I did some research and wasn't able to find a exact answer for my question. I currently have 255 40r18 on my 18x8.5 wheel. But it's hard to put down the power on the race track. So my question is, is it ok (safe) to run 265 or even 275 on 8.5 wheel? Thanks in advance.

 

I'm ran the OEM wheels a while back on my 08 and the rears were 18x8.5 w/+33mm offset and I ran a 275/40 tire with no problems whatsoever. My only reason for running a wider tire on that size wheel was to get a little buldge and have some more grip for auto-x.....

 

265 is the recommended maximum. While 275, 285 even 295 can fit on there for track and autocross use, it's not recommended for daily driving.


Your logic is flawed. Bulging sidewalls are softer than straight ones so handling can suffer. Squeezing a wide tire onto a small wheel actually lifts the edges up, causing less traction.

Yes, there are some tires that this works for but it may not be true for all "street" tires. BTW - I run 265s on 8" wheels for track and autox. Those tires and the proper pressures make them usable in that config but I wouldn't daily drive them that way.

 

265 max. Try new tires - that solves most of the "I don't have any grip" issues. It was remarkable what a fresh set of tires did for my high-HP Z32TT.

 

275/40 will work fine

 

^^ I'm assuming you are saying this size tire works fine on an 18x8.5" wheel.

What tire do you recommend, and what psi value?

--Spike

 

You say "race track" are we talking drag or corners?

 

Thanks everyone, great info!

I am trying to resolve my rear wheel traction problem on the race track by increasing my tire width instead of buying another set of wheels. In SCCA fourm, I have heard many different opinions about bulging sidewall decrease traction becoz of softer sidewall, but other drivers told me they actually gained some traction due to the increase tire width. However, I am still running on street tire. So you are saying that I will lose traction by fitting a 275 on a 8.5 wheel, right?

I have found that 28psi (cold pressure) works so much better than any higher psi. Possibly due to the weight of our car.

Corners

 

265 MAX and safe

 

A good 245 mm tire with out perform a mediocre 265 mm tire any day.

 

Corners race track. I dont know what that is?

 

Well, I am trying to compare the same tire, besides my tires are some of the top notch street tires in the market. However, i do not want to get into r-compound tires yet before I found the best combination of wheel size and width that fit my driving style. It s always harder to know the limit using those r tires.

 

So. . . what are your current "top notch" street tires, and what is their production date? (four digit code on the tire, starting with a 0)

 

Currently, I am running Goodyear F1 GS-D3, and i also tried the BF KDW2 and dunlop star spec, . I dont have a chance to look at the production date yet. I know you are actively been to the race track and is a experienced driver, what tire size r u currently running?

 

Both my autox set (Kumho V710) and my track set (Hoosier R3S05) are 275/40/17s all around, but I ran aggressive street tires for years before moving to these sticky tires. I've read very positive feedback on the Star Specs. KDW2s are mediocre, IMHO, and the GS-D3s are a decent street tire, but not fantastic (again my opinion).

If I had 4 8.5" wheels, I'd run 265s all around.

 

My fronts are 18x8.5 and I have 265s with no issues. Doesn't even look like its bulging at all.

 

I ran those tires on dry and wet surfaces. Overall its an impressive tire.

 

They are good street tires, but hella greasy on track. I was waiting and waiting for them to regain grip on corners.


By the way, thanks for all the info. I finally put the BS RE01R (265 35/18)on my 8.5 and they fit perfect. No bulging at all. However, every tires are different. My old Goodyear F1 GS-D3 were bulging even I fit 255 on my 8.5.

Anyway, handling problem solved. Car is so neutral with my re01r 265 35r18 square setup. Quick turn-in, tons of grips, I felt totally different than the previous setup!

 

I drift my z and go tho tires like crazy.
I remember I ran some (free) 295 on my stock wheel and it was crazy puffy lol.
It worked and was kinda hard to get on my wheel.

 

Re:> "...and was kinda hard to get on my wheel."

I'll bet it was "kinda hard" to get on your stock wheel.

It probably came off a lot easier though.

--Spike