

This is incorrect. The forces are indiscriminate, both sides of the shock see exactly the same force (neglecting the mass of the shock, which is insignificant when considering the magnitude of the vertical force). IF, and a very big IF, the forces are high enough to shear off one of the bolts, you are correct that one in single shear will go first as both are the same bolts.

Hitting a curb/pothole straight on produces a force vector, your assumption is that ALL of the impact is going only vertical, but there is (just about as large) a longitudinal force trying to push the wheel back as well. As such, the vertical force is approximately only half of the total impact force. "Half" of the force is reacted through the combination of LCA's and to far lesser extent, the UCA. I say approximately because it depends upon how deep the pothole is, the deeper it is, the higher it will contact the rim, and less vertical load relative to the longitudinal.

Also, your assumption that the lower BOLT will see 30 G's is way over-estimated. If you see that type of a load on anything on a car, you no longer have a car, and are also probably in seriously bad condition, or dead. The 30 G factor is an impact load imparted on the TIRE. It travels through the tire, into the rim (which in this case is now destroyed), into the axle, through the wheel bearing, lifting half a 250 lb axle assembly, which directs the load into the spring/shock assembly. 30 G's is the type of impact a 200 MPH race car sees when hitting the wall. They usually don't survive that.

By the way, we are not the only ones who single shear a shock mount, I don't think too many people would bash on Ridetech, for instance?

We don't let the shock selection completely up to the customer. We leave the SUPPLIER of the shock up to them. The dimensions for the actual shock depend upon the static ride height, and we include a set of guidelines to consider when selecting the proper shock and spring length. The last thing we would ever, ever, ever do is to leave a customer, who trusts us enough to buy our system, hanging with a critical decision such as this.

Hope that helps.

[stab6902]

The forces are indiscriminate, both sides of the shock see exactly the same force (neglecting the mass of the shock, which is insignificant when considering the magnitude of the vertical force). IF, and a very big IF, the forces are high enough to shear off one of the bolts, you are correct that one in single shear will go first as both are the same bolts.

We're in total agreement. In my example, each shock bolt would see the 24,000 lb load, just like each link in a chain sees the same load (neglecting the mass of the shock or links respectively). The load doesn't get "split up" if you add bolts or links in series.


Hitting a curb/pothole straight on produces a force vector, your assumption is that ALL of the impact is going only vertical, but there is (just about as large) a longitudinal force trying to push the wheel back as well. As such, the vertical force is approximately only half of the total impact force. "Half" of the force is reacted through the combination of LCA's and to far lesser extent, the UCA. I say approximately because it depends upon how deep the pothole is, the deeper it is, the higher it will contact the rim, and less vertical load relative to the longitudinal.

The guy on the other forum explicitly stated the z-component of the acceleration (vertical only) was measured at 30 g.


Also, your assumption that the lower BOLT will see 30 G's is way over-estimated. If you see that type of a load on anything on a car, you no longer have a car, and are also probably in seriously bad condition, or dead. The 30 G factor is an impact load imparted on the TIRE. It travels through the tire, into the rim (which in this case is now destroyed), into the axle, through the wheel bearing, lifting half a 250 lb axle assembly, which directs the load into the spring/shock assembly. 30 G's is the type of impact a 200 MPH race car sees when hitting the wall. They usually don't survive that.

I figured there would be some pushback on the 30 g figure. Honestly my gut reaction was the same, but not having any data of my own, I'm an innocent until proven guilty kind of guy. He said the 30 g's was measured near the ball joint (1:1 ish motion ratio). My understanding from reading the thread was that this was measured on a real car hitting a real pothole, and I have to assume that car had tires. If you read the spec sheet of the wheel force transducers he references, the "passenger car" sized model measures Fz up to 11,000+ lb, and that's at the wheel, not the tire.

According to wikipedia, Indy car crashes are in the 200 g range, and somebody survived a 214 g crash. Source: https://en.wikipedia.org/wiki/G-force


By the way, we are not the only ones who single shear a shock mount, I don't think too many people would bash on Ridetech, for instance?

Nobody is bashing on anybody. I know your product means a lot to you and the last thing I want to do is discourage innovation in our hobby. Ridetech didn't ask anyone on here to run any calculations, and they use a 5/8" stud on their lower single shear shock mount. 5/8" bolts have over 60% more shear strength than 1/2" bolts. BMR also uses 5/8" bolts on their lower coilover mount. Maybe they're onto something.


We don't let the shock selection completely up to the customer. We leave the SUPPLIER of the shock up to them. The dimensions for the actual shock depend upon the static ride height, and we include a set of guidelines to consider when selecting the proper shock and spring length. The last thing we would ever, ever, ever do is to leave a customer, who trusts us enough to buy our system, hanging with a critical decision such as this.

Glad to hear it! Judging by your responsiveness on this forum, I'm sure your customer service is great.

[Rod]

4) drives the car forward. That one is pretty important.



ok ok ok yes forward motion... dang all picky



40 different cars over the last 35 years

Car dealer?

[Vimes]

Car dealer?

No, I've just been around for a long time.

[raustinss]

Im glad that Ryan brought up the topic of the indy car crash which ,is funny because immediatelythought about that crash i believe Emerson (not going to butcher rhe last name lol ) was the driver or had one similar. Regardless as to what the forces are or arent on a bolt, its the amount of time the bolt is stressed with those forces that determines if the bolt breaks or not . I would say clearly there's a mistake in calculation somewhere or we would be hearing about suspension failure due to broken bolts all the time yes ???

[stab6902]

To be clear, my back of the napkin math represented the extreme worst case. I'm guessing the engineer who quoted the 30 g figure worked at an OEM, and the test was probably done on a proving ground. I've ridden along on a few durability loops (as a passenger during training), and it's amazing how abusive they are, both to the cars and the driver. We're talking impacts that would put big dents in the rims of the average pro-touring car.

In addition to an extremely hard hit, the coilovers would have to be in mechanical bind (coil bind or bottomed out with no bumpstop) to see that kind of load. If you choose your coilovers correctly and are running some kind of bumpstop, you'll never have that problem. Like I said, extreme worst case.

A lot of people can and do get away with 1/2" coilover bolts in single shear, but it wouldn't be my first preference. You don't hear about it often, but they do fail in the real world. Some discussion on it here: https://www.jalopyjournal.com/forum/threads/broken-coil-over-bolt-question.991025/

If I were building a coilover car, I'd go with 5/8" bolts if I had to do single shear, which is what most aftermarket companies do anyway. The shear rating of a 5/8" grade 8 bolt is very close to the "worst case" I calculated. The theory (crude as it is) seems to line up with real world experience and best practices.

[dontlifttoshift]

Please calculate the shear strength of a 1/2", 150 kPSI Grade 8 bolt, and explain with data, how this can be problematic. And I truly mean this respectfully.


I know what the math says and I really don't care what the math says.

In the past 20 years I have a handful of real world instances on street cars, not race cars, where the bolt in a single shear lower shock mount failed. When those bolts bent or broke they did not care that mathematically they weren't supposed to. Most of those were 5/8" in diameter as well in a street rod application. We can point to a number of factors for the failure but the fact remains that they failed.


My personal RideTech equipped 71 Camaro still has the factory bump stops on the rear frame rails above the axle.

[dhutton]

I know what the math says and I really don't care what the math says.

In the past 20 years I have a handful of real world instances on street cars, not race cars, where the bolt in a single shear lower shock mount failed. When those bolts bent or broke they did not care that mathematically they weren't supposed to. Most of those were 5/8" in diameter as well in a street rod application. We can point to a number of factors for the failure but the fact remains that they failed.


My personal RideTech equipped 71 Camaro still has the factory bump stops on the rear frame rails above the axle.

So what is the design solution for these failures? It seems they are all done this way.

Don

[stab6902]

So what is the design solution for these failures? It seems they are all done this way.

Don

I totally believe what Donny says regarding even 5/8" bolts failing. We didn't even talk about fatigue yet... lots of smaller hits can do the same damage over time.

The best solution is to run the factory style bump stops between the axle and frame rail like Donny said. Cycle the suspension without springs, and make sure the bump stop is really what limits travel.

[Sleeper68]

So what is the design solution for these failures? It seems they are all done this way.

Don

The solution? Double shear mounting. What hasn't been brought up yet is what makes single shear mounting a real killer: Moment loading. What is a moment? Essentially a torque. Yes the fastener will see a shear load, but it will also see a torque. Fasteners are not designed to be loaded in moment and shear (also known as complex loading). The moment has a tendency to bend the bolt, sometimes it is called a bending moment because of this.

Here's an excerpt from an airplane design guide:




Single Bolts in Single Shear:

There are some joints in airplanes which must be held together with a single bolt. Some examples of these are strut-end attach points and bracing-wire attach points.

There are two types of bolted or pinned joints. The first is a single-shear joint, where the bolt goes through each of the parts to be joined only once and is loaded in shear at one point along its length. The bolt is tightened to clamp up against the two parts being joined.

The second type of bolted joint is a double-shear joint, where one part forks around the other and the bolt goes completely through both the fork and the part within the fork. In this joint, the bolt is loaded in shear at two points. The bolt in a double-shear joint may be clamped up, but it is not necessary for the stability of the joint.

While both types of joint can be used safely in some applications, there are some significant problems with single-shear joints; they should be avoided in highly-loaded and flight-critical areas wherever possible.

The first problem with single-shear bolt installations is that the bolt carries all of the load at the single-shear plane. If the same bolt were installed in double shear, it would be able to take twice the load because the load is shared between the two shear planes in the double-shear joint. This, in and of itself, is not dangerous as long as the bolt is properly sized to take the loads it must carry.

The second problem is more severe, and is the primary reason single-shear joints should be avoided in critical areas. A double-shear joint is stable. If the nut loosens, and the bolt moves in the hole, a double-shear joint remains in place, and the internal loads in the joint do not change. The joined parts do not move relative to each other because one is captured by the fork in the other. As long as the bolt still goes all the way through the fork, the strength of the joint is not compromised and nothing shifts undesirably.


A single-shear joint, on the other hand, is dependent on the clamp-up of the nut and bolt head for stability. If the nut loosens, the two bolted-together parts can move apart. If a gap forms between the two parts, the load carried by the bolt is no longer carried in pure shear. The gap provides a lever arm for the forces on the bolt, which then exert bending moments on the bolt and the bolted parts. These moments can bend both the bolt and the bolted parts. The bending causes the bolt to upset and tend to align itself with the forces on the joint. This can cause the gap to open further, and thus increase the moments. This situation is unstable, and will often lead to large distortion, or failure of the joint. Both are highly undesirable, and potentially dangerous.

Single-shear attachment of bracing wires seems to be a relatively common error, particularly among the designers of ultralight and low-performance light airplanes. It is very simple to attach a wire to a tang and simply bolt it to the hard structure. The airplane I mentioned last month as having multiple potential single-point failures in its tail had the tail bracing wires attached this way. Even more frightening was the fact that the tail was not only braced by these wires, but held onto the airplane by tensioning them. A small loosening of the bolt in the single-shear tail-wire attach joint on this airplane could cause the bracing wires to loosen and lead to the departure of the tail.

The proper way to attach bracing wires and control cables is to put a fork on the end of the wire and attach the fork to a tang on the structure or the control horn with a properly-safetied bolt or clevis pin in double shear. Strut-attach and wing-attach fittings should always be designed so they bolt together with the bolt in double shear.



In the case of the coilover mount, the load is always applied at distance from where the bolt is fixed to the mount. This distance imparts the greater load (moment load) in addition to the already doubled shear load.

"there are some significant problems with single-shear joints; they should be avoided in highly-loaded and flight-critical areas wherever possible." - Take this to mean: avoid single shear fastening in suspension components whenever possible as it is ride and safety critical

To summarize: Not only does double shear reduce the shear stress to half of that of single shear, it also reduces the bending moment because each end of the bolt shares (reacts) the moment.

It is a simple task to change the lower coilover mount to double shear. The cost is minimal, the safety factor increase is immense. I think the choice is clear.

Attached is a picture of an easy way to change to double shear. FYI, DSE uses fasteners in double shear for their upper and lower coilover mounting on the quadralink.

[dhutton]

Ok thanks for the tech. Apparently I didn’t understand single versus double sheer but now I do.

Thanks,
Don

[dontlifttoshift]

......and like everything in hot rodding. It still comes down to packaging and the compromises that go with it.

The mounting bolts typically run parallel to the axle in a double shear and perpendicular to the axle in single shear. In a single shear, if your upper and lower mounts aren't in line (side view) and/or you have significant pinion angle change through travel, the bearings will bind. In double shear, the mounts need to be in line (rear view) so they don't bind in roll. So your shocks end up vertical, which in itself is not an issue. However, a 4" stroke shock laid over at 15* gets you nearly 5" of wheel travel and a shorter overall package. That's a win.

It is also far easier to fabricate and assemble a single shear mount and certainly easier to adapt to the plethora of coil over shocks that are available in the hot rod aftermarket.

In general, it's a fair trade and one I am willing to make for some applications but it is worth the time to assemble something better than crashing the shock together hanging off of a 1/2" bolt. Like a frame mounted bumpstop, or jounce bumper if we want to keep speaking engineer.

Worth noting, I am speaking generally about all single shear shock mounts or coil over mounts, not just the LD.

[badazz81z28]

In all honesty....I have driven in Camaros with most of the variants and I really couldn't tell a difference....The quality, cost, ease of install are more important factors. For example a torque arm kit would wreak havoc on my exhaust system.

[Rod]

There are good reasons GM went with a torque arm. That being said it's more about finding the right spring and shock combination to reach your goals.

packaging... the torque arm allows more interior room, allowing you to have a back seat, thats why packaging a for link in a second gen camaro is a pain in the ass, there is no room under the car without cutting into the floor... same with 3rd gens and thats why GM used a torque arm

[Rod]

What hasn't been brought up yet is what makes single shear mounting a real killer: Moment loading. What is a moment? Essentially a torque. Yes the fastener will see a shear load, but it will also see a torque. Fasteners are not designed to be loaded in moment and shear (also known as complex loading). The moment has a tendency to bend the bolt, sometimes it is called a bending moment because of this.




ohhhh we are getting all booky and stuff.. fun, let me get a beer and sit down

180917

[Mark@lateral-dynamics]

fun, let me get a beer and sit down

Can you please save one for me too! Or three?

[Rod]

Can you please save one for me too! Or three?


ha ha ha ha,,, beer that man

[Rsj4h]

packaging... the torque arm allows more interior room, allowing you to have a back seat, thats why packaging a for link in a second gen camaro is a pain in the ass, there is no room under the car without cutting into the floor... same with 3rd gens and thats why GM used a torque arm
What are the thoughts of Ridetech triangulated 4link versus a Speedtech torque arm in a second gen for street driving? Minitubbing so leafs are out. I have been debating on the two and want a comfortable ride first, with handlinga close second. I’m doing full off restomod with around 400hp, so exhaust will be replaced either way as I know both require a different approach. With the Ridetech I’d probably reuse my 10 bolt, but with the torque arm probably better to just bite the bullet with a 9”...$$

Would Ridetech require the optional sway bar for street?

Does the triangulated or panhard location devices perform better for street?

Thanks!

[BMR Sales]

Watts Link all day long

https://static1.pt-content.com/images/pt/2021/05/differencespanhardbarwattslink2018122322-1.gif (https://postimages.org/)

[BMR Sales]

https://static1.pt-content.com/images/pt/2021/05/Wattslinkage-1.gif (https://postimages.org/)

[stab6902]

What are the thoughts of Ridetech triangulated 4link versus a Speedtech torque arm in a second gen for street driving? Minitubbing so leafs are out. I have been debating on the two and want a comfortable ride first, with handlinga close second. I’m doing full off restomod with around 400hp, so exhaust will be replaced either way as I know both require a different approach. With the Ridetech I’d probably reuse my 10 bolt, but with the torque arm probably better to just bite the bullet with a 9”...$$

Would Ridetech require the optional sway bar for street?

Does the triangulated or panhard location devices perform better for street?

Thanks!

Hard to say if you'd need to run a rear sway bar with the Ridetech system... depends on a ton of variables like spring rates, front sway bar rate, roll center heights, weight distribution, tire stagger, etc. If you shared details about your car, some people with similar setups might chime in. Or better yet, call Ridetech and ask them directly.


I think Watt's links are cool, but in the real world I can't imagine anyone could feel the roughly 1/16" of lateral movement caused by a panhard bar (assuming typical pro-touring roll angles and suspension travel). Compared to tire and bushing deflection, that's negligible in my opinion. Here's a fairly balanced article on the subject: https://www.maximummotorsports.com/Busting-the-Myth-of-the-Watts-Link.aspx

[dontlifttoshift]

On a street car I don't think the RideTech four link for the 2nd gen F bodies needs the sway bar. It is very small in diameter and I run mine on the softest setting........even with a very large bar in the front.

The watts vs PHB debate will rage on forever......Just like every A vs B discussion where both A and B do the job effectively with minor differences between the two that have little effect on 99% of the applications.

Watts is easier to get the roll center low enough. PHB is easier to package and has less moving parts.

[Rsj4h]

On a street car I don't think the RideTech four link for the 2nd gen F bodies needs the sway bar. It is very small in diameter and I run mine on the softest setting........even with a very large bar in the front.

The watts vs PHB debate will rage on forever......Just like every A vs B discussion where both A and B do the job effectively with minor differences between the two that have little effect on 99% of the applications.

Watts is easier to get the roll center low enough. PHB is easier to package and has less moving parts. Any difference in how the RT triangulated links affect ride/handling versus PHB? How do you like the ride of your four link? A lot of people say it’s night and day, but don’t really describe the ride quality and seem to comment more on the improved handling. I usually see the same comments with Torque arms.


Hard to say if you'd need to run a rear sway bar with the Ridetech system... depends on a ton of variables like spring rates, front sway bar rate, roll center heights, weight distribution, tire stagger, etc. If you shared details about your car, some people with similar setups might chime in. Or better yet, call Ridetech and ask them directly.


I think Watt's links are cool, but in the real world I can't imagine anyone could feel the roughly 1/16" of lateral movement caused by a panhard bar (assuming typical pro-touring roll angles and suspension travel). Compared to tire and bushing deflection, that's negligible in my opinion. Here's a fairly balanced article on the subject: https://www.maximummotorsports.com/Busting-the-Myth-of-the-Watts-Link.aspx I figure I will try it without first to see if there were any need. The front will have the Ridetech TruTurn coilover system and Musclebar.


Watts Link all day long

https://static1.pt-content.com/images/pt/2021/05/differencespanhardbarwattslink2018122322-1.gif (https://postimages.org/) Do you have any comments with comparisons of ride and handling with the torque arm versus a triangulated four link?

[dontlifttoshift]

Ride quality is quite good, even with the R joints and bearing mounted shocks but I am leaving quite a bit on the table with 300# springs in the rear.......it's a compromise I am willing to make. If you are not tubbing the car, I strongly recommend leaving the factory bump stops in place.

When I had S197 Mustangs, all the hard parker, track day hero guys raved about how much better the car rode after converting from a PHB to a Watts......... I was skeptical and remain so to this day, but admittedly have no science or personal experience regarding the watts. As stated above, to many moving parts and packaging issues for me to actively choose the watts over a PHB.

[BMR Sales]

Do you have any comments with comparisons of ride and handling with the torque arm versus a triangulated four link?

Plenty, my early post was trying to show the simplicity of a Watts Link

Nothing wrong with a 4 Link, heck that system works well in a Lot of cars. However to put a 4 Link into a car that we are referring to takes a bunch of fabrication ( and you better hope that your calculations are correct).

A Torque Arm w/ Watts Link is a Kit that goes a step further, stops all unwanted movement while allowing full articulation. Effective and No Fabrication Needed

[Rsj4h]

Ride quality is quite good, even with the R joints and bearing mounted shocks but I am leaving quite a bit on the table with 300# springs in the rear.......it's a compromise I am willing to make. If you are not tubbing the car, I strongly recommend leaving the factory bump stops in place.

When I had S197 Mustangs, all the hard parker, track day hero guys raved about how much better the car rode after converting from a PHB to a Watts......... I was skeptical and remain so to this day, but admittedly have no science or personal experience regarding the watts. As stated above, to many moving parts and packaging issues for me to actively choose the watts over a PHB.
So do the R-Joints provide a somewhat harsher ride due to the fact they have no give and would that give an advantage to the torque arm? Josh with Ridetech has told me that 225# springs would be good in my application. Chadwick with Speedtech recommended the same rate with their torque arm system.

[dontlifttoshift]

There are two components to ride quality.......at least this is my take on it.

First is actual ride quality. The ability of the tires to follow and absorb bumps in the road without upsetting the car and consequently the driver. The problem is roads are drastically different everywhere and so are speeds. So spring rate requirements are different, that's why rubber or foam bumpstops are so important on a street car, you can run less spring without bottoming out. That's why it is also nice to have the ridetech triple adjustable shocks or similar, you can put more high speed compression in to slow down the spring action in big bumps so the car doesn't bottom out while leaving the low speed soft.

The other side of it is NVH, noise, vibration, harshness. This is typically what people mean when complaining about ride quality. If the car squeaks, rattles, thumps, etc over bumps, it is perceived as bad ride quality.

I'll use my heap as an example. It was built 50 years ago, I have never had the interior out or any of the sheetmetal off, just dropped the subframe to do the engine and suspension swap and put it back together with solid subframe mounts. The car has the whole ridetech catalog in it. Before that I drove it around stock and didn't really have many squeaks or rattles.

It does now. Every bump is transferred directly into the unibody and the whole car is made of squeaks and rattles. But that's not a suspension problem, that's a car problem. Actual ride quality is on par with the 2018 1LE I had, maybe 20% harsher. Again that is a function of spring rates and also the IRS in the rear of the late model. The difference in NVH between the two cars is enormous. That's a function of giant rubber bushings and hundreds of other engineering marvels to isolate the driver from road irregularities and the sounds and feels they make.

So the short answer is that R joints, sphericals, or even delrin bushings don't make for a harsher ride. They just do not allow the bump energy to dissipate. Consequently that bump energy transfers from your tire to that dash screw that isn't quite all the way tight unimpeded.

[TanMan]

Watts Link all day long

https://static1.pt-content.com/images/pt/2021/05/differencespanhardbarwattslink2018122322-1.gif (https://postimages.org/)

Best demonstration of a Watt’s link that I’ve ever seen.

[cpd004]

For what it's worth, I have 225lb in the rear in my '71 Firebird. I have the older design 4 link and just recently added the R Joint links. I started out with 275lb based on someone other than RT's suggestion and though it was too harsh. I went down to 250 worrying about the 50lb drop being too much and the ride was much better-speaking strictly street car at the moment. Much better, but still thought they were a touch much. Finally down to 225 and these seem right on ride wise. I no longer the pop pop pop going over cracks in the roadway. This is what worked on my car with 275/40/18 sized tire. Taller than most probably run. An expensive journey to get to the right rates back and front. This reminds me-I need to update a for sale post!