ECS

I run about 8-10 DEs a year and am presently running a 997S on Pilot Sport 2s. These have had about 6 hours of hard track time. I always run in the instructor or advanced group. I have heard about heat cycles on R compounds and the performance trail-off. Anyone know about street tires? Thx.

weneversleep

Absolutely, heat cycles affect street tires, especially the more high-performance ones like your PS2s.

I just replaced a set of PS2s that I had done about 8 track days on, and it was amazing the grip of a fresh set compared to the old set.

Jim Michaels

This is a very good question, and an interesting first answer. I'd like to know more. Specifically, at what point should one consider new PS2s for street-tire autocross classes or tracking? If one goes this route in a serious way, I assume the new tires should be shaved, as new tread depths are at least 9/32s.

I usually run Michelin Cups for autocross (I know, I know) and track, but have autocrossed my PS2s five or six times in cooler weather, and also have 2 track days on them, with 16k total miles in almost two years. The rears still have about 5/32" tread depth, and the fronts about 7/32s. About how much quicker would new PS2s be for the start of next autocross season? Shaved versus unshaved? Just take a guess. I won't hold you to it.

JC3D

I ran the falken azenis 615 when I was on street tires. I would get about 3-4 weekends out of a set of them before they started wearing out from heat cycles. Usually still some tread on them at that point, but slides everywhere.

ECS

Thanks all for your comments. Sounds like street tires may also be affected. I would love to see some data on this question however.

Weneversleep; were you running 19" PS2s on an S?- my best times recently at Barber, with not-new PS2s, were achieved at 39lbs rear and 34lbs front hot. As they got to 43 and 36respectively my times got worse (ambient was probably about 10 degrees warmer however). Were your best tire pressures similar to mine.

Regarding heat cycles on street tires, I'll try to give tire rack a call and see if they have any thoughts and report back.

RonCT

I don't think there's much if any impact on street tires. I've run PS, PS2, PSC, RA1 on street and track. I've seen the drop-off with R-comps, but never with streets. I've been using PS2s as my rain / cold tires on the track since the tire was released -- probably 3-4 years ago at this point. Never an issue.

I remember reading something about this years ago and the formulation of the compound for street use is such that it's not really impacted by heat cycles -- and with street use you shouldn't be getting the tires hot enough to even qualify as a heat cycle. When I run my PS2s on the track, they certainly do get cycled -- but again, I've seen no issue.

It may be my imagination, so I'll keep an open mind...

TR6

I can't tell a difference with my Yokohama AVS ES100's. They suck before they are heat cycled and they suck just as bad after they are heat cycled.

Sean F

The experience that I had with Yoko AVS ES100's was that they did seem to heat cycle out and started really chunking

weneversleep

No, I don't (yet) own a Porsche. (but I want to soon...)

The tires that I was referring to above were Michelin PS2s on a 99 BMW M3, 17" staggered stock sizes. Grip in the last couple of track days was reduced noticeably. Changing tire pressures didn't seem to make a difference; the tires were just heat-cycled out (or so I think). This is not the first time that I've noticed street tires progressively losing grip once they have seen multiple track days.

In addition, I was getting severe chunking of the tire near their end, although I can't say whether this was due to the street tire going hard or due to my suspension changes.

I have yet to run a real R-compound tire, but obviously heat-cycling will affect R-compound tires more than a street tire. Still, we're still talking about rubber here, and it seems to me that heat-cycling would still have an effect on street tires, especially high-performance softer-compound street tires. I'm not a tire engineer, though, so I don't have any data to back this up other than my seat-of-the-pants feel.

--michael

ECS

OK, finally got around to calling Wheel Enhancement and Tire Rack with this question. Both people with whom I spoke said that street tires were pretty much immune to heat cycles. Two data points.

weneversleep

Interesting. Then again, we need to talk about what a "street tire" is.

Is a Bridgestone RE-01R, which is classified as a street tire but has a treadwear rating of 140, the same as some all-season tire? Or a PS2?

I wouldn't think that the majority of street tires are affected by heat cycling. But, high-performance street tires with low treadwear ratings (and, hence, softer rubber compounds) probably are. Not as much as true R-compound tires, but somewhat.

Again, I'm not a tire engineer, and I don't pretend to have more knowledge than people at Tire Rack or WE who deal with tires all day long. I just have enough engineering background to be dangerous...

mdrums

I ran PS2's all year and 11 track days at Sebring on 1 set. I went solo on my PS2's. they are amazing tires for the street and work well for guys like me at DE's. They really feel good and talk back really well.

I have only 1 day on my Toyo RA1's and they are full tread and seemed really squirley until I got the temps correct.

sjanes

Some R compounds don't heat cycle out, so I highly doubt a tire with a 140 tread wear rating would.

kurt M

From what I have seen and read chunking is more from gross overheat or excessive rollover and tearing of the tread blocks than compound(ed) heat cycling.