Tire wear

[enobiko]

I was at the NEOHIO Solo race this weekend, and had to stop early due to the cords showing on my passenger-side front. These are Michelin PS 4S, when doing autocross I bump up the pressure to 38 or 40, because they tend to roll onto the sides a bit. I run in GS, so I run a stiffer Eibach rear bar, and run zero toe front and rear, but stock everything else. I understand by loosening the front suspension bolts you can get a tiny smidgen of camber, and if I replace the struts I would certainly do so, but I wonder if it is worth the effort otherwise. (The top and bottom bolts are single-use torque-to-yield, I think...)
So... what would cause the wear in the attached photo? The tires are at the end of their life anyway, but... is this expected/normal? Did I push it too hard? (Yes, in a few places the front slid out.) The day was a bit hot, but nothing like you would see in Texas or Florida or whatever. Still, would spraying the tires with water have made a difference? Or, is it "You would expect this wear, given the circumstances"?
The rules in GS do not allow me to run camber plates, so don't go telling me to buy those, or go to coil-overs, etc, which would put me in a different class, where I think you have to run ALL the allowed mods to be competitive. Note also that this is a daily driver, so I don't want to go with track-day 200TW tires. I may wait until the Michelin PS S5 comes out, and see if they are any improvement over the PS 4S.

Dean

 

[jay745]

Seems like those tires are getting too hot because they're not meant for track use at all.

 

[enobiko]

??? "...not meant for track use at all."??? Apex uses the PS 4S on the Nurburgring, see the video here that explains the different tires they use:

They use it on the M3 Taxi, "about 2 tons fully loaded" with 4 people onboard. They get about 100 laps, and say they could get more.

 

[jay745]

Hey do whatever you want was just giving my opinion. Keep in mind the nurburgring is only about 10 mins a lap and not super hard on brakes. Most track sessions you're running 20-30 min sessions with more braking which put a ton more heat in the tires than a lap on the ring.

 

[khail19]

The fact that it only happened on one side makes me think it's an alignment issue. I would start there, I bet your toe is way off. That's a lot of wear for a single autocross session. Is the other front tire worn evenly?

 

[SierraCarrera]

You can get 200TW endurance tires that should last you longer and plenty of people also use them as dual-purpose summer tires. Hankook RS4, Conti Extreme Contact Force, Kumho V730s... but yeah would definitely look at alignment first.

 

[kep]

Like you said, there isn't much you can do while staying GS legal. A more temperature tolerant tire will be faster and last longer than PS4S and you may also be overdriving the car.

 

[enobiko]

The fact that it only happened on one side make me think it's an alignment issue. I would start there, I bet your toe is way off. That's a lot of wear for a single autocross session. Is the other front tire worn evenly?

Uh, no this was not a single autocross session, I've been doing Solo since 2019 (not all of that on these tires). The tires come off for the winter, but there are many miles on them. The other tires also have some wear on the outer shoulder, because... racing. But, all 4 tires were getting down to the wear markers, I intend to replace them next spring. I have not raced them on a full track (Nelson Ledges is nearby), my runs are usually around 50 seconds, so that would not heat up the tires as much as a full session on a road course.
Note: this is a 2017 SE with the Performance Pack diff, and I always turn off the ESC off (long hold).

 

[enobiko]

Like you said, there isn't much you can do while staying GS legal. A more temperature tolerant tire will be faster and last longer than PS4S and you may also be overdriving the car.

I agree... I may be overdriving the car. I'll try to pay attention to that in the future. Or, maybe I need a grippier tire to match what I *think* the car can do?? Then, I'd lose ride quality/noise, and also wet-weather traction. (It does rain in NE Ohio.) My best showing was an autocross that was very wet, which meant fewer drivers, but I think the tires helped me a lot. I got FTD!

 

[kep]

You want a tire that has a high heat tolerance and stiff sidewalls. The A052 is generally considered the grippiest 200tw, but would likely fair even worse than your current tires. SierraCerra had good suggestions.

 

[DarkArrow]

Funny how your post talks about driving in solo and not wanting 200TW tires for a daily, and immediately the discussion goes to PS4S aren't track tires and you need to buy 200TW tires.

From the sidewall wear, it looks like the tire is folding over a lot. My guess is the tires are underinflated for auto-x, you're overdriving and understeering, and you're putting in more steering input than needed because the brain naturally thinks "turn harder means car turns more", which only makes it worse and causes the car to slide even more on the shoulder of the tire. Add in you're driving a FWD car and now you have a sliding front tire on its shoulder trying to power out of a corner. All that heat going into that one strip outside shoulder tire results in overheating and chunking of the tread. But again, just a guess from your photo.

I don't know about the GTI, but my R's factory tire pressure recommendation is 39 psi. Given the GTI is slightly lighter, I'm guessing factory would be around 35 or maybe 37ish? Putting the tires at 38 or 40psi isn't really bumping up the pressures, and with PS4S already being well known as a soft sidewall tire, your tire pressures should be significantly higher for auto-x. I never got into competitive auto-x but when I did go it was on my daily tires as well. My tire pressures ended up almost always being closer to the max cold psi rating on the tire than my factory pressures to try and keep the tire from folding over.

I have no clue how experienced you are as a driver, so take this with a grain of salt. My recommendation is to get that tire pressure within a few PSI of the max cold PSI rating of your tires (whatever you replace these with) and try to slow down just a smidge and don't rely on a grippier tire to fix your understeering issues.

 

[Roald]

You asked what is causing it, but you already know the answer. They're old and have been beaten on with plenty of Autox events in an extremely camber challenged car. They're also still rolling over at those pressures. I think I recall my buddy saying the surface up there was pretty grippy? If so, you wouldn't have to overdrive much to get them to really roll and start chunking like this.
200tw tires are going to fair a bit better and wont chunk, but camber improvements and a fsb will add to that even more.
If you don't want to change class, at least get 200s suited for autox



I run in OVR / Columbus in STH. A year ago I was saying the same thing you are about going to STH. " you need a full build to be competitive " And while I'm sure this is true for other cars, the GTI is fully capable in STH with a f/rsb and good tires. It's also a GS ringer I feel. With just a fsb and good 200s- but you have to drive it right. And if you try to force it or overdrive you are definitely going to pay for it. The car is just too heavy.
A year into autox and I'm doing top 10 finishes in PAX and top 10's in ST, when we do classed events. I am only currently running a stage 1 tune, IC, f/rsb and 200 tw tires ( re71rs ). And most of my gain in time came from improving myself a lot, proper 200 tires and that FSB. I am NOT on coil overs or any camber equipment. I also have not aligned since I dropped my subframe, and still running mostly stock alignment . ( don't be me ).
We get enough dirt here in ohio that dropping the Subframe was easy peasy as we have built in witness marks as a result. - Anyways the point is the GTI is fully capable of Winning ST or GS, but it needs good 200tw tires.

 

[enobiko]

Thanks for the replies. Dark Arrow, your analysis seems correct, I was overdriving it in some places, and when I was trying harder I improved my time (from my first run) by only 0.3 seconds. I think I was faster in some places, but it must be that I was going too fast in other places, which slowed me back down. I can think of a few places where the front washed out big-time. I could be better...
I did a search on this forum to see what pressures people use, and I believe I saw 38/42 F/R. So, that's what I went with. But, I'm guessing that is with 200TW tires, which have stiffer sidewalls. I just checked, my max pressure is 50, so I could go up on pressure (but I'd probably shoot for mid-low 40's in the front). Stock pressure is 37psi.
Roald, I don't think I want to invest in a set of tires that I can only use for autocross, or suffer the compromised streetability trying to use them as dailies (NE Ohio roads can be bad).
You're right... worn tires and sloppy driving on my part... I can't really protest too much about a worn tire finally wearing out, given the circumstances. I may bump up the width a notch when I replace them next year.
Actually, I was first in GS by 0.59 seconds (over the only other entry in the class!) My PAX was right in the middle. I do this for fun, I'd like to do better, but I don't have any delusions that I'll be competing in Nationals or whatever. I need to improve my self, go faster by going only as fast as the car will allow. But, still having fun.
Also, you are running "IC"?? Does that stand for a larger InterCooler? Or ??

 

[krs]

Roald, I don't think I want to invest in a set of tires that I can only use for autocross, or suffer the compromised streetability trying to use them as dailies (NE Ohio roads can be bad).

I'd encourage you to think otherwise if you attend more than a few events a summer. You will save money in the long run, have better equipment for what you're doing, learn to be a better driver, be happier, among other things.

I'm not familiar with the rules for GS and wheel sizing. But a used set of rims and V730's would probably cost you about $1,100 not including mounting.

A052's seem to be the go to tire, but not if you're camber limited. They're also a lot pricier.

How much is a set of PS4S? Chewed up sooner than necessary?

A dedicated set was the best thing I did way back in 2008 when I first started autocross, and I have no intentions of going to nationals.

 

[enobiko]

The PS 4S is about $950 a set, the Kumho V730 is about $850 a set, stock size, without mounting/balancing. They are "not bad for a track day tire" as far as noise/harshness goes, but I bet my wife would notice. Plus... we have rain in NE Ohio, the PS 4S are known to be great in the rain. The V730 looks... like a track day tire, so it would be iffy on a rainy night. Maybe dangerous.
The A052's are about $1,050 per set. I like that you mentioned that I'm camber limited, and these tires are meant for a more extreme setup. Tire Rack did a test of a bunch of track day tires, but used an RWD car with camber plates. I don't know how much of that info applies to my car. Braking? Sure. Noise and harshness? Sure. Steering response and grip? Um... maybe, maybe not, the platforms are so different.
Oh, it's hard to tell how much wear I "should have" gotten on these tires. I have winter tires, and these summer tires, and this is my 2nd car with those tires, I don't know how many miles they have done, or how many autocross runs.