[2e9x's]

The Z1 Star Specs on my GTI failed pretty interestingly this weekend. Can you please take a look at the picture and tell me if you have seen failures like this before? They had about 7k miles, 1 auto-x, 1 track day (Auto Club Speedway roval) and a half auto-x day (the failure stopped the fun). Pressures were 29 psi cold.

Thanks!

[vwong]

I've seen those before, but not on Star Specs. I've had couple of Kumho V710 r-comps that had developed the type of failures you saw. I don't know why, but now seeing that your cold pressures were at 29psi, I'm wondering if it could be pressure related? I had about 24psi cold pressures in those Kumho V710, and they were on my Prelude.

I run Star Specs as well on my E92, but I set my tire pressures at 48psi front/40psi rear cold pressures for autox.

[satakal]

You didn't let Geoff drive the GTI did you? I'm so happy that failure didn't happen the weekend before.

[Outlaw 06]

Is that a front or rear tire that you pictured? It almost looks like a combination of over-inflation and cupping.

[S4to335]

I would contact the manufacturer...that aint right.

[Dascamel]

Originally Posted by S4to335

I would contact the manufacturer...that aint right.

+1


Did your tire get hotter than usual on any of the runs?

[2e9x's]

Thanks guys! Those are my two front tires. Both failed.

I contacted Dunlop and have asked for some help. Frankly there is no reason for them to have failed as they did in auto-x.

And no I did not let Geoff drive my car. That guy needs to teach me to drift...

[satakal]

Originally Posted by 2e9x's

Thanks guys! Those are my two front tires. Both failed.

I contacted Dunlop and have asked for some help. Frankly there is no reason for them to have failed as they did in auto-x.

And no I did not let Geoff drive my car. That guy needs to teach me to drift...

I've asked him to teach me but he's hesitant. I think he's trying to hog all the awesome. He wants it all to himself.

GL with dunlop. A hot pressure in the range of 37 doesn't seem too low to me. I've had similar stuff happen from 2nd gear drift/skid pad. The fast tires (bridgestone re01r) did something kinda similar. The slow tires (falken rt615) wore down like a good drift tire should.

[The HACK]

WTF...

http://www.e90post.com/forums/showthread.php?t=373319

I spoke up and criticized the driver in this thread...But if it's happening to you too...

[2e9x's]

A similar thing happened to Ken (the auto-x co-chair) on his 335i.

FWIW Dunlop agreed to warrant the tires with an offset for treadwear. As such they are giving me a 25% discount on a new set.

[kingkong954]

yup.. sure does look familiar

[aus]

Post on Bimmeforums track section.
Lots of racers there.
I was about to pull the trigger on these.

[DCP]

I have several similar but not as severe spots on the outside shoulder of my left front Dunlop from my most recent track weekend.

I wonder if someone could school me a bit on this topic. In this thread, it was suggested that the tire overheated from under inflation or from over inflation. Some at the track suggested that I ended up with too high a pressures. The damage was done on the last run on a very hot day. I generally understand that low pressure results in higher temperatures, at least on the road. I am having a hart time grasping how higher pressures could overheat a tire.

I certainly understand the overdriving part. I was pushing the hardest on my last run and I probably allowed slip angles to get excessive on a couple of the track's sweeping turns.

I also realize that alignment figures into this as well, but the part that confuses most is how I should be managing the tire pressures.

Thanks in advance.

[subieworx]

Wow, 29psi is really low for those tires. Most star spec sizes like to be mid to low 40's hot.

We have seen that a couple times on our race car (subaru) on these tires when they start at full tread depth and have been used hard and have many heat cylces.

[jgalaxy]

My Z1s up front suffer the same on the shoulders when overheated. I am sure they are squealing to you the whole time. I run 39 hot up front and 41 in the rear given my suspension setup.

[The HACK]

Originally Posted by DCP

I am having a hart time grasping how higher pressures could overheat a tire.

Lower pressure can overheat a tire because there's more movement in the sidewall and tread therefore generating more heat. Higher pressure can overheat a tire by creating a smaller contact patch, resulting in less grip and all the kinetic friction being converted to heat in a smaller, more concentrated area.

[chaz58]

well, the best thing to do is use a pyrometer and set your pressure accordingly. If you are at a track see if you can borrow one. Either too low or too high is going to cause a hot spot in the tire (high will be hot in the middle, low will be hot on the edges).

Originally Posted by DCP

I have several similar but not as severe spots on the outside shoulder of my left front Dunlop from my most recent track weekend.

I wonder if someone could school me a bit on this topic. In this thread, it was suggested that the tire overheated from under inflation or from over inflation. Some at the track suggested that I ended up with too high a pressures. The damage was done on the last run on a very hot day. I generally understand that low pressure results in higher temperatures, at least on the road. I am having a hart time grasping how higher pressures could overheat a tire.

I certainly understand the overdriving part. I was pushing the hardest on my last run and I probably allowed slip angles to get excessive on a couple of the track's sweeping turns.

I also realize that alignment figures into this as well, but the part that confuses most is how I should be managing the tire pressures.

Thanks in advance.

[chaz58]

As stated, 29 is way low for an autocross - especially the front of a FWD car. Your tread should roll over to the tip of the little triangles on the edge of the tread - your triangles are just gone...

It really does look like you over drove the tire, and the low tire pressure didn't help too much. Still, the star spec is an agressive tire and should be able to take a lot more abuse than, say, an all season tire. I don't see how a performance tire like this should chunk out like this given your tread depth. I have seen worse with people driving tires at full tread depth at the track - that is something you do not want to do.

ON a second look at the pictures - the side walls look like you might have simply worn through all of the tread and gotten down to the casing on the outer edges. The low PSI on an autocross could explain that too. I'm a bit surprised they did that in the center too. You are down to the tread wear bars though. Looking at the wear pattern across the tire, it looks like you may have been driving on them over-inflated at one of your track events?

Originally Posted by 2e9x's

The Z1 Star Specs on my GTI failed pretty interestingly this weekend. Can you please take a look at the picture and tell me if you have seen failures like this before? They had about 7k miles, 1 auto-x, 1 track day (Auto Club Speedway roval) and a half auto-x day (the failure stopped the fun). Pressures were 29 psi cold.

Thanks!

[aus]

I losing confidence on these tires. STALKER had a hell of a time getting two good front tires. He was getting vibration and a pull on the wheel through 2 sets of front tires.

[kenneth]

I am running 35 F / 36R cold with these tires. Hot they get to 44psi all 4 corners. All 4 tires (square) look pretty much the same, as I am running -2 camber rear and a little more up front. Couldn't be happier!