dbbarron

Running R7s on a dual driven race car (F-Stock Boxster S )

I'm assuming a Heata Cycle is demarc'd by a typical session.
However, If my co-driver and I run back to back, I assume that is still one HC.

What if we are separated by one 21minute session? Typically the tires don't cool down much in 20min.
Is that still 2 heat cycles?

alevine

Yes, I always look at one heat cycle per one session. I would guess that the tires cool down quite a bit in 15-20 minutes and the subsequent session will be considered another heat cycle. I can run my R7's up to 20-22 heat cycles depending on temps, wear, etc. but see a falloff after 15 or so cycles.

Veloce Raptor

Whether tires cool in 20 minutes entirely depends on ambient temp, track temp, and how and how fast driver number 1 drives.

dbbarron

Usually if the tire pressures are equalized (i.e., pressure has leveled off due to heat in tire and bled down to target; no more bleeding needed), over a 21 minute break between sessions we will only see a 2-3lb drop in pressure. The pressure is probably +10-12lbs due to heat. This suggest they are only cooling off say 25% from peak.

mark kibort

i dont know for sure, but one long heat cycle might equal multiple multiple heat cycles as heat drys and effects everything. I dont know for sure,but those that have done an enduro for 2 hours or more, how long have those tires lasted after that kind of use?

dbbarron

Perhaps longevity is a product of how much time at elevated temps under stress.
Thus, when people mention '25' heat cycles, they really mean 25 x 20min session= 500min at elevated temps under stress.

So, however you get to 500min, perhaps that's it.

mark kibort

yeah, I've wondered if that was true too, but here is the issue. no one that pushes the car to the limit of that platform seems to get more than 10 heat cycles on a set of R7s without huge degradation of speed...... this is hard for some to grasp, because everyone thinks they are going all out. but, all you need to do is take your car, vs your car in a real race running its fastest times and see where you are . for example, i can run 1:36 at laguna, but on bad tires can only hit the mid 1:38s on real bad tires, maybe 1:39s.. there are guys that run a car like mine and dont run faster than the 1:42-3s. so, in reality, I can run 1:42 for 25-50 heat cycles if this was my lap time goal . this is the same reason i was able to grab tires off a 1:31 car, after 3 heat cycles and be able to run my fastest time. the faster you go, the more heat you put in the tire, and the less it lasts, heat cycle and time. that's my theory anyway.