255/45-17 too weird?
 

Hey guys, curious about a weird fitment. Search strings are too short for "255" and "255/45" doesn't resolve because of the stupid slash.


Right now I'm sitting at stock height with some new Konig Ampliform 17x9 +40 wheels and my old 255/40-17 S-04s from my S2000. The wheel wells on the BRZ just look SOO big to me. I'll be dropping the car later on RCE Superstreet-1s (never had time to install during lockdown, go fig) but only enough to even out the gap around the tires. No crazy low for me.


Boost is in the very near future, so taller gearing is also a consideration- would 255/45 work out ok in terms of fitment in the wheel wells at +40 offset with a minimal drop? I don't see that size pop up much in the forums since 265/35 on 18s seems to be one of the favorite fitments. Alignments would be track functional but still street friendly (daily driver, HPDEs). This is about the only reference I could find, but maybe my Google-fu just blows, and I wouldn't be anywhere near that low:


https://www.ft86club.com/forums/show....php?p=2851950


The larger size would result in a 4% taller overall gearing, which would offset the 4.9% shorter gearing from the 4.3 diff, so that wouldn't be bad. The gearing on the 2017 just feels so short to me. I know tire selection gets a lot narrower in 255/45 vs 255/40, but Continental and Nitto seem to have some good offerings there.


Thoughts? Sell wheels and just go all in on 265/35-18? 255/40-18?

If you are going to boost then larger diameter tires are not an issue. Too large and you gear indicator will not indicated correct. Not a big deal just turn it off but for some reason I like it?

How much HP are you shooting for? 255, 265 tires are probably suited for over 400hp.

I ran 255/40R17 on 17x9 IIRC +35 offset with 4mm spacer for perfect fitment.
Stock is 24.6” diameter 255/40R17 is 25” diameter. That is probably the largest diameter especially on a 17 i would go both for performance, looks, and speedo not being too off.

If gap is too much why not lower the car a little more instead?

I don't have a gear indicator? I assume I can adjust ratios to get accurate speed/distance in an ECUTek program, is that right? Power target is 400 crank, which seems to be a good semi-agressive semi-safe number on 93 octane with an Edelbrock. We'll see.




Thanks for the data point! What were your alignment settings? So you were effectively at +31 offset... which means 275/40 will probably fit too on a +40 with a similar alignment, assuming enough clearance towards the center of the car.


I don't want to go very low- want more room for the suspension to work, maintain close to original geometry, plus clearance for daily driving. Plus to me the perfect stance is an even gap all around the tire, not zero clearance at the top of the fender and widening out as you go down.

I just found the spec it was 17x9 +45 with 4mm spacer in rear so effectively +41. +40 would probably be good too though. 17x8 +35 with 225 tire in front.

The rear does have a lot more clearance space than the front, I do think some people have successfully fit a 275/35R17 in the rear. However the main paint for clearance isn't the outside fender especially on stock ride height and you can add a little camber for clearance there if needed, and roll fenders etc... The main clearance point is the spring perch for inside wheel clearance. I think most people switched to coils because they are skinnier and allow for more clearance for the 275 tire, I believe on stock strut 255 is the widest you should run in rear.

I am almost positive you could fit the 255/45r17 in the rear you wanted initially however make sure you get equal diameter in the front. I believe that would be 225/50R17, being on stock ride height should also help fender clearance with that larger diameter, but you may need/want to run a slight amount of camber to be safe.

Got it. Thanks for your specs again!

I already run 255/40 up front at +40 with plenty of clearance, and was running +38 with no issues. I know +35 dropped with street camber seems to clear just fine. I'll be on coilovers, so I'm not worried about tire vs spring clearance. Guess I'll just have to go in and measure.

Are you running 265/40/17? Sorry to hijack thread, but i'm also looking to widen up. Will be running a bit north of 400 whp on e85 so need to prepare for it.

255/40 right now. I thought about 265/40 before on the S2k, but there really aren't many tires available in that size if at all for any given year. Your E85 target sounds like it scales right with my 93 octane gas target. :)