Aaron, Donna win at Huntville.

Aaron Buckley · **Posted:** Tue Jun 05, 2007 11:33 am

For those that like carnage, enjoy the 20 runs of hell:

Notice at the far right the tread depth indicator. Yes, it's near full 4/32".

Another:

That's how the tire looks all the way around on both driver and passenger fronts.- AB

Chuck Branscomb · **Posted:** Tue Jun 05, 2007 1:02 pm

Wow, that almost looks like it was rubbing something? That is pretty sick as you can see the tread depth hole just a short distance away from the cord area with plenty of depth. That looks worse than what I saw on the 330 prior to adding the front bar. This doesn't look like something air pressure is going to solve or be of much help unless you were running something around 40 or under...what pressure were these run at?

Aaron Buckley · **Posted:** Tue Jun 05, 2007 1:17 pm

We were at 48# cold and kept them there when they were hot. Obviously, the pictures show that to be the inside edge because they were flipped on the rim after day 1. - AB

Chuck Frank · **Posted:** Tue Jun 05, 2007 2:45 pm

We did that to the first set on the front of the Solstice. It was a combo of too little camber and making the car push severely in the corners from driving in too deep.
After adjusting the camber and our driving style we are now getting 80+ runs with a midway flip.
In fact after flipping the set we had edge corded we ran them in the Evo Extreme school and they never showed any additional cord on either edge.

Donna Frank · **Posted:** Tue Jun 05, 2007 2:55 pm

Chuck Frank wrote:

We did that to the first set on the front of the Solstice.

Yep...and I was seeing $ signs dance in my head for a couple of days. :shock:

Chuck Frank · **Posted:** Thu Jun 07, 2007 11:31 pm

Aaron, Keith,
does the crossfire have any type automatic stability control? We ran the first test and tune with the stability control engaged (we hadn't yet learned that turning off the traction control does not necessarily mean you have also turned off the ESC :oops:

) when we corded the Soli fronts like that. I think the ESC was locking the outside wheel brake in the sweepers causing the tire to roll over and slide. I'd bet that if it does have it, turning the stability control off completely if possible would end your tire wear issues.

Donnie Barnes · **Posted:** Thu Jun 07, 2007 11:53 pm

Not only does the Crossfire have it, but there isn't any way to completely disable it from what Aaron has said. That could very well be a contributor to the problem. I swear it doesn't seem like the car could be going positive camber, and having around 1.5 degrees of negative camber up front isn't ideal, but shouldn't cause *this* kind of problem.

--Donnie

Chuck Frank · **Posted:** Fri Jun 08, 2007 12:50 am

Donnie Barnes wrote:

Not only does the Crossfire have it, but there isn't any way to completely disable it from what Aaron has said. That could very well be a contributor to the problem. I swear it doesn't seem like the car could be going positive camber, and having around 1.5 degrees of negative camber up front isn't ideal, but shouldn't cause *this* kind of problem.

--Donnie

But trying to drive thru the ESC will. The method to turn ours off completely is not documented in the owners manual, perhaps they is an undocumented method for the CF as well? Since we learned how to turn ours off completely we are getting >80 runs on a set of tires.

Aaron Buckley · **Posted:** Fri Jun 08, 2007 7:41 am

Our FSM is about 1700+ pages, and has no mention of how to fully disable it. The Crossfire forums are a bunch of waxers that are constantly asking what is the best swirl remover.

Outside of Keith, myself, and guy out west that gutted his and put a cage in it for track, there are no real knowledge about the car. The ESP/TC even when 'disabled' never fully cuts off. The Mercedes SLK320 version has what's called 'dyno mode' which completely shuts the ESP/TC off, but Chrysler execs chose this as not worthy.

Here's an interesting tidbit: There has not been a single person to get a dyno run on the Crossfire. Why? Because the ESP will sense that the front wheels aren't spinning, put the car into limp mode and not let it rev above 5k rpms. Lovely :roll:

Now, autocross wise, with the ESP/TC 'disabled', outside launching too hard and spinning the wheels, unless you actually get the car really loose or push horribly, the ESP will not interfere. I've only had it kick in a couple of runs where I was trying to make it kick in.

To me the cord is a function of Hoosier tires not doing well with less than -2 degrees of camber. I may be wrong and we find out that the Kumhos can't stand it either. - AB

Chuck Branscomb · **Posted:** Fri Jun 08, 2007 7:47 am

Aaron Buckley wrote:

I may be wrong and we find out that the Kumhos can't stand it either.

245/35-18? Rim width?

Chuck Frank · **Posted:** Fri Jun 08, 2007 12:52 pm

Try holding the button in for a period of time, 10 - 30 sec rather than a quick push, that's how our's works. Ours requires ~ 15 sec before everything shuts off. I do believe the ESC or whatever they call it is at the root of your problem, it may be slowing the wheel enough to cause it to roll over and drag without you being aware of it. There was no feel of it on the Soli except the car wanted to push a bit coming out of the turns. We have not had a problem with A6s edge cording even on the Miata where 1.9 was all the front camber available except that first set on the Soli and we were running 2.0 at that time. Since turning off the ESC we are getting 45-50 runs without any sign of cording before flipping the tires.

Donnie Barnes · **Posted:** Fri Jun 08, 2007 1:23 pm

Tie the DL-1 to the wheel speed sensors you already have. The data will tell you if it is the ESC braking the wheel or not. It's a lot of wire to run through the firewall, but it actually shouldn't be hard to do otherwise. I think there is a good chance that Chuck is right.

--Donnie

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Another idea -- try adjusting the brake light switch so it's on all the time and check if traction control is disabled. It's an interesting idea - see the post below (about other chrysler products):

Quote:

Bulvot9/8/2004 4:12:49 PM

I have some not inconsiderable experience working with modern traction control systems with respect to trying to get them to function properly in extreme environments. I am not directly familiar with the traction control system used on the LX platform (which I believe is the same one used on the AUDI's?) but if it works the same as all of the other traction control systems I've seen, there is a very easy way to completely disable it at will.

Bear with me as I explain how a typical traction control system functions and why it is so easy to get it to stop working.

Your car has a differential that splits power between the left and right wheels. For simplicity's sake, let's assume that it has a ratio of resistance under which the power will go to both wheels. If the ratio of resistance between the wheels exceeds the ratio the differential is designed for...all of the power will go to the wheel with the least resistance. In other words, both wheels on dry pavement...both wheels have the same resistance (from the contact with the pavement). Lift one of the wheels up and the resistance of the wheel in the air approaches zero and all power goes to that wheel.

It is possible to use the brakes to bring that resistance ratio back within the tolerance the differential was designed for. If you apply the brake with the pedal, brakes are applied at all four wheels so you have to apply pretty significant braking force to get the ratio where you want it.

Yes, this really and truly does work in the real world on some types of differentials. Specifically it usually works on limited slip differentials (it's worked on all the ones I have tried it on) and it always works on a Torsen differential (my preference for this type of maneuver). Fully open differentials require a lot more braking power which puts a lot more stress on everything so don't count on it working there.

Now, if you coul just apply the brakes on the one wheel that's in the air, you only have to apply enough brake to create enough resistance to bring the resistance ratio back within the tolerances of the differential. This is the most effecient application of the brakes to achieve the desired result.

That is how modern traction control systems work. They detect wheel spin and when one wheel has execessive spin it applies the brakes to that wheel alone, which transfers power back to the wheel that still has traction.

With that rudimentary understanding of traction control systems (along with my made up term of resistance ratio), you can imagine that if you apply the brakes at the same time that the traction control system is trying to do its thing...there's a conflict. Traction control systems usually preclude that conflict by deciding that if the brakes are pressed, you're trying to stop, if the brakes are off, you're trying to accelerate.

What this means is that if you apply the brakes while accelerating, the traction control system will assume you are trying to stop and will modulate the brakes if it detects wheel lock-up (modulate = release for our purposes) but it will not apply the brakes. Yes, this is really the way it works in the real world. If you're trying to get traction control to help you out and you tap the brakes...traction control cuts out.

This begs the question...how does the traction control system know when you are applying the brakes? In the ones I have worked with, it's via a sensor on the brake pedal control arm under the dash. In other words, a mechanical switch.

If the Magnum functions the same way (and I have every reason to believe that it does) then if you wire in a remote toggle switch to the brake pedal sensor, you could effectively cause the car to think you are braking by just flipping the switch. Of course, this would cause the brake lights to come on, but it should also disable all traction control.

The only point that I am not sure about is the braking assistance that the LX platform provides. I do not know exactly what its operating parameters are but I would be concerned that it may apply the brakes on your behalf if it believes the vehicle is accelerating while you want to stop. I don't think this is likely to present a problem for our application, but it is something to consider.

If you are good with left foot braking or heel/toe, you could achieve the same result by just lightly touching the brake pedal. Enough to cause the lights to go on but not enough to actually engage the brakes.

I don't know if a CAN scan tool will be able to tell you when traction control is working the brakes, but if so you should be able to easily test and prove the above information.

Chuck Frank · **Posted:** Fri Jun 08, 2007 5:40 pm

That's traction control. Traction control only affects the drive wheels. The issue with the tire wear is due IMHO to the stability control, a separate system from traction control which has a number of different trade names such as ESC (electronic stability control in GM products) Stabiltrack, anti-skid etc. where the wheel speed sensors work in conjunction with yaw sensors, steering angle sensors, throttle position, etc to sense when the car is entering a attitude that is possibly going to result in loss of control or spin. When an impending spin is detected the wheel brakes are independently applied to try to force the vehicle back into a straight line. In a vehicle with ESC on when you enter a sweeper at high speed the system will start applying braking to the outside front wheel and inside back wheel to try and straighten the turn. If you then turn the wheel further or try to throttle steer, the steering sensor and yaw control detects you have the wheel turned too far for the turn radius and/or the rear is starting to hang out and it will then add additional rear braking to both rear wheels and chop the power.
You can think of the two systems in terms of what you might need in driving on an icy road: To get moving, traction control will help keep you from spinning the wheels. Once moving, stability control helps keep you from spinning as you go around a corner. Unlike traction control trail braking will ACTIVATE ESC rather than shutting it off.
The Soli has 4 different mixes of the two functions you can choose:
1. TC and ESC on (default)
2. TC off ESC on (traction off)
3. TC off ESC reduced (competition mode)
4. TC and ESC off (manual mode)

Chuck Branscomb · **Posted:** Wed Jun 13, 2007 5:24 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:

Bryan drove his first and the passenger front began to cord. The cord caused the car to push on our 2nd runs and our third runs had the steel belts coming undone. Not fun.

Well, I'm back again with the same issue using the two new A6s Hoosier sent me late last summer to replace the others that corded. We ran the brand new ones up front on the 330i zhp starting at 52 psi as directed by Hoosier. This year we have a large front sway bar on the car, toe is zero, camber full max which is around -1.2 or so.

After a total of 8 runs at Sanford, I flipped the fronts on the rims this past Saturday (thinking ahead about how hard L'burg is on tires). So starting on Sunday we had perfect outside edges on the fronts with the little tickys showing even. By the end of run number 8, cords were starting to show on that outside 45 degree angle thing the A6 tread face makes (i.e. just like Aaron's picture), and by the end of run 10, the tire was totally wasted.

I'm done with Hoosiers...have some BFG R1's in 265/35-18 on the way. These might not be the best for autocross, but we'll hopefully get some decent wear out of them. I can't find anyone around who has tried these for autocross, so I'm the guinea pig.

Back to the A6 for moment…that “outside 45 degree angle thing” I mentioned up above refers to how these tires wear on their shoulder. After the morning runs at Laurinburg, I noticed what looked like a 45-degree ramp angle wearing on the shoulder (as opposed to a nice rounded wear pattern you typically see on tires). You could actually see the main tread face belt/tread thickness, then the 45-degree angle wear down to the sidewall support structure. I’ve never seen something like this on any other tire over a zillion years of tracking and autocrossing. It’s like the tread compound is too thin and not properly supported in this section of the main tread face to sidewall junction. If you look at Aaron's picture, you can see the semi-depression the tread makes along the shoulder where the cords appear.

I can post pics later if anyone is interested.

Chuck

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Aaron, Donna win at Huntville.

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