Help a brother (944 Spec class) - need tire input

#1

Guys,

With the change back to RA-1’s and our 3 year rules freeze up this year, the 944 Spec series directors are considering changing our spec tire size from a 225/50/15, to a 205/50/15. This would bring us into line with SE30 & SM. One of our concerns is how the smaller tire would affect tire life. As you guys run the 205’s on a heavier, higher HP car, we thought you’d have good data on longetivity of the 205.

How many heat cycles are the fast guys getting out of their RA-1’s? Don’t need R-888 info (thank god they’re gone!). Thanks!

#2

I’m not anal enough to track heat cycles, but RA1s are good down to the cords, and if the car is set up right and the wear is even across the face, that takes awhile. I normally do maybe 8 race and 3 DE weekends a year on 2-3 sets. BTW our race weight is 2750 w/driver in case you weren’t sure, and the last time I checked corner weights, 54% of total weight was on the front wheels on my car with me in it. I’m guessing yours are more like 50/50 with the transaxle setup.

Disclaimer: I’m not one of the fast guys!

#3

Last year I did a lot of DE’s on RA1s, running hard laps while I worked on skills. Since they were DE’s I was running the tires right to the cords, which a guy would be less likely to do if he was doing more races then DE’s. 30 heat cycles was not remarkable. I wouldn’t say they were as fast towards the end, but they weren’t too bad.

#4

Sterling Doc wrote:

I’ll defer to IndyJim since you asked for “fast guys” but I think the pointy end of the grid could get more heat cycles out, but will take off their tires after a half dozen cycles if they feel them dropping off in grip.

Put another way: I don’t know any fast guys who run out of acceptable tread before grip. I don’t know any slow guys who run out of acceptable grip before tread.

Seems like the advantages to having the same tire size are numerous - the tire guy will always stock them. Slow guys can get take-offs from other classes.

Steve D.

#5

Hey Eric, I don’t think you will see much difference in the tire life between the 2 different sizes. I don’t think you will get a great answer asking here either as different people will get different amounts of heat cycles dependant on various different factors, starting tread depth, track, temp, driver skill, driver style, alignment, etc etc. Having said all that I get around 16 heat cycles with at least 4 of those being races. So a little over 2 weekends. Probably similiar to what you guys see on the 225. You will notice less grip going from a 225 to 205. I would think wear is probably slightly higher on the smaller tire but not enough to warrant not changing if its cost effective.

#6

Personally I’ve run the Nitto’s in the 225 and Toyos in 205’s. Not apples to apples, but I attribute any difference to the tire itself vs. the size. The Nittos and RA1s are fairly similar tires (I think even the same company? could be wrong?) so even the the time difference isn’t much.

Anyway I don’t think you’d see an noticeable negative difference going back to the 205’s. In fact the next set of Nittos I get will probably be 205’s since they’re cheaper.

As Steve (and others) pointed out I’ve haven’t corded a tire since DE days. This last set of Nittos I ran 3 enduros on so (3 hr, 2 hr, 2 hr) and they’re toast, but that is the closest I’ve come. Heat cycle way before tread.

My .2 cents.

#7

Hmmm

16 HC is what we were seeing out of the R-888’s, but we were typically seeing 25+ HC out of the RA-1’s. Usually would go an 8 race season on 1.5 sets, maybe 2 RA-1’s. Lots of data on this from Joe Paluch out in Arizona, who has tracked each set over about 8 years, and definitely a “fast guy” Most of the time, the rubber & HC ran out at about the same time. Maybe the extra tire helps prevent excess heat?

Thanks for all the replys, this is helpful

#8

What are you guys shaving the tires to start with?