Specs on subframes?

[Fuelie Fan]

Sorry if I got under your skin, Tom, but the parallel you tried to draw between first-gen camaro leafs and corvette leafs seemed completely illogical, and that got me fired up.



I will also point out that despite my apparent complete lack of suspension knowledge, you chose not to disprove a single one of my points. If you can, by all means do, I'm here to learn as is everyone else. If any of my points were incorrect, please inform us. I have no problem being proven wrong, but just calling me dumb is grade-school immaturity, and I have no interest in getting into a name-calling contest.

Salt Racer, I will second CDog, unlike myself and others you are always very grounded, unemotional, and informative!

[Salt Racer]

Not always, but I try.

[Tom Nickols]

Ok to loose the emotion, my was only setting out to question the logic of spending lots of cash on the front end when it's basically ok, and leaving the rear end alone. To me this doesn't sound right. We cant proove easily that the new front end works, you're replacing like for like. But on the back, if you spent your cash there you could really make the difference, and a measureable one too.

No problem Fulie, I'm an engineer in the IRL, a Chevy fan and English. I just wish the imposible - Quad cams and coils springs!!!

[touring67]

Ok, so I have SOME info on a few parts but not much, however I will have more come Monday as most people close their doors for the weekend. Here are some specs on the DSE UCA's without the coilover kit. They offer 4-5 degrees of caster with caster lugs to easily adjust this while maintaining the same camber. Apparently these adusters keep the camber and caster settings seperate. The camber curve is LESS POSITIVE but not negative and not neutral. Apparently no one's bolt-on arms will bring the curve into the negatives. With just the UCA there should be no re-locating of the UCA mount and is not recommended for use with the Guldstrand mod. SECONDLY, if the coilover kit is purchased one will see 'improved' RCH but the actual spec is confidential. The camber curve will also become LESS POSITIVE, but not negative and getting closer to neutral. The coilover kit also IMPROVES bumpsteer but does not bring it to zero. However this can be adjusted with the steering kit. With this kit it is acceptable to lower the car without hampering the spring travel as it was designed for that. The price for kit 2 which is up to the coilover kit with arms etc is 2395. For full details check out their site. Ok enough with DS&E for now. Please, if anyone finds any discrepancies IN ANY of this please feel free to bring it up.

Since I didn't get the chance to talk to too many people I only have Art Morrison's IFS to talk about briefly as I don't know all the specs on it yet. It is lighter and quite strong but not really intended for road racing. This kit does offer zero bumpsteer and RCH is above ground but actual spec I won't know till Monday if not confidential. The caster is 2-3 degrees built in. As for the camber curve I don't know yet as its actual spec, along with RCH, is not available right now. ALSO, if anyone is interested these specs will be the same as on the Wayne Due frame. Wayne's frame is narrowed 3 inches however, so 275 mm tires shouldnt be a problem in the front and it weighs approximately 200 lbs less.

As for right now I don't think I know anymore but I will keep checking. I intend to check out 21st century, Alston, Fatman and some other aftermarket UCA makers. As for Corvette I don't know of anyone that uses it directly on a frame and I'm sure that everything would change if mounting points were changed so finding the specs might not be feasible. AND I know I forgot a bunch but that's all I can remember right now.

Bottom line...it will take a lot more than some simple bolt-ons to get perfect or even anywhere near perfect geometry.

[David Pozzi]

Salt Racer,
Keep me posted on your schedule, I'd like to see your car haulin around some corners, it felt pretty good on the salt at Bonneville!

Ive driven third gen's quite a bit and the lighter rear axle with no weight of leaf springs, felt a little better over bumps than leaf camaros I've driven. The third gen's feel very stable and predictable in the rear, probably very similar to a three link, I'd imagine. I should mention that third gen's have some problems with the front suspension that far overshadow anything that could happen at the rear.

Rear stability is even more important on my Lola T-70 since 65% of the weight of the car is on the rear wheels and the hp to weight is around 2.9 lbs/hp, if the rear isn't super stable, I can feel it right away!

[Salt Racer]

Salt Racer,
Keep me posted on your schedule, I'd like to see your car haulin around some corners, it felt pretty good on the salt at Bonneville!

Will do, David! I still had stock coils/shocks in the rear, and stock steering box - it feels much better now.


You're probably right that torque arm feels pretty close to 3-link. Perhaps 3-link may provide a bit more bite out of the corner due to higher AS. I can safely say the 3-link in my car is stable - I'm still alive!

..2.9 lbs/hp...

Nice!! One thing I notice about IRS on old racecars is relatively large scrub radius. You know, it'll be just like torque steer on FWD if you vary the amount of throttle while cornering, though it's probably hard to notice at the limit. Can you make longer arms and use rims with more offset? Probably not legal in vintage racing, huh?

[touring67]

Great post David, I thought it was very informative and pretty neutral, giving others the info they need to make their own informed decision. I am still debating 3 link over great leafs but since I will be gradually stepping up the 'abuse' in all forms of racing to this car maybe I should start with the system that offers a wider range of use and ability, not to mention more adjustable.

[David Pozzi]

touring67,
Thanks, I was hoping it would come across as pretty neutral since I don't have hands on experience with three link suspensions.

Salt Racer makes a good observation that if a somewhat torsionally "weak" subframe were tied in to a roll cage, it would probably be much stiffer than a stock sub unbraced. I agree with everything he has posted here. I think we both agree we wouldn't design a car from scratch with leaf springs but a highly developed leaf car is not that far behind a car with a three link but you can't tune a leaf setup very easily.

Look at a third or fourth gen Camaro with coil rear suspension, there is more room behind the axle for the exhaust and fuel tank.

[touring67]

I have a 3rd gen Camaro lying in wait in my garage at home. In fact it was my first 'car' and I learned with it. I like the rear setup torque arm and if you have ever removed the torque arm you sure know it works! The stock panhard bar does a nice job of locating the rear and when that is removed it gets pretty loose..not good. As far as your comment on the front suspension goes about third gens I think you are quite right. Although the rear feels quite stable the front doesn't handle hard corners too well even with 245 BFG kdw's. The strut suspension doesn't offer enough camber gain under hard cornering and likes to 'rub' the tires before it holds.

As far as what Salt Racer proposed with the skid pad testing and baseline settings I definately agree. I had been talking to Wayne and was sure I mentioned this before about the skidpad testing of different subframes. I say they can take a frame, build the geometry in and test it. It wouldn't be very accurate but it would be 'rough' as Salt Racer said which is good enough to compare in many cases.

Sorry btw, my name is Kyle.

[David Pozzi]

Kyle, With my IROC I had to brake in a straight line somewhat early and gently, the bumpstops in front are very close to hitting just sitting still. Hitting the bumpstops on hard braking causes one ft wheel to lock, makes you think the brakes are grabby but it's the suspension. If you enter a corner braking hard, the front end wipes out causing understeer. Normally a "good" first or second gen Camaro would get the tail end a little loose in that situation, or it can be made to get a little loose by trail braking it, but a third gen won't respond well at all. You have to enter slow then accelerate from apex out with a (stock) third gen, all due to the front suspension.
There isn't enough neg camber, I ran with as much as I could get out of the stock slots, couldn't mofify anything since we ran SCCA F stock autocross. I finished fifth in F stock one year at the SCCA nationals in Salina KS, with over fifty cars in our class. I got beat by the 1LE Camaros which have no factory air, that takes 80 lbs off the front end in addition they have better brakes and aluminum driveshaft.

If you were to remove a torque arm, I'd think you would be in danger of breaking your drive shaft. Removing a panhard bar would put a tire into the fender.

Back to testing, you could run around a skid pad, but even a flexable subframe could do that pretty well if you played with the settings enough. A better test would be a slalom, but that doesn't test how the car would enter a corner under braking.

Mark Donohue did a test where he drove the car around a four cornered course, it tests acceleration, braking, and cornering combined, but not transient handling like a slalom.

[touring67]

I have never run the car without the panhard or the torque arm but when you remove them you can tell they really make a difference. And as far as hard braking is concerned, yes the front always locks up despite it not being really that 'hard'. And that sounds like some pretty good driving there David! I read about that on your webpage as well. And as far as the stock A/C it is a huge weighty thing that I removed when I swapped engines. It is a monster! And thanks for the responses they are really interesting.

[David Pozzi]

The guy who won my class driving a 1LE was named Neal? Sapp, (forgot the first name) but he won the Mazda challenge where you make timed autocross runs in their cars at events all across the US, they have a US finals at the end of the year and he won it two years in a row!!! He won a new car each year.
Another autocrosser was Jeff Altenburg who is running IMSA events now. Randy Pobst is racing Porsches but started in autocross. Autocross taught me a lot but didn't teach me to concentrate for a half-hour of driving, when I first started track driving I was out of focus after three laps!

[ProdigyCustoms]

I have done one real world test, but without numbers. Only seat of the pants feel. We did a Chris Alston Chassis, a couple years ago. We took a car with all rebuilt suspension, urethane front bushings, good Koni Shocks, no aftermarket arms or any of that. A nice running and driving car. We put the car on the lift 3' in the air, put a engine crane and floor jack and supported the engine / trans in place. Unbolted the subframe and bolted the new subframe in. Took almost all of 2 days. Put the same tires and wheels on it and 48 hours after we drove it in, took it for a ride.
I am not an easy sell on changes. I have a real pet peeve for people that make a change to their car and let the change and claim seduce them into believing it helped. I see it all the time at the track, you run into someone in the staging lanes, I made this and that change, she feels STRONG! Only for them to gain nothing or go slower when the scoreboards are on. So I am a hard sell.
With that said, I will say there was an appreciable difference in ride quality. MAYBE, MAYBE, a bit better handling, but I might have been fooled by the better steering. The biggest advantage by far was the rack and weight savings.
We did not weigh the 2 complete set ups, but the CA set up was noticeably lighter, two guy's picking up one, then picking up the other. They claim 150LBS, it was an easy 100, and 150 is not out of line based on what I felt. This is with willwood brakes versus factory disc.
Funny enough, braking was the area I was least impressed with. It just did not feel any better. The brakes were not the killer 6 piston jobs, they were the 12" willwoods, but none the less, did not feel like an improvement, they surely were not worse, just maybe not better. They were much lighter.

My final report.

Improvements:

Steering - A BIG improvement, feel and terrific weight savings
Ride quality - A nice firm feel, nicer ride for sure
Weight savings - A lot, it did show up later on the time slip
Quality - Very nice quality

Non improvements:

Brakes - Was disappointed, hoped for more, but no worse
Handling - Was disappointed, no hard numbers, but did not feel much better, if any. Could have all been in the steering.

Summary:

I think the Chris Alston unit is great for a staightliners, or a Pro Streeter. Surely the best choice for those cars. For this group, that wants to tear up corners, I do not think there is an appreciable difference in handling, and the weight savings probably won't help as much as in a straight liner, except possibly with front to rear balance which is only so important.

Test car, 1969 Camaro, big block, Automatic, 245 / 60 /15 wheels / tires, urethane bushings all around, Koni's, your typical stocker.

[David Pozzi]

Thanks for the report on the Alston sub. I've seen their Chevy II sub and the Camaro sub and the quality of the parts is very high.
I've been thinking the Alston sub would make a good base for a PT car if there were a fiew improvements done. Like, - go over the geometry and make a fiew changes to optimize handling and insure suspension rigidity, and add some bracing to the crossmember.
Making a big block car handle well is pretty tough for any suspension. You can make them corner flatter and be better balanced, but they just aren't going to change direction very quickly with all that weight up front.

[touring67]

I am not sure how your braking tests where done but I was thinking that it might be quite possible that those brakes weren't seasoned/bedded and that would most definately give you a poor braking feel. You might have broken them in beforehand and maybe they were still poor after that, I don't know, just a thought. The quality does seem to look good on the Alston clip though, however I think I read it as having room for 225 mm tires in stock fenderwells though, maybe not but that is what it alludes to on the website.

[Jagarang]

I can't read all the posts do to a lack of time, but if it hasn't been mentioned yet, here's my problem with "quantifying" change. It's been SOOOOOOooooooo long since I've even had a seat in my car, much less driven it, that my change to a WD sub-frame will be nearly impossible for me to offer even a seat of the pant's impression. On top of that, the car has had such a copious amount of significant modification that it really won't even be the same animal anymore, I don't imagine. At this point really it will be the greatest pleasure to just see the damn thing in one cohesive piece, get in it, crank it, and stomp the go peddle and hear it, feel it, and smell it! I don't think I'll really care much about how MUCH better each individual system/component might be, but OVERALL the car will be world's above what I started with and a complete restification, done the best I could afford to do even if I couldn't do the work myself (which hurts).