street

I've got 3 track days in a row and am wondering if my Sport Cups will make it. The wear bars aren't much help since the outer part of the tire gets most of the wear. The little "herring bones" on the outer tread of the tire are just barely visible. How much wear remains after the herring bones disappear? Thanks in advance.

Larry Harris

Track time is very destructive to any tire, as you now know. Take the car to a reputable tire shop and have them give you an educated guess.

38D

You can run them until they cords show, but they are no longer sticky past the tread pattern (the herringbone pattern you describe). If you are wearing out the outside first, then you should get some more negative camber. With a good alignment, you should be able to get at least 6 days out of a set, and probably more.

street

We had a DE during Parade and Michelin reps were at the track. They said that the herring bones are at the same depth as the wear bars and that MPSCs get "really good when the herring bones disappear." Just drop the air pressure a couple pounds or be ready for more sudden breakaway. Wish I knew that before. Pitched a "really good" set.

mooty

dont judge a tire merely by treads left. mpsc often heat cycle to death way before tread is gone. furthermore, i would not drive 2 year old mpsc that had some heat cycle on it way back. they jsut dont have the grip anymore.

and why would you take a chance with tire that may have "sudden breakaway"... i can and know how to deal with "intended" break aways when i over drive them, when i slide too much, when i enter turns too hot, but "sudden" breakaway is not fun to me.

LVDell

possible to exlpain what you mean by heat cycle to death? I thought heat cycling your tires was most important as a FIRST step to get them to have the best life and grip of the tire for subsequent sessions allowing the rubber to heat properly (not overheat or underheat). Are you saying that you "heat cycle" it everytime you have a track day with it? Guess I am confused on this one.

38D

The more heat cycles a tire has, the harder it gets. A heat cycle is anytime the tire heats up and then cools. This is especially true of slicks, which are only sticky for the first couple of heat cycles and then get worse and worse (of course they typically only last 10-12 HCs anyway...). I find that MPSCs are good for ~25 heat cycles, and slowly drop off. You can always use some Formula V to get them back.

LVDell

Ah....that makes more sense. So the FIRST heat cycle ( Article on MPSC Heat Cycle ) is the most important for prolonged life of the tire and then subsequent heat cycles are those that happen with every session you take the car out and then back in to cool waiting for the next session.

Am I on base yet?

multi21

You probably did the right thing throwing them out as they were at the end of their life expectancy anyway.

Mooty is right on the money with what he said. Regardless of tread depth, the MPSC have a tendancy to heat cycle to death before they go down to wear bars... or beyond

guykoken

38D:

What, pray tell, is Formula V?

Richard Bain

guykoken

38D:
I answered my own question by Googling Formula V. So now that I know what it is, I ask you: Does it work?

Richard Bain

mooty

sorry.
one type of heat cycle is to heat up tire, let it set for a while, say a week or two, then it's supposed to last a bit longer.

however, what i meant by heat cycle is that every time you are out on a "session", whether it's 15 min, 30 min or 45 min. once the tire is at operating temp and you then let it cool down (b/n sessions), that's ONE heat cycle. after 25 of those cycles, or thereabouts, the tire gets hardened and loses grip. yes, you can still drive on it, but you will notice the grip level falls off SIGNIFICANTLY.

so when evaluating tire life, you need to look at treads left, number of heat cycles, and how long the tires has been left sitting in the garage. and the importance of each factor differs b/n tires. slicks are usually very sensitive to heat cycles so is mpsc. toyo RA1 seems to be immune to heat cycle and you can drive to the cord without significant grip change, in this case, tread is the more important factor.

hope this helps.

mooty

oops, i just saw 38D beat me to it and gave similar explanations.

mooty

you got it!

however, opinion varies with regard to the usefulness of the FIRST heat cycle to increase tire life. for me, it made zero difference. for some it seems to work.

LVDell

Cool. Thanks all for the explanation.

....38D, what in the world is Formula V have to do with this thread? I too am stumped.