Like everyone else that has gone down the V8 route, I am having a wee bit of an issue with tyre choice.

The car is mainly used for track day sessions, full pace driving for about 15-20min sessions. At the moment a friend with a 1.6turbo is trying to convince me to go to 15x9 wheels with 225 tyres, but from what I can find 225 is the largest you can go in 15, so I am pretty convinced I should run with 17's and then the sky's the limit.

His argument is that the 17's will upset the handling of the car because of their larger rolling diameter, and that the suspension geometry will be all out of whack, and of course that the car can't be lowered as close to the ground, potentially effecting lift/drag/aero perfomance.

The other little argument that we are having, is over staggering the tyre size front and rear, if I go 17, was thinking about running 255/40 on the rear and 235/40 on the front to try and shift a little of the weight balance to the rear and of course get the power to the ground, front end grip hasn't really been a problem so far, it has been a struggle to stop the rear end wanting to pass me all the time. His argument is all the turbo miata guys run same tyre size front and rear, and have found that the fastest, I have tried to point out that my engine produces as much torque at 1500rpm as most of those guys do at full song, so it's kinda a bit different, and I can't go by what they run as much as he can.

So, anyone done any track time in their v8's and what tyre combo they run, does anyone know what Keith Tanner runs in his Targa car.

Rolling diameter for 225/45/15 is 22.95in, for 235/40/17 is 24.4in, and 255/40/17 is 24.92in.

Anyone any idea's comments, think I am a fool, and should just run with 15?

 

I thought about the same thing..... But 17 doesn't really look right on Na miata...

 

Nothing on my car has been done for look's but purely getting around the track as quick as possible. The guy in the GT3 isn't going to car what my car looks like when I pass him, just that a crappy old MX5 dusted him.

didn't think the 17" look all that bad.

 

alot better than I thought .... what offset are those ?
17" rims / tires are somewhat cheaper too

 

Wouldn't have a clue, bought them from a friend who had them on his MX5, he told me the offset, but it went in one ear and out the other.

 

I had 17s on mine and thought it looked out of place too. Though I do think the shot of the red car looks good. The problem with 17s is you can't get short enough tires to look right in the NAs. I'm running 15x9s and yeah 225s are much smaller than I would like but better than the 17s I had on it.

If you can afford it the best solution would be to have 2 sets of tires. There are plenty of options for race rubber for 15s that is wider than 225s. Like 275s on 9s
15x9 6UL GALLERY 3

The other thing is some tires tend to fill out the wheels better. The Rivals on mine don't very well
Jim and Jenna build diary, Miata LS1 Conversion: LS1 Miata 1st Road Test!

but NT01s do.
15x9 6UL GALLERY 1

Bottom line is we need someone to make a good street/track tire with a 140 tread life, great tread pattern and sized 255/40 15.

 

I already have two sets of tyre/wheels, and don't mind getting a 3rd different set if it is going to improve the laptimes, trick is that I can't find anything larger than 225 down here in NZ in a 15", no matter what tyre, but to be honest, haven't had a look at slicks, as a few of the track days they won't allow us to run them.

 

Something line NT01s would not be considered race rubber but you wouldn't want to run them on the street...

 

We all run either the Nitto NT01, Toyo R888, or Dunlop D03G's down here, they seem to be the best without going silly on price for a semi-slick.

 

I've been asking this same question for awhile now. My car is strictly a track car. Full cage, Fat Cat Bilstein Coilovers, Ford 331, so far 305hp to the wheels. I've used the following tire set ups. Tires have been Toyo RA1's (225-45-15) all around. Then switched to 888's. 235-50-15 rear and the 225's up front. Then pulled my front fenders to fit 235's all around. Past weekend I wore out my 235's up front and had my 225's with me so put them back up front. All in all they worked well.I do about 30-40 track days per year. I never time myself. I"m in the instructor & advanced group I'm mid pack. There are some very very fast race cars in my run groups.
If it were not for the cost, I'd go to the 275-35-15 Hoosiers. But, I do this just for pure fun and I cannot reconcile spending the $ the Hoosiers would run. I may switch to the Toyo RR for next year. From what I've read they are a stickier tire then the 888's. But biggest 15" size is the 225's. But, the dimensions of these 225's are barely smaller then the 888--235's. I've got the upcoming winter to figure this out.

 

I am considering going down to 16" from the 17" I am running at the moment, and putting 225's up front and running 245's on the rear on R888's, but I think we get the softer sticker tyre compound down here than what you guys do in the states for some reason.

My other concern is rolling diameter, the turbo guys all say that the only tyre to run is the 225 on a 15", due to it being about the same as the stock rolling diameter, where the set I am looking at are going to be over 1.5" more, and not sure whether this is going to stuff up the handling