or maybe i wont widen the fronts, then do 18x8.5 with a 265/35 front then 18x9.5 with a 275/35 rear. what do you think of that?

 

Get the V1 spacers, lighter and with proper studs they are much stronger. I would replace all studs with ARP for track use anyhow. They will allow you to use up to 20mm spacers if you want. I have been running spacers on the track for 3 years now, all slip on style, no problems.

That would work , or you could bump up to 285 rear is you wanted.

Or widen the fronts to 10.5 and use a 20mm spacer and mount them in the rear.

 

v1s are stronger than the v2s?

thats an interesting option with putting the fronts on the rears, hmmm

 

V1 you have extended studs pressed into a steel hub, then a spacer and your wheel bolted on.
V2 you have studs pressed into a steel hub, then you bolt a thin aluminum hub to the steel hub, your wheel is now being held on by the studs that are in the aluminum hub that is bolted to the steel hub.

I like the steel hub idea, especially with high quality extended ARP studs. With my extended studs and long lugs i have over 20mm of threads engaged holding my wheel on.

 

ok, so its the fact that the wheel is bolted to the steel hub, vs bolted to an aluminum base basically?

 

Does anyone know by any chance, how a 285/40/18 will fit on a g35 coupe (with rolled fenders) with a 10.5 +15 ???

 

well, thats gonna be close, and will probably be determined by how much rear camber you have and how low you are. that setup will extend out 13mm more than what i have right now, in the pics a few posts back. my gut tells me you will be fine as long as you have a GOOD fender roll and dont mind a little bit of camber, but thats a guess

edit, on second thought, your tires will be 10mm wider (i have 275s in the rear) and the 10.5" wheel will make those 285s seem even wider. so, you might need to do some pulling to make it work, now that i think about it. let us know how it turns out if you go that route

 

When I use a tire size calculator, like the one here http://www.tiredepot.com/calc.html , when I compare the difference between a 255/40/18 to 285/35/18 in terms of ride height (circumference or radius), or aspect ratio difference, it tells me it will be a .1mm difference , and if i choose the same aspect ratio on the 255 and 285 it gives me a .5mm difference ?

 

Google Aspect ratio , read and learn.

 

Sorry I got the math wrong, thanks for your help.
The difference is aspect ratio between the 255/40 and 285/35 is 2.75mm
and the difference in aspect ratio between the 255/40 and 285/40 is 12mm. (If im correct) . Doesnt this mean im getting a more equal height with the 40/35 setup?

 

3.92" = 285/35 4.01" = 255/40 = .09" difference in ride height between front and rear

 

You don't want an equal height with this car. Stock it can with 225/45 and 245/45 the VDC/TCS and ABS is programmed to see a difference in tire height from front to rear to work properly. If your going to run a 285/35 rear , i highly suggest a 265 or 275/35 front.

 

yea, computer doesnt like seeing too much variation from stock. i put a switch to the yaw sensor power wire, so my vdc is completely disabled, but i still get an abs light sometimes because the variation between front to rear is quite different than what stock was. now i have 275/40/18 rear and 255/35/18 front. its too much.

 

255/40 - 285/35 = 204mm - 199.5mm = 4.5mm total (2.25mm above the wheel on the top and 2.25mm below the wheel on the bottom). That difference is 24mm total with the 285, or 12mm on each side like you said.

Yes, total sidewall on the 285/35 is ~7.9", or 3.9" on each side, and 8" (4" per side) for the 255/40. Therefore, the 285/35/18 is 25.85" tall, and the 255/40/18 is 26.0" tall. VDC may not like that, though it's only a minuscule amount.

 

K i just did all the calculations. I have a g35 coupe that came with the 19" rays and I measured their tire height to be
26.08" front and 26.71" rear
26.03" front and 26.66" rear [255/40 , 275/40]
25.02" front and 25.85" rear [255/35 , 285/35] - hankook rs3s

I previously had 20 inch rims (that i even used on the track a few times) which came to
26.75" front and 27.57" rear 245/35/20 n 275/35/20 -
I had no vdc issues and they worked fine, they werent even so bad at the track, expect for being heavy as crap. I had them on nitto 555 tires, which i was very satisfied with.

I really didnt want to use the 275/40 on the rear 10.5 +15, because I feel it gives that stretched look, And i want to run more rubber. a 285/40 gives me a ride height of 26.97" so .26" difference b/w stock.

Im just trying to theoretically figure out optimal tire combo with the rpf1s.

 

Hankook RS3 , the fast set up is 265/35 or 275/35 front and 285/35 rear. Either setup i just listed will have NO problems. If your suspension has a lot of understeer get the 275's up front, if not run the 265's.

BTW your over analizing the tire thing. All you have to look at is the difference between front to rear. If the tires would fit you could run a 39 inch tall tire up front and a 39.75 inch tall tire in the bad and have no VDC/TCS/ABS issues.