Alcino's MII suspension uncovered

[alcino]

Ever since the article in PHR about my car, I get a lot a questions on my suspension and how I pulled .99g and 5.95sec slalom. It’s amazing handling in the tests shocked many people, including me. I've read a few books on suspension and knew I was a long shot at doing well in handling. For one its a Mustang II suspension, known for its bad geometry caused by its short and misplaced control arms and two I had lowered the car so far down(mostly for looks) that I had broken the cardinal rule of having the lower control arm not angling down from the chassis to the spindle. So I decided look into it more and write about the details.

Facts about the suspension.
1. Completely factory stock suspension parts except poly bushings.
2. Alignment. -2* camber, 3*caster, 0.25" toe out.
3. Front inner lower control arm pivot height from ground = ~6 3/8"
4. Lower balljoint from ground height = ~7"
5. Track width from center of tread to center of chassis = ~29 3/4"
6. Tires in front are 205/50/15 and rear 225/50/15 Toyo RA-1

Using Suspension analyzer and its included 78 mustang ii file set to height, tire and alignment parameters of my car to test the Roll Center(RC) height at rest and migration with 2* roll, .5* steering input(left turn) and .25 dive/bump(lets call all this "dynamic").

At rest RC is 0.11" above ground. I think this is really low. Care to comment?

Now the interesting part. Dynamic. As I start adding the steer the RC moves 4.17" Passenger side from center(call this "P"), then as I add the roll it moves the other way and ends up 6.94" Drivers side from center(lets call "D"), then as crazy as it seems as I add the bump some where around .13" it goes as far as ~144" D then ~104" P and as I get to .25 bump RC ends up at 2.71 P. Note height of CR doesn't seem to change much other that following the chassis. So it ended up -.14".

Seeing this happen in animation is wild to say the least. But explains Why my car feels hairy when I let off or touch my brakes in a fast turn. A condition that is not tested and means a great deal in the real world race situations.

So knowing the problem. What are some solutions? I tested a few ideas that are mentioned all the time.

Such as using common 2" drop spindles and restoring ride height. This corrected the Lower control arm angle and put static RC ht at 2.93". Adding the steer caused no movement of RC, adding roll slowly moved RC 4.37" D, lastly adding the dive only pulled the RC slightly leaving it at 4.97" D and 2.47" off ground.

Another trick is longer control arms and shallow dish wheels. I made my arm 3" longer. Static RC ht. 2.6". Adding steer = nothing, adding roll = 3.78" to D, adding the bump pulls it to 4.37" D from center with 2.20" from ground.

For comparison Suspension Analyzer has a 2001 corvette. Static RC ht. = 2.92". Dynamically the RC barely moves and ends up at 0.73" D from center and 2.62" from the ground. must feel very predictable.

Playing with the MII suspension even more found me some places that help it act more like a c5. Such as a taller spindle which is available from chassis works (and maybe ATS in future). Also moving the upper control arm inner pivots down. Just to see I used the last MII scenario moved the upper ball joints 1.5" to simulate the tall chassis works spindle and moved the upper inner a-arm points down an inch. Static RC ht. = 5.59". Dynamic RC = 1.57" D and 5.23" from ground. Is that a High RC? Closer to c5 RC migration, right. But could you still call it an MII suspension?

Conclusion. My tires are great and… I need some freaking drop spindles stat:eek:!

Hope someone enjoys my work here.

[bret]

Congrats, first, on taking a less than optimum suspension [on paper]and wringing out impressive performance, and second, for documenting why. Thanks for taking the time to explore this issue. One [many?] would think that being a proponent of the MII front suspension that I would have have this info at my fingertips...but I don't. My real world experience with this suspension has been subjectively similar, although not documented and likely not quite as successful as yours. Even though there are dynos, races continue to be run...even though therory says this suspension should not work this well, it apparantly does in this case.
Congrats as well on continuing to try to improve your hotrod...it is why the free world still goes to work every morning!

[BRIAN]

Probably the BEST suspension post on this site. You took a less than optimal suspension, didn't buy the "Must Have" parts and made them perform very well.


That is exactly what should be done. It would allow a lot of younger people with low funds enjoy their PT cars rather than buy the big buck piece of the week. You are the Rat Rod of Pro Touring and I do not mean that as an insult.


One question; Did you ever perform the test with a different tire just to see how much they effect the G's??

[alcino]

Probably the BEST suspension post on this site. You took a less than optimal suspension, didn't buy the "Must Have" parts and made them perform very well.

That is exactly what should be done. It would allow a lot of younger people with low funds enjoy their PT cars rather than buy the big buck piece of the week. You are the Rat Rod of Pro Touring and I do not mean that as an insult.
Thanks.


One question; Did you ever perform the test with a different tire just to see how much they effect the G's??
No, and probably never will. I was lucky that I was able to have this data collected. Lots of people wonder what their car could do, but don't have the resources to do it. That's me no resources. No extra wheels/tires, no fancy timing lights. I might be wrong, but didn't PHR do a write up on tires a few months ago? I think it was all Nitto brand, but might have had some numbers comparing the different compounds.

[Stu Seitz]

That’s awesome, but if your springs are stock and you’re pulling .99 g’s how are you not hitting the suspension stops? I would assume that, in it of it self would some what hinder performance at the limit. And if your shocks are stock and you’re already at .99 g’s I think that a good set of Koni’s or Penske’s would go a long way and wouldn’t break the bank. Once again man awesome post; I really like what you’re doing with your car.

[alcino]

And if you shocks are stock

Ooops, forgot to mention that I have KYB Gas Adjusts in the front and KYB GR2 in the rear. And they don't seem to be binding. Maybe next time at AutoX or something I will put a zip tie on the shock shaft and see how close it gets to bottoming.

[red65FB]

alcino-

Great post! I used to have a C5 - and your assumption is correct - very stable and predictable.

I have some old software I can use to solid model some arms, and I might be able to get some fabbed. I wonder if the Chassisworks spindles are a direct bolt in - brake mounts, axle snout, ball joint taper, etc., are the same as stock?

[JJSmitches]

There is a 1976 Mustang Cobra in the SF Craigslist for 1k. GO GO GO!

[alcino]

Here is the Chassis Works spindle next to the stock. Axle snout is the same. Not sure if the Balljoint taper is stock or Chrysler. But the most irratating thing is that they limit you to a 11.75" rotor with their cast in caliper bracket. ATS, please rescue us!
https://static1.pt-content.com/images/noimg.gif

[CAMAROBOY69]

The fact that you were also running 15" wheels and tires amazes me. Do you think you would do even better with 16" or 17" wheels. I know my car cornered a lot better with 18" than it did with 14" or 15".

[Norm Peterson]

Hope someone enjoys my work here.Very much. Do you happen to have the coordinates of the upper pivots and balljoint handy?

Wild lateral migration of the geometric RC occur as the upper and lower arms pass through being parallel to one another. I see the same effect in a 2-D spreadsheet with an animated plot. The shorter uppers rotate as seen in front view faster than do the longer lowers in roughly inverse proportion to the relative arm lengths.

Norm

[kmcanally]

The fact that you were also running 15" wheels and tires amazes me. Do you think you would do even better with 16" or 17" wheels. I know my car cornered a lot better with 18" than it did with 14" or 15".

Jay Bittle's Trans Am Mustang pulled 1.01g with a modified stock suspension on period correct vintage 15" bias ply race rubber.

[David Pozzi]

Al,
Try the LCA frame pivot 1" higher than the lower balljoint at starting ride height.
Use the taller drop spindle, how much taller is it?
Then play with UCA inner pivot heights to get some neg camber gain.

The Mustang II has some advantages especially in a slalom.
Shorter wheelbase requires less wheel turn to get around the cones, less work for the front tires.
The inside rear wheel is what will hit a cone on a turn, a shorter wheelbase has less difference in path betweeen the front and rear wheels.
Car width is less, the car takes a straighter line through the cones, less degrees of turn per cone.

[red65FB]

ok - I quickly threw together a model based on a Heidts style tubular control arm using 1" tubing. This is very quick - only for visualization. Please note this is only with quick measuring crawling under the car. But, it does give you a good idea of what an extended length (added 3") LCA might look like using the stock MII crossmember. This assumes staying with the stock spring perch type and upper pocket set up - no coil overs. One thing that immediately pops out is the increased leverage on the spring.

For the experienced among us - can I assume that the spring would need an increase in rate? If so, how much?

[David Pozzi]

"can I assume that the spring would need an increase in rate? If so, how much?"

No it will get stiffer, the spring will now be closer to the balljoint percentage wise if the arm is lengthened inboard of the shock.
Hope the spring and shock angles won't cause problems. I assume the shock is inside the spring?

[alcino]

Do you happen to have the coordinates of the upper pivots and balljoint handy?

Wild lateral migration of the geometric RC occur as the upper and lower arms pass through being parallel to one another.

Yes! That's what what must be happening. The arms are near parallel at rest. forgot about that in my suspension books.


Do you think you would do even better with 16" or 17" wheels. Not sure? I feel it doesn't matter much on wheel. Just profile and compound of rubber.

David, I will play some more with the analyzer to see what happens. When is the RC considered too high?


For the experienced among us - can I assume that the spring would need an increase in rate? If so, how much?
I think if the wheel doesn't move outboard with the arms that the spring rate could stay the same. Correct me if I'm wrong.

[Norm Peterson]

ok - I quickly threw together a model based on a Heidts style tubular control arm using 1" tubing. This is very quick - only for visualization. Please note this is only with quick measuring crawling under the car. But, it does give you a good idea of what an extended length (added 3") LCA might look like using the stock MII crossmember. This assumes staying with the stock spring perch type and upper pocket set up - no coil overs. One thing that immediately pops out is the increased leverage on the spring.

For the experienced among us - can I assume that the spring would need an increase in rate? If so, how much?If all of the length increase is added between the spring seat and the balljoint, then yes, you will want more spring rate (in the ratio of [motion ratio]^2).

If it's all added between the spring seat and the chassis pivot, less spring. How much less would also depend on how much the spring angle changed.

Norm

[hssss]

FWIW. Could you use the spindles off either a Granada or Torino? I believe both were front steer and should be taller. I believe the granada and MII both grew out of the same parent, the Falcon. The box style Towncar came factory with tubular UCAs and the spindles look like Torino. I have found that engineers don't reinvent anything they don't have to so possibly a set of spindles off a larger car with the CAs adjusted to accomodate them might be the answer. Being Frugal/cheap whenever possible I like to use production parts which are generaly also stronger. Just ran accross this they will make the spindle effectivly a bit taller http://www.scandc.com/balljoints.htm

[alcino]

hsss, thanks for letting me know about the balljoints.

I called Chassisworks about their spindle. The first thing they said was that it would not work on my car. Only on their suspension kit. Ya right! I asked some more questions, but the guy didn't really know what he was talking about.

I ordered them to see what they were and make comparisons. I will make a better write up, but on the quick glance over.

1. The snouts are the same as the stock II using the same bearings with only the nut being a different thread pitch.
2. The upper Ball joint is moved 1 1/16" higher than stock.
3. These babies are heavy duty and you can feel it in the weight. stock is just over 8 lbs. while these come in at 12.5 lbs. I'm thinking I could grind some material away since my car is light.
4. the snout is moved up 2" giving it that amount of chassis drop.
5. Seems to accept the same style balljoints and tierods.

I tried a factory 9" rotor and it would hit the bracket for the caliper. Maybe I could get some time this week and see how my wilwood rotors fit.

[hssss]

alcino What if you used something like the 95 Cobra R wheel 17x9x5.95(offset) this would allow lengthening the lca and still maintaining the track width? I just got 17x10.5x6.9 for the LC7. If you have any thoughts toward a 3 link these would allow the use of a 05+ Mustang 8.8 while mantaining about the same tred width. I saw a MII a while back that he had raised the rear wheel opening to the beltline and the front a bit less which opens your choice of tires and wheels a bunch and realy looked nice. It removed a bit of the coke bottle look.

[hssss]

Alcino
It took a while but I might have a spindle for you. I find I'm building 2 Lotus 7s. The first is a rebody of a V8 MII using generaly everything from the MII including the front crossmember and A arms. The second is a bit OTT the front suspension starts with MII but the A arms are 3" longer on the lower and an appropriate amount on the top. The spindle is from a 91 Tbird which is 1" taller .5 shorter from the lower balljoint to WMS and by the time I'm done the KPI will be smaller. The spindle can be modded to use the 99 to 04 Mustang GT PBR calipers which will result in lower unsprung weight. It can be easily converted to 5 on 4.5 by using 94 to 04 Mustang hubs which bolt on.
https://static1.pt-content.com/images/noimg.gif
https://static1.pt-content.com/images/noimg.gif

[JMarsa]

I'm interested in any more information Alcino has found since his purchase of the Chassisworks parts. I spent several hours a corner-carvers learning about the Mustang II. Then I found this thread.

--JMarsa

[fast Ed]

Alcino
The spindle is from a 91 Tbird which is 1" taller .5 shorter from the lower balljoint to WMS and by the time I'm done the KPI will be smaller. The spindle can be modded to use the 99 to 04 Mustang GT PBR calipers which will result in lower unsprung weight. It can be easily converted to 5 on 4.5 by using 94 to 04 Mustang hubs which bolt on.



Just FYI, the 93 - 97 T-Bird / Cougar spindles are the same overall dimensions, but incorporate a separate caliper anchor with the same mounting points as SN95 Mustangs, unlike the 89 - 92 spindles. So then you can pretty much bolt on any brake upgrades intended for an SN95 car. My 95 T-Bird Super Coupe is running the 99 - 04 Cobra 13" Brembo rotors with PBR calipers, which went right on my original front spindles.


cheers
Ed N.

[alcino]

What do you want to know about the Chassis works spindle? I returned mine. After checking them out I decided they were not for me. I hate adding weight, especially unsprung weight, and these babies were 50% heavier. (ductile iron may be "light", but there was so much more of it than the forged steel version)

I also hated the fact that the caliper bracket is casted on. Which forces you into using 11.75 rotors and wilwood dynalight bolt pattern calipers(note: I called them and they told me there was an additional bracket that allows 13"+ rotors, but all my stuff is the "popular" 12.19"). Why couldn't they have left off the casted bracket and kept the MII dust plate holes that are used for the bracket of all other kits?

Another thing was that the spindle was just a little too tall to fit inside my 15" wheels. Yes I like 15" wheels. Why? Because they are cheap and light and tires for them are cheap and light.

Plus after a track day of staying up with C5 corvettes and passing M3s (they had R compounds as well), I decided that my suspension is good enough. As long as your geometry is not dangerous, R tires will do way more for the money.

For those interested in the geometry, I took measurements on them. From what I gathered its geometry is the same as a 2" dropped MII, just the top ball joint is pulled up 7/8". Looking at Suspension analyzer I didn't find the Chassis Works to be much better than a 2" drop MII. It would give slightly better camber gain, but slightly worse roll center migration everything else equal. So what do you want more?

Alcino

[JMarsa]

Thanks for the the follow-up. I need to do some more home work on this and I might have some questions down the road. Love your car by the way!

--JMarsa

[hssss]

Just FYI, the 93 - 97 T-Bird / Cougar spindles are the same overall dimensions, but incorporate a separate caliper anchor with the same mounting points as SN95 Mustangs, unlike the 89 - 92 spindles. So then you can pretty much bolt on any brake upgrades intended for an SN95 car. My 95 T-Bird Super Coupe is running the 99 - 04 Cobra 13" Brembo rotors with PBR calipers, which went right on my original front spindles.


cheers
Ed N.

Unfortumatly that would be too easy.
https://static1.pt-content.com/images/noimg.gif

This is the 93 to 97 MN12 spindle which is WAY too tall to use in anything but a MN12. The 87 to 92 MN12 spindle has a boss stinking out where the hole in the above spindle iswhich is used to mount the earlier sway bar. To use in a MII style suspension you cut the top half off at that boss and use that for the top ball joint. Unfortunatly the 87 to 92 spindle is set up for the earlier single piston caliper and those are heavy as well as the cast in pieces to hold the brake pads. One of the holes for the caliper mount falls onto one of the holes for the dust cover and I'll have to provide the other.

alcino
I have some Dodge police rallys that are 15". Out of curiosity I'll check tomorrow whether these would seem to fit them.

[Tomswheels]

10 years later... Can we get an update?

[GrabberGT]

Yes. Please. Would really like to see what you did with the front suspension to stretch the wheelbase on this? Did you have to move the motor forward as well? Im thinking prob so do to the oil pan but... it would be nice if you didnt.

[killer69]

Here is the Chassis Works spindle next to the stock. Axle snout is the same. Not sure if the Balljoint taper is stock or Chrysler. But the most irratating thing is that they limit you to a 11.75" rotor with their cast in caliper bracket. ATS, please rescue us!
https://static1.pt-content.com/images/noimg.gif

what do you want?

[David Pozzi]

Alcino's latest mods are on his facebook page. I sent him a PM to check out this thread.
https://www.facebook.com/alcino.azevedo.7

[bryant]

chris, the motor stayed in the same place. just a fox oil pan swap was needed.

Alcinos car was one of the fastest cam cars before he did this stretch and now he says its easier to drive and has a better weight balance distribution. We have had 2 events this year with his stretch and hes on well used tires and hes right their at the top of the field. I suspect hes going to be a real challenge to the other couple of fast guys in our local cam class.

[alcino]

Thanks Bryant for answering while I been a bit busy lately. ...Tom?, not sure why your prodding this old thread after 10 years, although it was a fun trip through memory lane. Since there is some interest for an update I will continue the story.

The car setup remained as is described in the beginning of this thread until about 3 years ago when this whole SCCA CAM movement started. First thing to change was moving to a legal 200 tread wear tires. Running 15" tires limited me to 1 or 2 tire brands at the time. I was competitive, but many people were running tires as wide as 315s and I wanted to bridge that gap a bit.

So last year I did my first major changes. Which included: 17x10" enkie rpf1 +38 wheels, 255/40/17 Dunlop z2* tires, heidts 2" drop spindles, front coilovers and single adjustable Ridetech shocks. The 17" wheels/tires are a great compromise on weight/price and every brand makes the 255/40/17. Also per reading Ron Sutton's suspension theory's, I experimented adding lots of caster by relocating the lower balljoint 2" forward. Caster was about 8 deg now allowing me to use less camber to save the tires on the commuting. With this setup the car was gripping noticeably better on autox. Details here (https://www.facebook.com/alcino.azevedo.7/posts/1082578571768033)

I love autox again because of the CAM class. It's the do whatever, but be on the right tires class which lets you be creative and update your car in the true pro-touring spirit. One gripe was all my friends were in CAM-T and because of a year and wheelbase rule in 2015 I was regulated to CAM-S. A sub-class intended for corvettes and AC Cobras. I reluctantly raced in it while comparing my times to my friends. Then for 2016 they relaxed the rules a bit. The most important changes were that the year limit was pushed from 1972 to 1989 and the min wheelbase was reduced from 108 to 100"(thanks Fox mustangs and 3rd gen Camaros). So the only thing holding me back was my 96" wheelbase which initiated my "Christmas Break Stretch Goal" project.

My facebook post with the build details here (https://www.facebook.com/alcino.azevedo.7/posts/1290033264355895). In summary I "just" moved the front crossmember forward 6".

It was a lot of work. Seriously, a lot. I planned for 2 months so it would go smoothly and it still took twice as long as expected, but it was worth it. Just like Bryant mentioned the car is easier to drive. Stretching it to 101" took the front weight percentage from 56% to 50%. My manual steering feels like it has power assist. I also increased the caster to +11 deg with camber at -1.5. With my spindle Ron would recommend 13deg but I'm just going to drive it for a while as is. I hope to get new tires soon and am excited to see if it works even better.

San Diego is a CAM hot bed and I'm glad to be able to partake in the fun, camaraderie and competition. Tom is postings Race updates here (https://www.pro-touring.com/threads/119036-2016-San-Diego-SCCA-CAM-T-Race-for-the-season-updates) for 2016 if you care to follow along. Tom gives great tire info there.