Tire wear after 1st autocross

[Oofie]

My brother and I just did our first autocross event in his new 135i. It was first time for the car but not for us. We had a brand new set of 235/45/17 Dunlop Direzza SS on old Kosei K1s. The car, was a blast to drive although there was still some understeer during the very slow tight corners.

Anyway, this was the outcome of the front tires after 22 runs. Tires were around 41-42psi hot.

Left Front:





Right Front:





Is it normal that most of the uneven wear is on the middle part of tire? I thought we would be wearing out the outer shoulder, but from the looks of it, it's mostly the middle part that has uneven wear. Is this a sign of over-inflation?

[Focusedintntions]

Yes it is. If oonly the outer edges were warn it'd be under inflation, if only the middle gets worn it's over inflation. Ideally you want even wear across the whole surface so try bring down your psi to around 38 hot. If you can't tell by wear what your tires are doing get a thermal heat gun and check the temps for even ranges across the tire.

[DriveHard]

22 runs in 1 day ??? if thats the answer, then those tires were over heated and that is your result.. al the rubber smeared over to he inside.

focusdef gave you a standard answer..( which is true BTW)

the wear you are seeing in the middle really isint wear per-say.. it is a result of the lack of camber and the tire dragging across the pavment and creating the distinct wear patterns during hard cornering..

The real question should be, what do your outer shoulders look like? that would be the key for tire pressure... If you rolled over onto the side wall too much than you need to up the pressure, if you didnt rollover enough, you need to lower the pressure.. fronts in our cars need more pressure usually if you are camber defecient.. not so much if you have camber plate installed.


do you know how to mark your tires with shoe polish to help aid in telling if tire is rolling or not ??

After a day of auto-x i like to keep the tires on for one more day and "even them out" if i can and its not going to rain...

I run a square set up ( Hankook Rs3's ) so i even get to rotate so as not to beat up 1 tire all the time.

[BrokenVert]

My fronts looked like that last year

[Oofie]

@Focusedintntions, I forgot to bring our heat gun, but we'll do that next month.

@Drivehard - Yes, we did 22 runs for the whole day. It was 4 runs each in the morning(4 runs per driver), 4 runs each around 1pm and 3 runs each around 3pm. Outer shoulders look fine, but we noticed that after the first 8 runs, pressures were about 39-40psi and the little triangles on the shoulders were gone. So we raised it a bit to get 41-42 hot and this happened. Of course we're not sure if this was the case even during the first 8 runs while they were 40psi hot.

Good thing that this is a square setup also, at least we can rotate then flip them after a few months. By the way, tires were just taken out today, so they've been in the car for about 3 days of normal driving.

[DriveHard]

WOW.. it must of been the 8 runs back to back... with the 2 drivers..

you nailed it with the triangles, i didnt know if you knew that

Ive got 4 full blown track events, and maybe 10 auto x's on mine, and they dont look that worn / beat up.. ( i have no camber plates, but i did pull the pins and get about -.75*)

your pushin' hard

I rotate front to back every event, and then flip them side to side at the beginning of the year..

[Oofie]

Originally Posted by DriveHard

WOW.. it must of been the 8 runs back to back... with the 2 drivers..

you nailed it with the triangles, i didnt know if you knew that

Ive got 4 full blown track events, and maybe 10 auto x's on mine, and they dont look that worn / beat up.. ( i have no camber plates, but i did pull the pins and get about -.75*)

your pushin' hard

I rotate front to back every event, and then flip them side to side at the beginning of the year..

Yeah, we had to do back to back twice (during the 4 run sets) and they destroyed the tires. Next time we'll make sure to let it rest or just bring a water sprayer (good idea?). We're also learning how to drive the car, as it's really different from our previous Z4. This really has more understeer and push, but definitely more stable coming out of corners. The Z4's rear always wanted to step out even with 255's, but this car was more stable with less tires (235).

Good thing was I was 1st in class and my brother 2nd in class. 14th and 18th overall, with only modified M cars, modified Miata's and 2 STI's in front of me. Fastest stock car of the bunch

[BrokenVert]

Not sure if this has been discussed.

But the triangle represents where the tread ends and the sidewalk begins...that's where you want the wear line to be

[Oofie]

Originally Posted by BrokenVert

Not sure if this has been discussed.

But the triangle represents where the tread ends and the sidewalk begins...that's where you want the wear line to be

Correct! during our first set of runs, we completely destroyed the triangles, so we knew we had to up the pressure a bit. We raised it about 2-3psi and this happened. I guess we'll have to play again with pressures next event and make sure to bring a water sprayer to cool the tires down especially with 2 drivers.

[DriveHard]

Originally Posted by Oofie

Yeah, we had to do back to back twice (during the 4 run sets) and they destroyed the tires. Next time we'll make sure to let it rest or just bring a water sprayer (good idea?). We're also learning how to drive the car, as it's really different from our previous Z4. This really has more understeer and push.

Good thing was I was 1st in class and my brother 2nd in class. 14th and 18th overall, with only modified M cars, modified Miata's and 2 STI's in front of me. Fastest stock car of the bunch

If you are doing back to back driver runs, then def get a water sprayer.. also when you change drivers, go to the back of the line to help the tires cool off.

although coming in first is great, tearing up tires is not so great.. and it aint cheap either.... im sure that you'll dial in the tire pressures and driving style.. maybe search a little "star spec" tire pressure and see what you find ???

regards.

congrats on the 1st place BTW ... thats the way to teach those pesky Miata's ( i have one of those too LOL)

[MarkR171]

I run my star specs at 45psi hot in front and 40psi rear. I have to run that high in the front to prevent rollover onto the sidewall. Never had a problem with wear like in your picture, but my runs are 2nd gear max speeds and over in 40-45 seconds. Max 8-10 runs in a day with at least 5 minute wait between runs. 12k miles, a full autocross season (at least 80-90 runs total) and the tires should still be good for another 3-4k.

[Oofie]

Originally Posted by MarkR171

I run my star specs at 45psi hot in front and 40psi rear. I have to run that high in the front to prevent rollover onto the sidewall. Never had a problem with wear like in your picture, but my runs are 2nd gear max speeds and over in 40-45 seconds. Max 8-10 runs in a day with at least 5 minute wait between runs. 12k miles, a full autocross season (at least 80-90 runs total) and the tires should still be good for another 3-4k.

For this particular course, it was mostly 2nd gear, but there's one part where we were doing 85-90mph before a 5 cone decreasing distance slalom. Fastest I ran was 100.56, my brother did a 101.39. Fastest BMW was an e36 M3 with unknown mods, 97.6 seconds.

I think DriveHard answered it perfectly, we were overheating the tires with back to back runs. We definitely have to take care of the rears (which will be fronts next time) to make them last.

[DriveHard]

Originally Posted by Oofie

For this particular course, it was mostly 2nd gear, but there's one part where we were doing 85-90mph before a 5 cone decreasing distance slalom. Fastest I ran was 100.56, my brother did a 101.39. Fastest BMW was an e36 M3 with unknown mods, 97.6 seconds.

I think DriveHard answered it perfectly, we were overheating the tires with back to back runs. We definitely have to take care of the rears (which will be fronts next time) to make them last.

Rotate those tires to the rear for at least 2 events... let them recover a little.. then address your pressures as needed up front and dont start off to low. use the water sprayer ( got mine at home depot on sale for like 9 dollars ) check the pressures after each run, dont be scared to pull out of line and get some air form your pit... you'll have plenty of time espically with your brother there..

Have fun..

[Oofie]

Thanks DriveHard! I'll update this thread in 5 weeks after our next 2 driver autocross.

[Amalfitano]

also a generic note, that was some deeeep tread, the heat probably never got all the way into the tire and heated up the surface even more with the extra rubber to deflect.. Quite a few guys locally spray every run no matter what with the first few 32nd's.

[135forthewin]

Pushing the limits on a set of brand new tires is never a good idea...

Even though they are a street tire, some heat cycling (only needs about 800-1000 miles of normal driving) will give them a bit more grip and durability.

I'm no track junky, but I've been told the same thing by competitive racers who run the star specs on their street cars for track days.

[satakal]

I see tire wear in these pics. I don't see overheating. In my experience, tire overheating leads to a sensation of lower grip, and tire chunking. In these pics, I see a tire that was pushed (not rolling) across an abrasive surface.

I would like to emphasize that those are the fronts only that look that way. When the wheels are turned, and the car's mass is traveling forward, it's cheese greater-to-tire type wear. The leading edge takes the majority of the wear.

Once a driver is fast enough (congratulations!), what he does to a tire is more "abuse" than "use". The driver has 2 choices. Lessen the abuse by slowing down, don't push the front end, slow in fast out, etc. Or buy a more purpose designed tire.

You guys, in that car, on those little tires, were so fast. Very well done. Did you beat the camaro with the e36 body on it? Also, when was the last time you guys had times that close together? Maybe we can conclude the e82 is easier to hustle than the z4?

[jeremydgreat]

These are exactly how my Starspecs looked after a couple events. Woohoo!

[Oofie]

Originally Posted by satakal

I see tire wear in these pics. I don't see overheating. In my experience, tire overheating leads to a sensation of lower grip, and tire chunking. In these pics, I see a tire that was pushed (not rolling) across an abrasive surface.

I would like to emphasize that those are the fronts only that look that way. When the wheels are turned, and the car's mass is traveling forward, it's cheese greater-to-tire type wear. The leading edge takes the majority of the wear.

Once a driver is fast enough (congratulations!), what he does to a tire is more "abuse" than "use". The driver has 2 choices. Lessen the abuse by slowing down, don't push the front end, slow in fast out, etc. Or buy a more purpose designed tire.

You guys, in that car, on those little tires, were so fast. Very well done. Did you beat the camaro with the e36 body on it? Also, when was the last time you guys had times that close together? Maybe we can conclude the e82 is easier to hustle than the z4?

yep, the rear tires do not look anywhere close to the fronts. Rears look like they just went out for a drive around town.

This was also the first time my brother ran less than one second behind. So it probably means I need to learn how to drive the car to increase the gap or my brother just upped his driving big time without lettiing me know!

Thanks Satakal for the compliments! I was .02 seconds behind that monster e36, and .4 seconds faster than that driver I asked you about.