Aaron, Donna win at Huntville.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Aaron Buckley wrote:

Karl is probably correct. We're going to get a camber guage and level the garage. Then we'll pull a spring up front and measure the car at different points on the camber curve. If what I suspect is correct, some caster adjustment may help. We're also going to take it to alignment specialist that will loosen the entire front suspension to remove any slop and maximize camber.

That would be my first assumption too. On the C5 a fatter sway bars do help. The biggest reason we see camber change is the rubber bushings in the control arms. Swapping them to poly makes the camber pretty consistent though even the hardest cornering. I know you can't go poly in stock class but it's something to check to see how much they are compressing. If I keep caster at 7deg then the car feels good and I don't give up camber. I don't suppose you can get more static camber in it?

Karl Shultz · **Posted:** Mon Jun 04, 2007 7:04 pm

Graham Jagger wrote:

That would be my first assumption too. On the C5 a fatter sway bars do help. The biggest reason we see camber change is the rubber bushings in the control arms.

Good point, and something to consider when checking out the camber curve in a garage. You guys won't be able to generate anywhere close to the amount of lateral load you do when you're on course with the car up on stands. So look around for suspect looking soft bushings and whatnot. It's a car with sort of a luxury bend to it, so I suspect there's lots of them.

In any event, Aaron I'm glad the car is fun now (even if keeping it in tires is not). You guys didn't seem real pleased with the decision in Sanford, so I'm glad it's working out to the good. Remember, if you guys decide to not drive the Crossfire, and I've got a seat open, you're welcome to codrive the S2000 with me.

JamesFeinberg · **Posted:** Mon Jun 04, 2007 7:49 pm

I think it's very important not to lose sight of the big picture-- keep telling yourself how much fun race tires are!

But seriously, that does suck. Hopefully you guys will get something figured out. Keep us updated on what you hear from the Hoosier guy.

I watched all of the Saturday runs this weekend and the car looked real good despite the cording issues. On the first couple of runs, it had that perfect "dance" look that fast AutoX cars seem to exhibit. You could definitely tell when the tires started going off big time and it's a shame you guys never got to see the full potential on subsequent runs.

Jim

Chuck Branscomb · **Posted:** Mon Jun 04, 2007 8:44 pm

Aaron Buckley wrote:

We ran 10 runs at Sanford and 4 practice runs at Huntsville (medium grip asphalt). On my first run of the event, the driver front started to cord the outside edge. Yes, on the 15th run. :shock:

Wow, does this sound familiar: http://thscc.com/phpBB/viewtopic.php?t=5287

Since then I added a 27mm front bar and set it to full stiff (a bit over 1" less moment arm than stock, stock diameter was 24mm). I have the front camber max'd at -1.2 degrees, toe at zero. The camber curve with compression is reasonable (for a strut suspension) on the 330i I think; caster is about 6 degrees at static height.

Jeff probably won't really have much to say other than "raise the air pressure", but perhaps you can get some help from him. Is it possible that you are seeing major bushing deflection at full lateral load or something similar? Also, dang, I had no idea you have a ~500lb weight advantage over the 330i zhp! :shock:

I think I'm going to try to find someone to mount/air up the V710 245/35 on my 8" and 8.5" rims again before the DC event. My other option is to run 285/30-18 all around since from the measurements I made, I "think" these will just fit on the car. If I go that route, I'll stick with the A6 probably in order to be more able to mount/air up the tires.

Chuck

Keith Vail · **Posted:** Mon Jun 04, 2007 8:57 pm

Aaron Buckley wrote:

You're looking at the 275's? With the upper arm bolt, I don't think they will fit, even with spacers. We're just going to suck it up and buy a set of 245/35/18 Kumhos and put them on the two sets of front wheels we'll have. I don't think that the tire width is the problem, for the car never pushed at all, even with the 30mm bar... that is until they corded.

Nope the 285s. They are shorter than the 245 by a smidge and will be fairly pinched on the wheel. If they don't I will be on the 245 Kuhmos for DC as well probably.

Keith Vail · **Posted:** Mon Jun 04, 2007 8:59 pm

JamesFeinberg wrote:

But seriously, that does suck. Hopefully you guys will get something figured out. Keep us updated on what you hear from the Hoosier guy.

I emailed Hoosier and no one ever even responded to me. Needless to say I am a bit annoyed. When the front tires are aired up to 55 psi they should not be rolling on the cord that much. I may be on street tires again next year in a different car.

Ryan Holton · **Posted:** Mon Jun 04, 2007 9:43 pm

Keith Vail wrote:

I emailed Hoosier

That's funny. I bet you would have had better luck calling someone.

MarcusMcRae · **Posted:** Mon Jun 04, 2007 10:03 pm

Chuck Branscomb wrote:

Also, dang, I had no idea you have a ~500lb weight advantage over the 330i zhp! :shock:

Chuck

You're forgeting it's really a BS car. :wink:

Chuck Branscomb · **Posted:** Tue Jun 05, 2007 7:19 am

MarcusMcRae wrote:

Chuck Branscomb wrote:

Also, dang, I had no idea you have a ~500lb weight advantage over the 330i zhp! :shock:

Chuck

You're forgeting it's really a BS car. :wink:

Whoops! Thought he was talking about the DS Crossfire. :oops:

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

Chuck Branscomb wrote:

MarcusMcRae wrote:

Chuck Branscomb wrote:

Also, dang, I had no idea you have a ~500lb weight advantage over the 330i zhp! :shock:

Chuck

You're forgeting it's really a BS car. :wink:

Whoops! Thought he was talking about the DS Crossfire. :oops:

He is.

Chuck Branscomb · **Posted:** Tue Jun 05, 2007 7:25 am

Wes Eargle wrote:

Chuck Branscomb wrote:

MarcusMcRae wrote:

Chuck Branscomb wrote:

Also, dang, I had no idea you have a ~500lb weight advantage over the 330i zhp! :shock:

Chuck

You're forgeting it's really a BS car. :wink:

Whoops! Thought he was talking about the DS Crossfire. :oops:

He is.

Ah, got it now...double :oops:

and

That'll teach me to reply without thinking so early in the morning.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Ryan Holton wrote:

Keith Vail wrote:

I emailed Hoosier

That's funny. I bet you would have had better luck calling someone.

Yes! Call them. Email is almost a waste of time. I've spoken to them a few times about the A6/R6/Rolex tires. They will return calls pretty quickly if they aren't available when you call.

On cording the outside edges. They will tell you -2.0 degrees camber in the front is a bare minimum. Preferably -3.0 degrees on any of their tires. Over-inflating them is just a band-aid. On track I go for 40lbs hot. With -2.0 camber I see some wear on the last 1/2-1" of the tire. If you can run same size tires on all 4 corners then swap front to back early and often. Or try some V710s. They seem to be less camber needy.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Karl Shultz wrote:

Graham Jagger wrote:

That would be my first assumption too. On the C5 a fatter sway bars do help. The biggest reason we see camber change is the rubber bushings in the control arms.

Good point, and something to consider when checking out the camber curve in a garage. You guys won't be able to generate anywhere close to the amount of lateral load you do when you're on course with the car up on stands. So look around for suspect looking soft bushings and whatnot. It's a car with sort of a luxury bend to it, so I suspect there's lots of them.

If the geometry of the Crossfire suspension is similar to the C5. Then I would inspect the lower control arm bushings very carefully. As Karl said, getting a good reading in the garage with static loads might be tough. C5's tear up lower control arms, and more so as camber is increased. Look at the bushings outer lip and see if they are compressed or wallowed. Same where the bolts go through. Since the Crossfire is pretty new they should look good.

Btw, Are the end links for the sway bars plastic by any chance? I know the earlier C5s came with them then they swapped to metal on the Z06. It made a big difference.

Aaron Buckley · **Posted:** Tue Jun 05, 2007 10:55 am

Graham Jagger wrote:

If the geometry of the Crossfire suspension is similar to the C5. Then I would inspect the lower control arm bushings very carefully. As Karl said, getting a good reading in the garage with static loads might be tough. C5's tear up lower control arms, and more so as camber is increased. Look at the bushings outer lip and see if they are compressed or wallowed. Same where the bolts go through. Since the Crossfire is pretty new they should look good.

Btw, Are the end links for the sway bars plastic by any chance? I know the earlier C5s came with them then they swapped to metal on the Z06. It made a big difference.

With the car about 21 days old and about 1k miles on it, I'll assume the bushings are fine. The swaybar came with delrin bushings and there are no endlinks for the front bar. It basically mounts into a slot within one of the control arms and there's very little if any slop. I think the bar change took about 25 minutes and could now be done in about 10 minutes

The CCW's are now ordered and we've decided to say the hell with contingency and run Kumhos up front and Hoosiers in the rear. At this point, I don't even want to think about tires cording out that quickly, or even the possibility of it. I think that Hoosier will likely give us another set of tires, and I'll want the 235/30/19 rears. - AB

Chuck Branscomb · **Posted:** Tue Jun 05, 2007 11:16 am

Graham Jagger wrote:

On cording the outside edges. They will tell you -2.0 degrees camber in the front is a bare minimum. Preferably -3.0 degrees on any of their tires. Over-inflating them is just a band-aid. On track I go for 40lbs hot. With -2.0 camber I see some wear on the last 1/2-1" of the tire. If you can run same size tires on all 4 corners then swap front to back early and often. Or try some V710s. They seem to be less camber needy.

I agree with all of the above, especially about the band-aid "pump them up to 50+psi" BS. Imagine what happens to the contact patch of that front tire, under load, at say 54psi. As you increase pressure in order to gain sidewall spring rate and reduce rollover, you also reduce the contact patch size. Reducing the patch size increases the loading on that patch (i.e. same maximum normal force now spread over a smaller patch area) which can only lead to higher local tread temperatures in addition to a sub-optimal patch size/shape. Past some threshold, increasing the pressure will probably actually increase the cording probability imo. That "threshold" likely varies for different cars, wheel widths for given section width, etc. Hoosier seems to be shooting from the hip with their recommendations. I’ve just come to the conclusion that if I can’t run at least -2.0 degrees of camber on the 330i, A6s are just not worth using. (Wouldn’t it be nice if the SCCA allowed camber plates in stock class? Think of the money it would save on tires, and then they could help equal out cars that have more adjustability standard versus those that are fixed).

The Hoosier guys didn't really care for my opinion expressed to them that the A6 is not the right tire for many stock class cars that are camber challenged, but I still think that is the case. V710 here I come I guess. If I ran Hoosier, I would have my engineers tasked with coming up with a state-of-the-art breakthrough design A8c tire design specifically for severe camber challenged stock class cars...come out with an A8 and an A8c.

Chuck

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