Tire graining??

[M43S7RO]

I went out to my second hpde at Arizona Motorsports Park and went well until the last of 5 sessions, ambient temps were mid 80s. I felt the front end get noticeably slippery about 3 laps into the session which I had not felt in any of the other sessions. I wound up having to back off considerably for the remainder of the session. I've read that re71s tend to get slippery so hadnt given it much thought but reflecting on a pic I grabbed of the tires after I got home, it seems to me that the tires are grained pretty good. It makes sense that this rolled rubber would be similar to rolling around on marbles and probably contributed to the loss of grip up front.

From what I've read, graining can be caused by pushing too hard before the tire is up to temp. I was taking it easy first lap to warm the car up and started pushing second lap in, relatively speaking (remember, noob on track here).

Looking for input from the experienced folks here for confirmation of whats going on here and practice to avoid it? I'm thinking more warm up laps and then a push lap or two followed by cool down laps, then push lap again if that makes sense?

After the first lap, I was pretty much pushing the tires for the full 20 min... trying to learn what getting closer to the limits feel like.

[dparm]

It's called "ricing" and it's somewhat normal if you're working the tires hard. What were your starting and ending pressures? How hot was the track surface? How much slip angle do you typically drive with?

[kyippee]

I'm just impressed by how even the wear looks. Didn't wear just the outside edge and the center line looks quite even. Wow

[Bimmer Barney]

Yes this is caused by over heating the tires which can be caused by improper air pressure or just simply over working the tire. It's very common and some graining is normal after a track session. The bigger chunks are just rubber you picked up from the track and will be gone after a bit of road driving and the graining/ricing/tearing on the contact patch will smooth out too, but the furtherest shoulders will remain.

That wear pattern is very common so wouldn't be overly concerned but dial in your pressures to improve the consistency of grip on track.

On the side wall there is a little arrow. The tip of that indicates the limit of useable tread. In the photo you haven't hit that yet which means the tire isn't flexing as much as it could to give more lateral grip. I would say you could drop some air pressure and then see how close you get to hitting that arrow point. Drop in 2 psi increments when dialing it in.

There are lots of ideas about tire pressures, but that's how I do it and it works for me. On my car it's a little Goodyear Shoe. Notice the wear feathers right down to the top of the shoe.



As for tips: street tires should be plenty warm after a lap and a half at a 70% pace. You're correct about throwing in a cool down lap. That makes a huge difference. I can pretty munch guarantee those bigger chunks weren't stuck on your tires while you were lapping unless you were out in no mans land off the racing line. What is more common is on the final lap you were not staying on the racing line and then you came across the track into pit entry and picked up some "marbles" on very hot and sticky tires. The greasy feeling could have been the track too. 80 ambient was probably 100 track temp. I wouldn't think that would make it too greasy, but just remember the track temp is always quite a bit higher. I used to race motorcycles in late spring at Chuckwalla. We had some ambient 100* race days and the track temp was about 130*. Imagine the tire temps after a race!

[M43S7RO]

I was taking tire pressure after coming off track, think my last measured was 34 hot up front. I did not take a reading after last session, again because I didnt think much of the slippery tires at the time and was packing up.

Dont have track surface temps & no slip angle before the slippery phase. I was not driving hard enough into the corners to require more steering input than I was getting. Once the tires got slippery then at that point I would have needed more steering angle but I backed off because the feeling was different.

Originally Posted by dparm

It's called "ricing" and it's somewhat normal if you're working the tires hard. What were your starting and ending pressures? How hot was the track surface? How much slip angle do you typically drive with?

[M43S7RO]

Great feedback, ty! Had no idea about the triangles and meaning, looks like I have a little ways to go. This is also the inside tire running ccw, I'll have to check other for kicks. I am being conservative in exploring limits. Safety and the car as I arrived in the morning is priority.

Originally Posted by Bimmer Barney

Yes this is caused by over heating the tires which can be caused by improper air pressure or just simply over working the tire. It's very common and some graining is normal after a track session. The bigger chunks are just rubber you picked up from the track and will be gone after a bit of road driving and the graining/ricing/tearing on the contact patch will smooth out too, but the furtherest shoulders will remain.

That wear pattern is very common so wouldn't be overly concerned but dial in your pressures to improve the consistency of grip on track.

On the side wall there is a little arrow. The tip of that indicates the limit of useable tread. In the photo you haven't hit that yet which means the tire isn't flexing as much as it could to give more lateral grip. I would say you could drop some air pressure and then see how close you get to hitting that arrow point. Drop in 2 psi increments when dialing it in.

There are lots of ideas about tire pressures, but that's how I do it and it works for me. On my car it's a little Goodyear Shoe. Notice the wear feathers right down to the top of the shoe.



As for tips: street tires should be plenty warm after a lap and a half at a 70% pace. You're correct about throwing in a cool down lap. That makes a huge difference. I can pretty munch guarantee those bigger chunks weren't stuck on your tires while you were lapping unless you were out in no mans land off the racing line. What is more common is on the final lap you were not staying on the racing line and then you came across the track into pit entry and picked up some "marbles" on very hot and sticky tires. The greasy feeling could have been the track too. 80 ambient was probably 100 track temp. I wouldn't think that would make it too greasy, but just remember the track temp is always quite a bit higher. I used to race motorcycles in late spring at Chuckwalla. We had some ambient 100* race days and the track temp was about 130*. Imagine the tire temps after a race!

[sc_tr0jan_m3]

Based on the pic you shared. That ain't graining. That's just rubber being moved around and you're also picking up rubber from other people's tires (aka OPR, other people's rubber).

What you shared is totally normal and what you experienced about the re71r's rather normal too once you start pushing the car.

It doesn't sound like you're overworking the tire esp if it's only your second time on track. Keep tracking tire psi as you come off track and feel free to test and experiment and see what changes… also keep using the first lap or two to warm up the tires and you'll be money.

[roastbeef]

just watched an interesting vid on the subject. apparently its from pushing a cold tire too soon.

[bbnks2]

re-71r is a soft tire that heats up quick. Looks pretty normal for the compound.

[M43S7RO]

As an avid follower of F1, I enjoy this guys videos. I hear graining come up frequently during race broadcasts but a little unclear of what it looks like hence my question.

When you have 20 min to run and ~2.00 min laps = about 10 laps of running. Factoring in a warm up lap or maybe 2 to bring the tires up to temp and working cool down laps into the mix & traffic... the number of clean flying laps you get becomes small.

Originally Posted by roastbeef

just watched an interesting vid on the subject. apparently its from pushing a cold tire too soon.

[roastbeef]

I'm not sure it's graining. Tires get boogers (technical term) when pushed. It's like a pencil eraser- push it one direction long enough it's going to get a little tail on it.

[dparm]

Originally Posted by M43S7RO

I was not driving hard enough into the corners to require more steering input than I was getting. Once the tires got slippery then at that point I would have needed more steering angle but I backed off because the feeling was different.

Maybe we need to ground ourselves on a common vernacular. Were the fronts sliding or the rears? You're talking about needing more steering angle and sliding...

[dparm]

The term is "compound shift", I believe. The combination of hot, soft rubber and tires sliding means you are literally pushing the rubber laterally. It later cools and you see those weird shavings.

I do see some ricing on there too, which is merely a sign of the tire getting hot.



OP, I don't see anything to be concerned about. You drive to the traction you have. Sometimes it's hot and the tires get greasy, so you learn to adjust your inputs accordingly. I don't think there's anything inherently wrong with the tire or the car. I agree that lower pressures might help, as you aren't wearing it down to those triangles on the sidewall.

[M43S7RO]

Front began to slide a few laps into the last session. At this point I slowed down, I didnt see the point in trying to keep the same pace in the corners if the tires were sliding.

Judging from responses that the wear looks normal, it seems it may have been re71r nature or high psi which I didnt read when done.

Originally Posted by dparm

Maybe we need to ground ourselves on a common vernacular. Were the fronts sliding or the rears? You're talking about needing more steering angle and sliding...

Originally Posted by dparm

Sometimes it's hot and the tires get greasy, so you learn to adjust your inputs accordingly.

Ok, this what I'll need to adjust to. First time I felt this and my cautious reaction was just to slow down.

[dparm]

So it was understeering. Your instincts were correct to slow down a little bit, the front tires just didn't have enough grip. Slightly lower pressures would've helped too. Give yourself more credit -- recognizing the change in grip and immediately knowing what to do is a sign of skill.

The RE71R can take the heat, but as you get faster you will probably find them a limiting factor and decide to move up to something like a Hoosier.

[Grillpt]

He's on his second day.. RE71 is already plenty of tire