Torque Arm for drag racing...Ron?

[andrewb70]

I am in the process of building a 1967 Cougar that is destined for mostly street and the occasional use on the strip. This isn't going to be a car that will be used for auto-cross or road racing.

Right now the car has leaf springs and some old Ansen "ground grabber" traction bars. These are similar to modern Caltracks, but not exactly the same. I have been thinning about adding a torque arm to the rear suspension in place of the Ansen traction bars to maximize anti-squat. I know squat about analyzing suspension components, which is why I am asking the folks here to chime in.

Total Control Products offer a 36" long torque arm for the early Cougars:

http://www.totalcontrolproducts.com/torquearm.html

The plan would be to use the torque arm with the leaf springs to control spring wrap and help with forward traction. Can someone that knows this stuff tell me if this will be good, bad, or indifferent for my goals? :hammer:

Andrew

[72BBSwinger]

Have you looked at Assassin bars?
http://www.smithracecraft.com/index.php?page=shop.product_details&category_id=28&flypage=flypage.tpl&product_id=50&option=com_virtuemart&Itemid=1
The torque arm wouldn't allow a lot of adjustability I wouldn't think.

[shmoov69]

I'm curious to hear because I'm not sure if it's work or not with the different pivot points. But then again, the TQ arm we built for the Camaro uses coilovers which is a different point. But at least it's above the other end of the TQ arm. Don't know if it matters at all or not. Curious.

[72BBSwinger]

That TCP torque arm is a nice design in that it incorporates a dogbone in the front pivot so it allows the axle to still move for and aft. I like it, nice find Andrew.

[bergers59]

I would think a set of single leafs and caltracs would be the way to go. Guys run down to the 8's with those

[andrewb70]

I would think a set of single leafs and caltracs would be the way to go. Guys run down to the 8's with those

I am sure that is probably the way to go, but I like to be different (read...stupid...LOL)

Andrew

[andrewb70]

Have you looked at Assassin bars?
http://www.smithracecraft.com/index.php?page=shop.product_details&category_id=28&flypage=flypage.tpl&product_id=50&option=com_virtuemart&Itemid=1
The torque arm wouldn't allow a lot of adjustability I wouldn't think.

Don't make them for a Cougar...

Calvert racing does make Caltraks for a Cougar, but I am trying to avoid having those bars hanging down below the spring. The torque arm is stealthy...Cause you know, a tunnel ram and a Bug Catcher are so subtle...

Andrew

[bryant]

the torque arm will want the twist the axle housing in a arc around the front pivot point. leaf springs dont move the diff in an arc at all. so this will create a bind and or spring wrap in the spring when the suspension travels up and down. spring wrap will cause loss of traction quickly. using a torque arm on leaf springs is very similar to using ladder bars with leafs. you need to use leaf spring floaters to allow the diff to move in and arc of the torque arm or ladder bar and for the leaf spring to not be forced into a bind or spring wrap.

[andrewb70]

the torque arm will want the twist the axle housing in a arc around the front pivot point. leaf springs dont move the diff in an arc at all. so this will create a bind and or spring wrap in the spring when the suspension travels up and down. spring wrap will cause loss of traction quickly. using a torque arm on leaf springs is very similar to using ladder bars with leafs. you need to use leaf spring floaters to allow the diff to move in and arc of the torque arm or ladder bar and for the leaf spring to not be forced into a bind or spring wrap.

I read all that as "unless you do some other stuff this will suck." Is that about right?

Andrew

[TLWiltman]

Yes. That is indeed what I'm catching out of that. Basically, the leaf springs and a torque arm have different motion arcs that will conflict. You'll have to resolve those conflicts with other equipment.

[wendell]

the torque arm will want the twist the axle housing in a arc around the front pivot point. leaf springs dont move the diff in an arc at all. so this will create a bind and or spring wrap in the spring when the suspension travels up and down. spring wrap will cause loss of traction quickly. using a torque arm on leaf springs is very similar to using ladder bars with leafs. you need to use leaf spring floaters to allow the diff to move in and arc of the torque arm or ladder bar and for the leaf spring to not be forced into a bind or spring wrap.

Are you talking in side view? Because in side view the front pivot of a torque arm is telescopic or a dog bone letting the control arms (or leafs in this case) define axle travel. Unlike ladder bars.

If I wanted to hook on leafs with out caltracks, I would punch a hole in the trunk pan and run a third link rubber bumpers in compression. I've seen it worth more than a second on a slow one minute road track (no idea how that translates to a 1/4 mile).

[bryant]

yes side view. even with the front mount being able to move forward and back, the arm will be pulling down on the pinion when the diff goes up and up on the pinion when the diff goes down. this will wrap up the springs.
if you were to put a torque arm on the diff and leave the front of it detached then lift the car off the ground, the front of the torque arm will move down with the rear end. to push the torque arm up to where it can be attached will wrap up the springs.
now add a floater kit like this
109627

or this

109628

and the spring will be able to work as intended.

[72BBSwinger]

Leaf springs move in an arc also when they have little to no arch. This torque arm is 36" which actually creates less of an arc than the leafs would. If a guy is trying to use this setup with a bunch of travel it would then raise its ugly head, but not in a track car that MIGHT see 5" of travel. I still wouldn't use this in a strip car, I'd just use Mopar SS leaves.

[wendell]

scrap it

[andrewb70]

scrap it

Scrap what?

[killer69]

the torque arm will want the twist the axle housing in a arc around the front pivot point. leaf springs dont move the diff in an arc at all. so this will create a bind and or spring wrap in the spring when the suspension travels up and down. spring wrap will cause loss of traction quickly. using a torque arm on leaf springs is very similar to using ladder bars with leafs. you need to use leaf spring floaters to allow the diff to move in and arc of the torque arm or ladder bar and for the leaf spring to not be forced into a bind or spring wrap.

Not Really. but sort of. if you were to look at our TA if instance the front mount slides inside a tube and can rotate as well as move up and down. so even if attached to a rear end that is mounted on leaf springs even though there are 2 different pivot locations because the front of the TA is not rigidly mounted it will not cause bind in the suspension, it WILL stop any axle rotation. it would be an interesting combo to try. some of the 4th gen stock eliminator Camaros work pretty good with a TA in them.

[Nothingface5384]

Heres a clipping from Rons thread over at Lateral G , that i just came across today due to a similar question i had.

For drag racing, the advantage goes to the Parallel 4-link, with the Torque Arm suspension 2nd (for handling launches BUT not very adjustable), Triangulated 4-link 3rd & the 3-link 4th (only due to strength concerns).

http://www.lateral-g.net/forums/showthread.php4?t=42568

[andrewb70]

Sounds like the most practical solution at this point is to see how those vintage Ansen Ground Grabbers work, and take it from there. The car is not super powerful, so hopefully it'll hook with some drag radials.

Andrew

[wendell]

Scrap what?

I couldn't figure out how to delete my post. I think what Bryant is saying is that the because the leafs are rigid mounted to the axle, it will be less effective at transferring weight to the TA. Which is accurate.

[Carl @ Chassisworks]

Andrew,
I'm going to put together a little bit of info for you when I get a chance this afternoon but I have a few questions first.

How much horsepower, give or take 50, is your Cougar going to have?
What tire compound and sizes will it have at the drag strip?
What transmission will the car have?
Are you looking at the TCP torque arm because it's a simple solution, or are you looking for the best solution without cutting up the car?

~Carl

[andrewb70]

Andrew,
I'm going to put together a little bit of info for you when I get a chance this afternoon but I have a few questions first.

How much horsepower, give or take 50, is your Cougar going to have?
What tire compound and sizes will it have at the drag strip?
What transmission will the car have?
Are you looking at the TCP torque arm because it's a simple solution, or are you looking for the best solution without cutting up the car?

~Carl

Carl,

Thanks for jumping in here. I am sure there are others that would love to know more about this product.

Horsepower will be 450 flywheel max.
Current plan is to run 255/60-15 Mickey Thompson drag radials
T56 trans, 9" rear with detroit locker and 4.30 gears

I am looking at the TCP torque arm because it is potentially a better solution than Caltraks. By "better" I mean more suited for street and strip. My goal is to have a car that hooks well on a prepped track. I'd like to pull at least 1.5x 60 foot times and still retain good street manners. I also like the whole under brace deal that also functions as the anchor point for the torque arm.

Andrew

[Ron Sutton]

Sorry I'm late to the party Andrew. I was at Thunderhill for 4 days.

I never ran leaf springs on my personal drag cars. I did with clients cars, but because a good 4-link kit can be had for $450 with rod ends & a diagonal link for under $100 ... I always went the 4-link route. The 4-link has several advantages over a leaf spring strategy, and the cost is not much more unless you make it by buying high end coil overs.
Links:
https://www.cachassisworks.com/c-421-battle-cruiser-4-link.aspx
https://www.cachassisworks.com/p-287-locater-for-4-link-34-clevis-bolt-on.aspx

Traction bars & Cal-trac bars are going to use the front pivot of the leaf spring as the instant center. You can fabricate mounts to move this pivot up or down to change the instant center (and anti-squat) but that's a lot of work for very little change. The torque arm mentioned will NOT cause bind with the leaf spring, because it's on a pivot strap. Just like Blake mentioned ... theirs is on a slide ... so the torque & leafs can have a different arc & not bind. So that's really a non-issue. With the torque arm, you're moving the pick up point, instant center & anti-squat from the leaf spring. Where you place it would be the determining factor as to whether the new location was better or not.

Back to the 4-link ... but first let's discuss shocks for a minute ... then take shocks out of the equation. With any competition or performance car, you want to buy the best shocks your budget can tolerate, because they are such a key factor to the performance. If you're running leaf springs ... your racing shock choices range from under a $100 to infinity. Let's say you budget $175 for a smooth body (non-coil-over) single adjustable (gas) mono-shock ... times two for the rear. If your leafs are the right rate ... you have $350 in shocks & springs. If your leaf spring rate is not good for your purpose, you can pick up used springs for $100 to new springs for $300. now we're $450-$650 in springs & shocks. There are several equal quality, single adjustable gas coil-over shocks that can be had for $450-600 ... with whatever spring rate is optimum.

My two key points here are:
1. Get the best shock you can afford.
2. If we care to get the optimum spring rate, the cost of leafs & shocks isn't much different than coil overs ... as long as we're comparing apples to apples in shock quality.

So ... if we take spring rate & shock quality out of the equation, then we're comparing a leaf spring "add-on" like a torque arm, traction bar or Cal-tracs. Pretty easy to spend $340-400+ on these options. A good 4-link with a diagonal link is a little over $500. Add a crossmember (which helps stiffen the chassis) & some shock mounts ... and now you're still under $700. The cost is pretty close, but the performance & tunability is much better with the 4-link.

The 4-link coil-over advantages are:
#1 - You can shift a higher percentage of the rear housing rotational torque to lifting the chassis & loading the rear tires, providing significantly increased traction & quicker ETs.
#2 - You can adjust the instant center & anti-squat to be optimum for your car ... your combination of engine, trans, clutch/converter, trans brake (or not) your choice of tire, etc.
#3 - If you make changes to improve the car down the road, you can simply adjust the 4-link instant center & anti-squat to be optimum for your new set-up
#4 - You can tune the suspension around the car & the track, versus tuning everything else to tune around the leaf spring.
#5 - It's probably lighter (especially if you were thinking multi-leafs)
#6 - You can adjust corner weights easily to neutralize/minimize initial launch torque steer
#7 - You can change the ride height of the car quick & easily
#8 - It increases the value of your car at resale
#9 - Coil over spring rate changes cost a fraction compared to leaf spring rates.
#10 - You can use a smidge of pre-load if needed to ensure the car launches straight
#11 - Less harmonics issues going away from leaf springs to coil overs
#12 - Asking a "spring" to do three jobs: lateral locator, suspension leverage/linkage & act as a spring is taxing on the spring. Where in a 4-link, the diagonal link is the lateral locator, the 4 links are the suspension leverage/linkage devices & the coil spring only acts as a spring.

Anyway, back at the ranch, before someone flames this post and mentions how fast drag cars can be with leaf springs ... I get it ... any suspension can be made to work. And after enough development, you can make them achieve impressive things. But a coil-over 4-link set-up is an easier, better way to do it ... and not cost much more. In the end, it's your car and it's about what you WANT to do.

Best wishes Andrew !

[Carl @ Chassisworks]

Carl,
Thanks for jumping in here. I am sure there are others that would love to know more about this product.


Andrew,
Obviously a drag-race style 4-link would be ideal but since Ron covered that so well, I will respond directly to the torque arm question.

Based on the power level that you have in the car the TCP Torque Arm would be a good option for your street/strip car. The arm itself is extremely strong with mandrel-bent tubes and billet steel CNC machined connecting points. I won’t bore you with endless details but you can read them all here: http://www.totalcontrolproducts.com/download/datasheets/TA2F9-33_DS_WEB.pdf

Everything will go right together with our g-Connector kit. They fit the floor really well. Plus, when you order the package it includes a bolt-in driveshaft loop. To give you an idea of how much detail there is in even the little pieces, the loop isn’t just some pipe from the hardware store. It’s 5-1/2” ID DOM tubing which has been CNC cut, deburred in a CNC lathe, fixture welded, then powder coated. More tech can be found on the connector system here: http://www.totalcontrolproducts.com/download/datasheets/SUB_DS_WEB.pdf

The fact that you are running a slick and a stickshift means that it will see some pretty aggressive launches. 1.5s should be possible. I strongly encourage you to make sure you add “Inspect COM bearings in T/A dogbone” to your standard maintenance list. To get the car to launch hard, you’re going to need a softer spring, possibly remove two leafs. This is true for CalTracs style cars, too. It should be noted that the CalTracs wear out the leaf in two seasons, less if you race a lot. It’s a consumable, just like tires. The important part of the equation is going to be the shocks. They’re the brains of the operation, everything else is the working man. We are getting great feedback on the new VariShock SS bolt-ins (http://www.cachassisworks.com/c-264-bolt-in-oem-replacement.aspx), but I would suggest stepping up to at least a single adjustable shock. Double adjustable would be worth the extra couple bucks if you are going to take the drag radials off and run it around town a bit, too.

About Torque Arm Suspensions:
To my knowledge, there is not a torque arm configuration that requires a housing/leaf spring floater. However, all torque arms have one ‘floating’ connection point to prevent bind. The 3rd and 4th –gen Camaro had torque arms with a steel slider in a rubber bushing. Our drag race torque arm for the same car has a trick steel-on-steel slider for more precision. The TCP torque arm has a “Dogbone” connector with COM bearings.

Thinking about the arm and leaf spring travelling in different arcs is misleading. All link-type suspensions have parts that travel in different arcs. Think of the front half of the leaf spring as a control arm that happens to flex a bit. Think of the back half of it as a lateral locating device (Panhard/Watts/Satchel/Track Locater) Once you do that, the system isn’t much different than many others except it is easier to work with.

To calculate the instant center of a torque arm suspension you draw a vertical line through the torque arm front mount. Then you draw a line from the center of the tire contact patch through the lower control arm pivot. In this example, we would call that the front leaf spring eye. The instant center is the point where the two lines intersect.


The TCP arm was initially developed as part of the TCP RPSS rear Pushrod suspension system; the same suspension that is in the dominant TCP Racing Fastback (https://www.facebook.com/media/set/?set=a.390020951103001.1073741831.301204599984637&type=3). We don’t own the car anymore, Kevin Sittner took over as chief competitor/new parts thrasher several years ago, but we do have visitation rights.

Speaking of Kevin, the red ’67 below is a real GT350 that he also owns. It has leaf springs, VariShock bolt-in shocks, TCP subframe connectors, and the TCP Torque Arm. Up front it has our rack and pinion steering and VariShock coilover kit.

https://static1.pt-content.com/images/noimg.gif

[Vegas 69]

Hey Ron

Great write up.

I like the Torque Arm set up with Coil Overs. You get all the advantage of a 4 link and IMHO you will have a better street ride. TA does not cost much more then 4 link

[andrewb70]

Carl,

Thanks for the thoughtful write-up. It definitely gives me some things to think about. Perhaps the thing to do in the short term is get the car running, as is, then start to fiddle with other parts if what I have is not satisfactory.

Andrew

[Carl @ Chassisworks]

Another note about Cal-Tracs. They are a great product for the money, and the Calverts are great people. That said, just because there are racers who can go 8s on them doesn't mean they are ideal. A large part of that ET is modern engine management software. They're fairly noisy on the street and ride quality isn't improved. If I was throwing together a budget drag car I would just stick some ladder bars in it and deal with the bumpy ride. That's my personal 2-cents.


Carl,

Thanks for the thoughtful write-up. It definitely gives me some things to think about. Perhaps the thing to do in the short term is get the car running, as is, then start to fiddle with other parts if what I have is not satisfactory.

Andrew

Thoughtful write-ups to solid information is how I get through the Monday blues. I should be thanking you for answering my questions and not providing ten pages of useless information. ...because that NEVER happens in my work inbox... :D

[shmoov69]

Andrew, I think with the power that you will be making, that what you had Will work just fine with good shocks and pinion angle adjustments.
And for the record my TQ arm has a slider style front mount with a big diameter sway bar mount. Seems to be working fine with coil overs.

[Ron Sutton]

Hey Ron

Great write up.

I like the Torque Arm set up with Coil Overs. You get all the advantage of a 4 link and IMHO you will have a better street ride. TA does not cost much more then 4 link

Hi Todd!

I also like the Torque arm. it is much better for street, track, protouring & autocross. But for a drag car, the 4-link has some advantages.

:cheers:

[Ron Sutton]

Andrew,
Obviously a drag-race style 4-link would be ideal but since Ron covered that so well, I will respond directly to the torque arm question.

Based on the power level that you have in the car the TCP Torque Arm would be a good option for your street/strip car. The arm itself is extremely strong with mandrel-bent tubes and billet steel CNC machined connecting points. I won’t bore you with endless details but you can read them all here: http://www.totalcontrolproducts.com/download/datasheets/TA2F9-33_DS_WEB.pdf

Everything will go right together with our g-Connector kit. They fit the floor really well. Plus, when you order the package it includes a bolt-in driveshaft loop. To give you an idea of how much detail there is in even the little pieces, the loop isn’t just some pipe from the hardware store. It’s 5-1/2” ID DOM tubing which has been CNC cut, deburred in a CNC lathe, fixture welded, then powder coated. More tech can be found on the connector system here: http://www.totalcontrolproducts.com/download/datasheets/SUB_DS_WEB.pdf

The fact that you are running a slick and a stickshift means that it will see some pretty aggressive launches. 1.5s should be possible. I strongly encourage you to make sure you add “Inspect COM bearings in T/A dogbone” to your standard maintenance list. To get the car to launch hard, you’re going to need a softer spring, possibly remove two leafs. This is true for CalTracs style cars, too. It should be noted that the CalTracs wear out the leaf in two seasons, less if you race a lot. It’s a consumable, just like tires. The important part of the equation is going to be the shocks. They’re the brains of the operation, everything else is the working man. We are getting great feedback on the new VariShock SS bolt-ins (http://www.cachassisworks.com/c-264-bolt-in-oem-replacement.aspx), but I would suggest stepping up to at least a single adjustable shock. Double adjustable would be worth the extra couple bucks if you are going to take the drag radials off and run it around town a bit, too.

About Torque Arm Suspensions:
To my knowledge, there is not a torque arm configuration that requires a housing/leaf spring floater. However, all torque arms have one ‘floating’ connection point to prevent bind. The 3rd and 4th –gen Camaro had torque arms with a steel slider in a rubber bushing. Our drag race torque arm for the same car has a trick steel-on-steel slider for more precision. The TCP torque arm has a “Dogbone” connector with COM bearings.

Thinking about the arm and leaf spring travelling in different arcs is misleading. All link-type suspensions have parts that travel in different arcs. Think of the front half of the leaf spring as a control arm that happens to flex a bit. Think of the back half of it as a lateral locating device (Panhard/Watts/Satchel/Track Locater) Once you do that, the system isn’t much different than many others except it is easier to work with.

To calculate the instant center of a torque arm suspension you draw a vertical line through the torque arm front mount. Then you draw a line from the center of the tire contact patch through the lower control arm pivot. In this example, we would call that the front leaf spring eye. The instant center is the point where the two lines intersect.


The TCP arm was initially developed as part of the TCP RPSS rear Pushrod suspension system; the same suspension that is in the dominant TCP Racing Fastback (https://www.facebook.com/media/set/?set=a.390020951103001.1073741831.301204599984637&type=3). We don’t own the car anymore, Kevin Sittner took over as chief competitor/new parts thrasher several years ago, but we do have visitation rights.

Speaking of Kevin, the red ’67 below is a real GT350 that he also owns. It has leaf springs, VariShock bolt-in shocks, TCP subframe connectors, and the TCP Torque Arm. Up front it has our rack and pinion steering and VariShock coilover kit.

https://static1.pt-content.com/images/noimg.gif

Nice write up Carl!

[killer69]

Hi Todd!

I also like the Torque arm. it is much better for street, track, protouring & autocross. But for a drag car, the 4-link has some advantages.

:cheers:



Given the option I too would choose a 4 like for ANY SERIOUS DRAG ONLY CAR. for a combo street/drag car ???? I don't think a drag race 4 link is the way to go on the street
Currently in the shop we have a 64 Elcamino that we back 1/2ed, since the triangulated 4 link was not going to work with the narrowed rear end we built a frame and had some front and rear end brackets cut to run a short upper/long lower arm parallel 4 link with a panhard bar( yes a diagonal link would have been better for strictly drag race but I think a panhard is stronger on the street) we used our standard Delrin bushings and Articulink joints to make it more streetable as far as noise and longevity go. I can post some pics next week once the frame and rear end get back from powder coat.