track wheels and tires

[The Radium King]

hi. looking to set up my old OEM 17" wheels for track-only duty. 7" front and 8.5" rear. questions ...

what is the widest folks are comfortably running on these things at the track? on my 8.5"/10" 18" wheels i am currently on 245/275 and was just as happy previously on 235/265. i think 235/265 would be a stretch (get it? get it?) on a 7"/8.5", but the internet tells me it has been done. otherwise 225/255 seems pretty standard.

tires? had my heart set on hoosier r7's, but the sizes are just not there. i need DOT to stay in my class, but want something more aggressive than an nt01. bf goodrich r1? toyo rr?

thanks for any advice.

[JayG]

225/255 is what I run on 17's 7" & 8.5"

RE-71s are a good choice for a DOT tire

[thstone]

Boxster Spec races with 235's on the front 7" wheel with no problems. On the rear, 255 is stock so you can probably go 275 on the 8.5" wheel but I'm not sure about clearance (maybe someone else can address that).

Toyo RR or R888 (R-copmpound) will be the fastest DOT tires.

[AZ986S]

I did exactly that. I powder coated a set of 17" Boxster twist wheel ( 7in F and 8.5 in R), and put Hankook R-S3 tires, 225/45s F and 255/40s R. I ran one complete DE on them. The R-S3s aren't the grippiest DOT tires, certainly not in the rain, but they are the value/price ratio is pretty good. They also talk to you very well and don't get too slick when hot. I figure even if I go through one set of them every year, that's not bad.

The 225s are already a little wider than I would want for the front 7in, but the 255s are fine for the Rear 8.5s.

[Topless]

Originally Posted by The Radium King

hi. looking to set up my old OEM 17" wheels for track-only duty. 7" front and 8.5" rear. questions ...

what is the widest folks are comfortably running on these things at the track? on my 8.5"/10" 18" wheels i am currently on 245/275 and was just as happy previously on 235/265. i think 235/265 would be a stretch (get it? get it?) on a 7"/8.5", but the internet tells me it has been done. otherwise 225/255 seems pretty standard.

tires? had my heart set on hoosier r7's, but the sizes are just not there. i need DOT to stay in my class, but want something more aggressive than an nt01. bf goodrich r1? toyo rr?

thanks for any advice.

If you are competing in Time Trials on (any) DOT-R compounds and want to win, you need to be on R7s in the widest tire you can legally run. Wheels are far less important compared to the contact patch in motorsport. If you really want to run OEM 17s (I always did) a 235/255 works well on stock wheels. You will have to give up the most competitive tire and run Toyo RR or Z214 instead. They are good DOT compounds but roughly 1 second slower than R7s in their prime HC. One second in Time Trials is a very long time if you have serious class competition.

Good luck!

[steved0x]

Price/longevity/grip is very good on the Hankook R-S3, for HPDE they are very good and are a blast, and they are very talkative. For timetrials with a 200tw limit, the RE-71R, the new Rival S, and the ZII star spec are faster at the cost of more rapid wear and reduced lifespan. An extreme example of this is a friend that runs autocross with Hoosiers estimated his tire cost in 2016 at $22 per 60-90 second run. If you want to win time trials in 200tw it is Rival S or RE-71R.

For HPDE I am all Hankook, but that is probably only because I have never run the RE-71R Another friend in a Cayman runs that tire, he like to slide around a lot, and he goes through 2-3 sets in the time it takes me to run through one set of R-S3.

[Topless]

Yes, choose your contact patch carefully based on your goals.

Competing for a championship, you want the best grip possible regardless of cost. That means a fresh set of R7s every track weekend in a DOT-R class at $1600. If you are running in a 200tw TT class you can have just as much fun and save a lot of cash with RE-71R. They will be good for 4-5 weekends and a set is around $900 installed.

Just DEs for kicks and grins? RS-3, AD-08, Direzza SS IIs, RE-11. All of these tires are viable track rubber that will hold up for 6-10 Track weekends depending on the driver and cost less than $900. A DE is non-competitive so forget chasing those GT3 Cup cars in your Boxster and just shoe up for fun.

[The Radium King]

thanks folks. I am building a nasa st-3 car to race with the regional association up here (a modified version of nasa pending full adoption) 20 minute sprints. I am allowed dot tires to 275 (to keep the weight and hp reasonable, anyway). I was trying to keep the initial entry cost down and run on the 17" for the first season (fire suits, transponders, fire suppression; all adds up quickly) but am finding tire sizing limited. I may put the 17's on my street car and move the 18s onto the race car.

regardless, good to know that a 235 works on the 7" front - balance is good with a 235/255 combo?

also, I've read good things about the bf Goodrich r1-s compared to the hoosier r7 - any experience with these?

thanks.

[Topless]

Originally Posted by The Radium King

thanks folks. I am building a nasa st-3 car to race with the regional association up here (a modified version of nasa pending full adoption) 20 minute sprints. I am allowed dot tires to 275 (to keep the weight and hp reasonable, anyway). I was trying to keep the initial entry cost down and run on the 17" for the first season (fire suits, transponders, fire suppression; all adds up quickly) but am finding tire sizing limited. I may put the 17's on my street car and move the 18s onto the race car.

regardless, good to know that a 235 works on the 7" front - balance is good with a 235/255 combo?
also, I've read good things about the bf Goodrich r1-s compared to the hoosier r7 - any experience with these?

thanks.

235/255- Yes, a slight sway adjustment may be warranted to fine-tune car balance

R1- Good grip, last longer, not quite as fast as prime HC R7s. (1 sec/lap??)

[thstone]

Originally Posted by The Radium King

regardless, good to know that a 235 works on the 7" front - balance is good with a 235/255 combo?

Yes, the wider front tire trims out some of the stock understeer for more balanced handling. Fine tune with adj sways and tire pressures.

[JayG]

235/45-17 will fit on a 7" wheel with Re-71's?
It doesn't squeeze it too much?

If so, Ill go that way as I probably have some points available

[thstone]

Originally Posted by JayG

235/45-17 will fit on a 7" wheel with Re-71's?
It doesn't squeeze it too much?

If so, Ill go that way as I probably have some points available

Yes. Spec Boxster runs Toyo RR 235/45/17 on the front 7" wheel. I can post a pic tomorrow.

[thstone]

Here are some pic's of the Boxster Spec tires and wheel sizes...

235/45/17 on 7" wheel:


Close up of sidewall of 235/45/17 on 7" wheel:


255/40/17 on 8.5" wheel: