Heatcycles ??????

[ottocycle]

Hello all,

 

I have been running a set of Hoosier A6 tires on my car for 2 seasons and noticed that they are feeling a little "greasey" during the last few trackdays I did. I am not experienced enough yet to know if this is me or the track (people commented on the track being a little greasy the last time I was out, 95 degree day). My local track is Summit Point and my car does not feel as planted as it should. I would like to believe I am driving harder and reaching my limits of adhesion but the stopwatch tells me different.

 

What I would like to know is this:

What constitutes a heatcycle? Is a 20 minute track session with 40 minutes downtime between runs a heatcycle or does a day of 4 or 5 20 minute sessions constitute a heatcycle?

I have at least 10 or more track days on my tires and bought them in April 2009. As my car weighs less than 1,400lbs on the track I still have plenty of meat on them, but I am wondering if they are heatcycled out. Depending on how it is calculated I have a minimum of 10 heatcycles or over 40 on my tires which are at least 18 months old.

While I am not obsessed about lap times I feel this "greasyness" or "skittishness" is a line not to be crossed and if its the tires I need to replace them. I would like to get the rest of the season out of them and wait till next spring for my new ones. I am considering changing from 14" rims to 13". Do tire softeners help?

When looking for replacement tires do some manufacturers have more heatcycles in their tires than others, and while I love the Hoosiers, they are expensive and if I am not going to wear them out perhaps I am better looking at a soft racing slick. I do not have to comply with any rules and regulations. Any recommendations?

 

I would appreciate the knowledge of people more experienced that I.

 

Thanks.

 

Dermot.

[Kitcat]

Maybe ask your tire supplier?

 

I had Hoosiers on my Miata and they ran out of grip before they ran out of rubber. Ditto my Kumos.

 

My Toyo RA1s just kept getting stronger so that's what I now run on my se7en. They don't have the ultimate grip of new Hoosiers but last much longer with no fall-off at the end. I have just abt worn all the tread off them-naturally shaved (after 10K miles and they shd be good for another 5K miles in the dry).

 

Remember to store the tires inside in the winter, below freezing weather is not good for race compounds.

[sdca7]

10 full track days is not bad for a set of A6's. Still much longer than most cars get out of them!

 

I'm trying discontinued racing slicks for a while - the Formula Continental and other Formula series use 13" wheels, so there are sometimes good deals on new but discontinued slicks. Good advice I got from a friend here is to find out the manufacture date of the tire before buying them, as they may have sat around for years and have degraded some.

 

I had to look at all the tire choices before choosing rim sizes for road courses. In order to accommodate the current selection of 13" Avons, Hoosiers, and still be able to use Formula Continental slicks, I went with 7" front and 9" rear. The fronts will be much narrower than a lot of folks use for autocrossing, but I think will be best for road courses.

 

Justin

[SkinnyG]

I ran a set of 13x9.5 Goodyear slicks for two full seasons of autocross (probably 35+ events, and two drivers). They actually went off in 15 runs. But I'm cheap, so I kept using them.

 

I bought a set of used 20.5x7 Hoosier slicks (couldn't get the 9.5's hot enough on asphalt) for $35/pr, and last event I soaked them overnight in 50% Xylene and 50% Toluene (I already have my kids, so I'm not worried about genetic mutation anymore) and they softened up pretty nice. Though I understand that once you use softeners, you always have to use softeners because they accelerate the aging process.

 

I've run Toyo RA1's in the past (on a different car), and I echo their awesome longevity. They grip and grip and grip and then they cord. They don't seem to age. Not as ultimate grippy, but an awesome dual-purpose tire.

[TheDingo8MyBaby]

If you're just doing track days, you may as well use tire treatment. Take the proper precautions...that stuff is nasty. Also check with your local track as some of them do not allow it.

 

Sometimes people just use WD40,saran wrap in a air tight black bag when storing tires.

[pureadrenalin]

Do not use softeners, not good for the tire, not good for you, and most tracks and all sanctioning bodies do not allow them.

 

A few words on the "greasiness" Hot track temps always bring oils, fuel, and past layers of rubber up, makes the track slippery. If you couple that with an alredy polished surface due to a large amount of useage..say..Road America, the track is really, really slippy.

 

Now, take a used tire that has probably hardened a little, and has been used past it's life expectancy. It's going to fall off quick and have little grip, leading to the loose/push issue you are getting. To go along with the loose/push type deal, you are probably overheating the tire a little or maybe a lot depending on severity, while pushing the car to go faster..it just makes it worse.

 

When you find yourself getting into these situations you have a few choices. Back off for a bit and let the slicks cool off a bit to let them regain their traction. Drop the pressures a bit so instead of overheating, you are just bringing them in to proper temp. Last, make sure you stay out of the clag, and try to avoid running wide. If you can afford to, get a seperate set of tires for transport between pit lane/paddock. It'll prevent you from getting a bunch of pickup on the tires which also leads to issues.

 

Lastly, avoid buying super inexpensive tires. You definetly need to buy tires that are quality. Hoosiers suck, period. You can get really good tires from the tire-rack starting at $100, shave some of those, and you get a really good tire for cheap.

 

Lastly, be aware that all slick or competition rated tires have a specific heat range that work best for them. Pay attention to what that is. Every manufacturer can provide you with a spec sheet, or information on what is best for that tire, including numer of laps that are reccomended. Utilising a street tire that is shaved for competition use will gain you some life, but the tradeoff is grip. It's up to you to find the balance. The other big thing is to work on a proper setup. If you have adjustable dampers, play with the rebound/damping and ride heights. Even adjusting camber +/- one degree can make a vast difference in handling. Pay attention to where you are loose and pushing in coners, and see what you can do to change things.

 

 

 

Sorry for the long winded response. And BTW, a heat cycle is bringing the tire from cold to operating temp to cold.

Edited August 23, 2010 by pureadrenalin

[Ian7]

As I interpret your description, you have 40 heat cycles on 18 month old tires.

I don't know the Hoosier A6's specifically, as we race on pure race slicks, but our tires are uncompetitive after a 4-cycle weekend. (yes four, not forty).

Tires lose grip potential long before they look "worn out".... :-)

[danilo]

Can't remember about race compounds on Auto tires (it was tooo long ago)

But with Moto race compounds, the makers (Real ones :-) claim approx 6 heat cycles and Max 3 months useable time.. whichever comes first. Yup VERY short life.

But then falling off a moto is far more serious than sliding across the parking lot.

Racing is V expensive... shouldn't be any news in that.

[WestTexasS2K]

Tires are probably cycled out. It's not unusual for tires on a 7 to be done with plenty of wear left. If they had been sitting on the shelf for two years the performance will be significantly decreased just from age alone.

[Mondo]

What about road tires? I have 7000 miles on 3yr old Falken 615s. Can't see much tread loss but they don't seem to stick like they used to.

Or, I've gotten used to them (and the car) and get near the edge of traction more often;)

[WestTexasS2K]

Same goes for road tires from my experience. I prefer to replace every two years.