ProCoach

Scott, the tire rubber starts losing its elasticity as soon as it comes off the mold. I know competitive racers who search through a dealers stock to check date of manufacturing codes for the "youngest" tires.

My experience is the softer the tire, the more they degrade just sitting. I was working with a guy on slicks at Roebling last month and in my pre-event questionnaire, he stated that the tires on the car were "new." He could not get up to speed and the car looked terrible on video, as well as low numbers in lat and long G. I was tearing my hair out, then asked about the tires. Yes, they were "unused" but NOT "new." The date code was three years OLD!

We bolted on a new (purchased at the event, three months from manufactured date) set, he went out and dropped FIVE seconds a lap. Plus, he came back in grinning from ear to ear!

"The car's not trying to kill me, anymore." Honestly, I could have killed his crew..

Then, we got some good work done together...

mglobe

There are a LOT of people that need to read this IMHO!

Veloce Raptor

TRUTH

certz

^ Did they make their bus?

Coochas

I don't think a snowstorm is the proper place for a car do be doing yoga.

ir_fuel

Isn't it extremely complicated to correctly do the first heat-cycle on a tire on the racetrack, given the fact that it will be the first run for those tires (so what cold pressures to start with), and that no days are equal on track (temperature, number of participants, the track itself + which track you actually do this on). It seems to be nearly impossible to do this correctly.

And what do pro race teams do with their slicks? The ones used in a 24h race for instance?

Veloce Raptor

Pros will run both sticker slicks and lightly scrubbed heat cycled (on track) tires.

rrjohnson

How does shaving an RA-1 impact the need to heat cycle?

ProCoach

I think it's only hard to remain DISCIPLINED to do the first heat cycle properly on the race track.

The cold pressure and the variability of the track and environment is less important than the careful, controlled and uniform building of temperature TO the critical and recommended point (by the manufacturer) and then, NO more.

Most people do not achieve proper break-in by two methods.

One (and this is most prevalent in DE's) is that they never get to the target temperature (at least 160-165 degrees F across the width of the tire) ever. This is why the length of the break-in session is so variable. For a gentle driver, they may take all of a thirty minute session on a cooler track to get to 150 degrees F. For a quicker driver, they could get to 185-195 degrees F by the end of the out lap on a longer course, if they're not very disciplined... Most people, even in normal DE driving, rarely get to the NOMINAL 180-210 F (100 C) operating range recommended by a majority of tire manufacturers.

The second is usually my problem. I head out with the admonition of my tire dealer ringing in my ears (he's also my prep shop and transport/support guy) of GENTLY bringing them up to temp, NOT sliding the car around or locking up under braking and, most of all, BRINGING THE CAR IN after I get to the target temp (it's the sweet spot of grip, and unmistakable if your are very experienced in evaluating tires), not continuing to drive it "until it get's greasy."

If I ignore his advice, thus ruining the break-in procedure (and forever compromising the tire) by continuing to drive it past the "cure point," I begin to break down the bonds of the rubber's elasticity and run the risk of "hardening" the tire by extreme temperature and sliding. This also grains or tears the rubber so that there are thousands of tiny scallops on the tread face. The worse I abuse the tire, the fewer and deeper (more pronounced) those scallops are.

The tire might feel "as good as sex" until and for a short moment at that sweet spot of the target temp, but if I keep going, that tire will forever be compromised. THIS is the problem that I see most racers having.

Pros are a little different. You don't get to be a pro unless you have more than a little knowledge of how the thermo-chemical reaction is desirably obtained AND you can do it on a regular, consistent basis. THAT is the professional's discipline. Test day sessions, practice and even qualifying can be acceptable venues to do this.

The reason why, for endurance races, there are stickers put on the car in the race, is because they're not trying to "burn them down" upon exiting the pits. They bring the tire up to temp and back off a little, staying at or just below the sweet spot. The scuffs DO generally last longer, which is why so many teams use practice to do just that.

I did tire test for magazines a few years ago at the Michelin Laurens Proving Grounds. I was approved for using their 2-mile "High Speed" Test Track. My brief was simple, come up to speed as quickly as possible, do three hot laps within as narrow a time range as I could and supply subjective feedback on each set of tires. The measured temp when I came in with most sets was 220-230 degrees F after one out lap, three hot laps and in. My times varied by as little as half a tenth but never more than a tenth and a half.

For these tests, we did not care about durability or anything else, it was a pure performance measure. But the tires were DONE at the end. We remounted a few sets towards the end of the day and discovered that the times were not repeatable. We measured by durometer and confirmed that I'd "baked" them!

Tire tech is indeed, a "black art" but the information is out there to do it right.

ir_fuel

@rrjohnson:
I think both are separate things.
If you want more grip out of a fresh Michelin Cup they also suggest shaving it. I guess that's because the rubber on the outside is less "pure" (don't know how to call it exactly) than the one just below, but in both cases the heat cycling will give more life to the tyre.

BTW is there a topic here already about heat-cycling slicks? If I understand it right the best thing to do is to get a new set of slicks, run one heat cycle and then remove them from the car for at least 48h before using them again? Which means ideally you should always have 2 sets of wheels with slicks. The one with one heat-cyle, ready to be used and the one you are currently running on.

Will this heat cycling also help the enormous degradation a slick tyre has when it gets to the end of its life? I've seen cars run slower laptimes on used slicks than on used semi-slicks (same driver). It seems a slick degrades a lot more than a semi-slick, meaning that the grip delta between new and nearly EOL is a lot bigger than on say a Michelin Cup or a Pirelli Trofeo.

ProCoach

Shaving and hear-cycling are two different things.

Shaving reduces the tread block (on a treaded tire, even the A6 and R6) height and reduces the unsupported rubber allowing the heat to be dissipated more evenly and uniformly throughout the underlayment and carcass. Never heard of anyone shaving slicks (true, purpose-built racing tires). A tire cannot be shaved after it has been used. You would normally shave the tire before heat cycling (at least that's what I'd recommend) but I imagine you could order full-tread R-comps heat cycled. If anyone actually shaved a heat cycled, full tread tire before use, the benefit of that heat cycling would be negated.