When to upgrade to R compound or race tires for auto-x?

[DarkBuddha]

This is a question that came up on a local board I'm on and it's been a very good discussion. Given that autocross, HPDE, track days, etc. are more and more popular among the pro-touring crowd, I thought I would pose the same question here:

When should one upgrade to an R compound or race compound/tread tires for autocross and other similar types of events?

I think it would be especially great to hear from the more experienced autocross drivers and their perspective on the value of running street compound tires versus DOT R compounds and slicks with regard to helping or hindering driver development as well as vehicle development.

Any thoughts?

[jeff s]

Race tires generally break loose more suddenly than street tires, at much higher cornering loads. The set up is different with sticky tires as well.
An inexperienced driver will learn more from using street tires for a while. IMO

[CamaroAJ]

for autocross we recommend to the noobs that they drive for the year on street tires to learn how to handle the car. then when they know what the car will do with the street tires if they want to upgrade then go for it.

r comps are normally 2-3 seconds faster on average that we see.

[Derek69SS]

I wouldn't ever run R-comps for an HPDE (unless I had a worn set I wanted to finish off), since those aren't competitive events, R-comps are expensive, and they wear quickly.

For autocross, I'd say when it becomes a requirement to be competitive in your class... I'm one of 4 guys that run C-Prepared locally, and we all run overweight underpowered cars on 17x9s with street tires. I can be competitive in my class without R-comps, by improving my driving (I won the last event by 2 tenths, and lost a few events by less than that...) If I had R-comps, I could beat them by 1.5-2 seconds, while driving sloppy... where's the fun in that?

My next car will be a stripped down lightweight class prepped Camaro, where I'll choose an index-class to run in using the RTP/PAX system to run against the top local people in other classes. I can choose "Pro" class and run it on slicks, or the "Street Tire Index" class to run it on street tires. I'll probably run "Street Tire" for a year to work the kinks out of the car, then run "Pro" so I can tune the suspension around slicks in an effort to be somewhat competitive at Nationals.



r comps are normally 2-3 seconds faster on average that we see.

Rick Ruth's street-tire conversion factor shows an R-compound to run 0.975 the time as an equal sized competitive street tire (Where a street tire runs 60-sec, an R-comp would run 58.5). Obviously, this will vary depending on a lot of factors (surface, temperature, car weight & HP, etc...) but it's what many SCCA clubs are using for their "Driver of the Year" calculations.

[DarkBuddha]

Good discussion points so far. It does kinda seem like an obtuse question initially... who wouldn't wanna run R comps, right? But you guys have brought up some excellent points, especially regarding driver development versus car development/setup.

Even in my meager experience, I've already had to deal with the issue from a couple different perspectives. For example:

I've always kinda ignored standard classing and PAX stuff, but recently I've found myself fall further and further down the results list against cars I think I should be competitive with regardless of classing. I started to wonder why and realized most of those cars are running on R comps or slicks, so I've lost one of my metrics for how I'm doing as driver because I've chosen to stay with street tires. Sometimes I do wonder how a 400hp M3 would do on 400 tread rated all seasons versus Hoosier A6s, and how I'd do on A6s versus hard-as-rock all seasons. But I always come back to the same thing... I still need to do better as a driver, so it doesn't matter that the other guy is on R comps or not.

On the other hand, I've also found that with my XR4TI I may need to get stickier tires to handle its weight and how it makes power. For example, it's tough to fit much more than a 215mm width tire in the stock wheelwells with stock style strut suspension. Add to the equation that the car weighs in close to 3400 lbs (wet and with driver) and makes light-switch kinda power (on or off), and both lateral and linear traction can be an issue on such small tires. This is where car development comes in... what to do? One answer is to convert to coilovers and trim/push/cut the fenders. Another is to run a stickier compound in the same tread width. Not necessarily an easy decision.