I go for 20 minute sessions and wanted to pick a tire currently running 17x9.5 et 38

I had 3 tires in mind

RS-3 - 255 - great tires
XS - 285 - also great tires, but i get 20mm more, but im worried it won't heat up fast enough.

 

if your car is NA 285mm wide tires are completely useless around a track.

Just get a set of a048, r888 or whatever decent semislick you can find. You'll be fine.

 

I've seen a lot of people that run 275 on the track.

Autox people run 295 to 285, but they run Hooisers, that have softer sidewalls that rollover compared to street tires.

R888 is a sticker compound so they should beat them even at 255, but I don't want to run them because the car is drive on the streets.

 

wut?

 

if they run 275 rubbers at the track then you know you can take every bit of advice they offer and flush it down the toilet.

 

There are a lot of online resources focusing on compound. I'd suggest you start there. For specific tire/wheel width that works for our car, this forum is a good resource; this is a subject that has been discussed extensively here.

FWIW, manypeople around here who do auto-x and/or track run 255s or 225s. I run 225s for road track duty.

 

you might be thinking 275/35-18

Hoosier released a new 275/35-17 size last year with a 24.7" OD

 

Hoosier isn't imported here as a brand... How am I supposed to know?

Anyway, with 190-220rwhp anything wider than a sticky 245 is a waste.

 

Any knowledgable tire engineer would instead say you are wasting forum bytes making such a statement

 

That would probably be true untill they went out and tested both configurations...

With 200rwhp how much rubber do you need to put the power down? How much a wider tire affects acceleration in the long run? How slow does turn in become? Is there a tangible grip advantage during long turns? How much does the car tend to understeer? Can it be corrected by adjusting the suspension setup?

My limited experience with wide tires on the rx8 made me choose 245\40 as an all around decent compromise between grip, handling and acceleration. That's all I know.

 

At least you finally admitted that your experience is limited. I was pretty sire that it was unlikely that you've fully tested every possible wheel width, tire width, tire compound, and tire construction.

To address your other assertion, why does peak engine output determine this? It doesn't. Adding more traction allows you to shift more load onto the powered tires and/or get on the gas sooner. If you can carry several more mph through a given turn you are a leg up on having to accelerate up to that same amount, which you would then also have to go faster still to make up the time it took to get there.

My only point is that the answer isn't as black & white as you've been trying to assert. We're not talking within the confines of a given series ruleset etc. it sort of reminds me when someone asserted there was no real advantage of changing to an aftermarket LSD ...

 

Nothing is fully black or white, ever. (Except for me, i'm as pale as you can get without glowing in the dark...) so you're right.

However the power output, together with other car features, generally determines how wide a tire has to be in order to let you be on the throttle as soon as possible. 245 was my sweet spot. You can't be on the throttle too soon anyway, a corner is a corner and understeer is always there waiting to steal some time. Anything more was a waste of weight and added friction which ultimately robbed me of the little power i had to play with. Wider tires where also harder to let slip while tring to slightly skid around tighter corners. This sucked, a little slip angle isn't always a bad thing.

With this in mind I also compared the lateral g charts on the same fast corners and saw no tangible increase in cornering speeds. The decision was rather simple to take at that point.

Now if I were to play in a very tight course i'd reconsider everything and probably come to different conclusions.

 

Be weary of buying a competition tire for non-competition use. I got some NT01s and used them at a rate of ~$2/mile with an effective life of <400 miles. IMHO, all seasons are the best, and cheapest, learning tool. After one day learning on the wide slip plateau of all seasons, I dropped 2s over a set of star specs. Craigslist is a great source for 25-50% worn all seasons, which are going to hold up better than new ones. Move to a Star Spec, RS-3, or RE11 equivalent to drop the times without killing the bank.