Oddjob

How far off pace of your qualifying time or best race lap are you by the end of a ½ hr Sprint Race? On R-comps, like Hoosier R6s, for something like a 2800-3100# PCA Stock E, F, G, H class car?

Accounting for changes in ambient/track conditions, traffic, and brain fade - I’m looking to get a feel for how much tire falloff would be considered normal, and how much might be indicating other issues (improper tire pressures, alignment problem, etc, ?).

I appreciate any insight and examples/experience,

FredC

Assuming the tires are still in the zone (ie still plenty of meat and heat cycles available) by the end of the 1/2 hour sprint, the delta should be negligible. If not, it may be a question of pressures shooting up due to over driving or set up deficiency. That's my 2 cents...

multi21

Too many variables. Summer temps from qualifying to the end of a sprint race later in the afternoon could be significant

Veloce Raptor

Agree 100%

M758

I agree, however every tire is different and some are more sensitive to sliding around. R888 are sensitive to going off during a race. I have had it happen. RA-1 are tolerant of this and even with a few lurid drifts the tire will come back in a lap at most if you settle down.

Driven properly with the right set-up the should be consistent.

Lemming

None if a fairly new set and a smooth driver (one exception might be when it's extremely hot).

Larry Herman

I have on occasion set my fastest laps at the end of an enduro on R6's. Probably a combination of not over-cooking the tires and the car getting light on fuel.

mikew968

I feel this is more driver related as I too have set my fastest lap at the end of the race.

bgiere

My fastest Mid-Ol lap ever was done on some Hoosier R6 that i had purchased in April of 2010. I was well aware that they were not optimum and drove very smoothly throught the entire race. No sliding, no drifting...halway throught the race they still felt terrific so i pushed a tad harder and they responded well...set a Mid-O lap record in my 944 during that race. If i had stickers on I may have over cooked it. Just my less than 2 cents.

Jim Child

+1

At the PCA Mid Ohio 90 minute enduro last year I set my fastest lap on lap 41 of 51. Lap 50 was only .2 seconds off of the fastest lap.

jrgordonsenior

It's very track and car dependent. A 911 based car will heat up the outside rear more than a 944 or Boxster especially with a wing and even more so on a banked track. I've had stickers that are gone berfore the end of a 30 minute race, and 5-6 HC'd tires that seem to last forever. I always try to find a lap or 2 where I can back of the tires and let them cool a little before the final laps to the finish line....

Sterling Doc

Tires like to live in a certain heat range. All the things listed above affect that - ambent temps, drving style, car layout, and balance, etc. One more thing that does is tire size. I tried getting away with Spec Miata sized Hoosiers (205) for one enduro, because the SM6 tire is cheap. Big mistake on a hot day - the little tires were cooked early on, and fell off in a big way. In contrast, I can run 245 Hoosiers hard for a long time, without them going away.

mark kibort

you should be able to match you fastest laps, as there are many factors in trade offs. your car is getting lighter with less fuel, track is getting covered with rubber, intensity of a battle, did you over cook and then stabilize by the end of the race (meaning sometimes the worse laps might be in the middle of the race), etc etc. generally, i feel the tires might go away in the middle of the race , especially in a heat of a battle, but even if that battle is at the end, you end up just dealing with the car with the tires that are "going off" and the same lap times just might be requrire more skill to achieve.

Van

I also regularly turn my fastest laps towards the end of races.

Oddjob

I started this post because I have been struggling with fading/slowing lap times since using R6’s, past 5-6 years. Maybe dropping off as much as 3 seconds between early fast laps and late in the race (3 mile lap, 1:50-1:55 range, around 95mph avg spd). If I dont get a clean run on the first or second lap of a qual session or race, forget it. Tires are already starting to drop off as early as lap 3 or 4. Feel greasy, start to squeal on turn-in and have to wait to get on the power to keep the back end in line. Have used both 245/16s and 245/285/18s, similar results. These are new tires for the race events, so stickers for the qual run, maybe a warmup. So 1 to 2 heat cycles going into the sprint race.

I dug up old lap times from club races going back to ‘99 to confirm what I remember - prior to R6s I used to have relatively consistent lap times start to finish using various tires: from SO3s & SO4s and BFG R1s, to burning up old Toyos and Yokos during Enduros.

Not sure what the issue is.

Tried a range of tire pressure w/ the R6s over the past few years, but still have not found the sweet spot. Typically run around 27-28 cold, 33-35 hot pressures. Have tried lower and higher which both seem worse.

What are you guys using/seeing for optimum temps at the end of a long session or race?

Other than tire temp/pressure - what kind of car setup parameters would you look at? Alignment specs and spring/damper balance, not much else (?).