# Does Tire tread depth matter for Track/Auto-X



## E36Shikara (Apr 16, 2007)

UPDATE:

This thread although helpful changed when I noticed the nail stuck in my tire therefore requiring a second plug in the tire alone PLUS the gouge in the sidewall where it appears that someone took a knife to it!!!

As I am sure all of your would advise, two new tires (S-02s) were ordered this AM and those oldies are going to be scrapped!

Thanks for all your advice... I am hoping that i'll have some miles on them before the autocross event on May 22nd!


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## bam2002 (Jul 17, 2007)

I have really never had tread squirm during an Auto X. Usually the speeds are to low. THe main issue on a stock car with no extra camber is wearing the outside edge of the front tires. OR if you have new tires you can tear chucks of rubber off the outside edge due to the tread flex.

If your doing a DE , then yes the car getting squirly and tread squirm can happen. But if you show up with badly worn tires they are not going to let you out on the track. most autocrosses have rules on tires below the wear mark.

I would use the new tires on the back of the car.

If you find you like Auto Xing go out and get a 2nd set of rims and some R compounds. They make all the differnce in the world. Once you use them you will never go back,.


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## cenotaph (Dec 19, 2001)

bam2002 said:


> If you find you like Auto Xing go out and get a 2nd set of rims and some R compounds. They make all the differnce in the world. Once you use them you will never go back,.


The autocrosses run by the Boston chapter of the BMW CCA (which includes all of MA and RI, and is at least one of the clubs the OP runs with) is mostly street tires for BMWs and MINIs. There is one R comp. class, but it's for very modded cars. We moved to this class system ~7-8 years ago, and we've had long wait lists for every event since.

I think that the popularity of the ST* SCCA autocross classes is mostly due to the use of street tires. R comps may be fun, but they cost $$$$. Especially if you want to be competitive.


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## bam2002 (Jul 17, 2007)

YEP. I run coil overs , nylon bushings, Camber and Caster in my 318ti with R compounds. I have taken 1st place for 2 year in that car. Then this year I am running a e34 on street tires for something different.
But Ill take R compounds any day.

We also run Auto Xs on a 150 foot wide runway that is almost a mile long. So the cars get up to 60 to 70 mph.. at that speed you need Sticky tires.


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## superbrew (May 14, 2009)

Wouldn't heavily worn tires be harder due to possibly having gone through may heat cycles? I know this is an issue with motorcycle tires, but those are a much softer compound.


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## E36Shikara (Apr 16, 2007)

So - I got the new tires on the car and it seems like I lost ALOT of tread during the 20+ runs that the car had on 1 day!!!! It was a dual driver car for the day:thumbdwn:

IN any case, I definitely noticed that the outside edge of my right front tire is worn down bald!!! You cannot even tell its a bridgestone tire anymore, because the name wore off....It's pretty bad - any thoughts on why this happened? The car just had an alignment... WHat gives?


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## Clarke (Oct 21, 2002)

Insufficient front tire pressure would be a likely culprit.Changing your braking/throttle usage for weight shift could help as well.


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## Clarke (Oct 21, 2002)

btw Sounds like a great day,not often you can get near a third of that many runs in a day at most events.:thumbup:


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## cenotaph (Dec 19, 2001)

Clarke said:


> btw Sounds like a great day,not often you can get near a third of that many runs in a day at most events.:thumbup:


We're pretty consistent about getting 8 runs per driver at every event. Occasionally, we have to cut it down to 7, and very rarely 6. I can't remember an event in the last 7-8 years where we got less than 6. And this is all with ~100 drivers at each event. About the only down side is that there is no lunch break.


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## Dave 330i (Jan 4, 2002)

There is more than just straight line grip in auto-x. New tires have much better turning respond than ball tires, which is more important than wide gripping type turns you see in raceways. I know, I just put on 4 fresh tires on my 330i and there is a big difference in turning respond.


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## BIMMERUSAM5 (May 20, 2007)

Dave 330i said:


> There is more than just straight line grip in auto-x. New tires have much better turning respond than ball tires, which is more important than wide gripping type turns you see in raceways. I know, I just put on 4 fresh tires on my 330i and there is a big difference in turning respond.


+1 Dave knows.


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## bam2002 (Jul 17, 2007)

I usually have to rotate the tires front to back then unmount them and go left to right since the outside edges always wear down. I would say get a set of camber plates if you plan to do this often. It will reduce the wear on the outside edges of the front tires.


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## 03BeastCharmer (Aug 29, 2007)

E36Shikara said:


> So - I got the new tires on the car and it seems like I lost ALOT of tread during the 20+ runs that the car had on 1 day!!!! It was a dual driver car for the day:thumbdwn:
> 
> IN any case, I definitely noticed that the outside edge of my right front tire is worn down bald!!! You cannot even tell its a bridgestone tire anymore, because the name wore off....It's pretty bad - any thoughts on why this happened? The car just had an alignment... WHat gives?


The E39 is a big heavy car. When I autox'd the M5 it killed my fronts quicky. I would agree 20 runs is a lot. We generally get 6 runs. If you can't see where it says 'Stones anymore, your pressures are really low, and you have a lot of rollover. You really need to bump of the pressures. You shouldn't see wear beyond the edge of the tread section. You also suffer from a lack of camber. Getting camber plates and running at least -2 deg of camber int he front will help with turn in and keeping a good contact patch. You may also be over driving. Complete your braking, then turn the car in. Be smooth. The E39 is a big car, and large movement will shift the weight and contact patch impacting your handling.

As someone pointed out about your original question. A bold tire may have more contact patch, but the rubber has been heat cycled and will have deteriorated some, and may not perform as well. I've replaced tires well before they were bold because they didn't grip anymore because they were old and on the verge of cracking (car wan't driven much, and texas run is painful on everything).


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## E36Shikara (Apr 16, 2007)

03BeastCharmer said:


> The E39 is a big heavy car. When I autox'd the M5 it killed my fronts quicky. I would agree 20 runs is a lot. We generally get 6 runs. If you can't see where it says 'Stones anymore, your pressures are really low, and you have a lot of rollover. You really need to bump of the pressures. You shouldn't see wear beyond the edge of the tread section. You also suffer from a lack of camber. Getting camber plates and running at least -2 deg of camber int he front will help with turn in and keeping a good contact patch. You may also be over driving. Complete your braking, then turn the car in. Be smooth. The E39 is a big car, and large movement will shift the weight and contact patch impacting your handling.
> 
> As someone pointed out about your original question. A bold tire may have more contact patch, but the rubber has been heat cycled and will have deteriorated some, and may not perform as well. I've replaced tires well before they were bold because they didn't grip anymore because they were old and on the verge of cracking (car wan't driven much, and texas run is painful on everything).


Thanks for the response! I recently bought some Winter wheels 235/45/17s all around on 8.5 inch wheels. The tires that are currently mounted are Kumho Escta SPTs. My thought is for the Autocross events I could drop down to these non staggerred 17s to burn away this cheaper rubber instead of the SO-2s which cost 3x more!... Any thoughts?


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