safetyfastgt

Getting ready to buy some 2010 GT500 wheels. 18x9.5 with 45mm offset. Have Steeda Sports and Koni orange shocks with Steeda HD mounts. Can't decide if I want to go 255/45-18 all around or 275/40-18. Will be doing some autocrossing and general corner carving on mountain roads, so don't want staggered set up, plus want to be able to rotate. I know the GT500 runs the 255 up front but a 285 in the rear.

Whiskey11

You are going to get a lot of people's opinions on this matter usually the result of "this is what I'm running now".

So, on that note, I'm running Dunlop Direzza Z1 Sport Star Specs and they are kind of the jack of all trades tire. Good in the dry, Good in the Wet, relatively long tread life compared to other Extreme Summer Performance tires. They grip for days and are communicative at the limit. I'm on stock rims (18x8.5 Bullitts) and running 245/45/18 at all 4 corners. I have NO tramlining at -1.6º camber and neutral toe. That isn't much tire (especially not for a 9.5" wide rim). Only problem is that the 265/35/18 is far shorter than the stock tires are and there isn't a larger option (the 275's are only .3" taller at 25.6" with stock being 27.3").

Bridgestone has the RE-11 in 265/40/18 and 275/40/18 which are far closer (26.3 and 26.7 respectively) but they are expensive ($314 a tire).

Hankook RS-3, probably the best Summer street tire out right now has 265/40 (26.3" diameter).

The last popular choice is the Continental Extreme Contract DW (Dry Wet) has 285/40/18 (27" diameter) which is a great tire in the wet and good tire in the dry and has been getting awesome reviews and are about $1100 for 4 tires in 285/40/18. Not too shabby!

safetyfastgt

Thanks Whiskey, but I'm more focused on size now. I'm getting wheels from LRS and they sell Nitto and a discount with the package, so I'm trying the 555 for now.

Norm Peterson

Maybe this section-view comparison will help a little. On 9.5" wide rims, there really isn't a lot of difference. It's not exact, but close enough for purposes of illustration.

Assuming both sizes are the same tire make and model, the 255/45's might have a tiny bit sharper turn-in. But the 275/40's will probably hold up to the abuse longer before they get too slide-y, especially out on a big track.



Something else to consider is what sort of tire mfr support will continue to exist for either size in real performance rubber vs the "looks like performance" stuff.


FWIW, I currently have 255/45 Goodyear Asymmetrics (not the newer Asymmetric 2's) all around on the '08 GT500 wheels as my "3-season" setup. It's a pretty decent setup that seems to be toward the better side of true street tire (non-R, non-ST*) autocross performance, but I think there's room for improvement without dropping below 200 treadwear. Dunno, I *might* try NT05's in 275/40 next time around.


Norm

safetyfastgt

Interesting comparison Norm. Thanks. Not sure how to read the scale there. What do the numbers represent?

Norm Peterson

Inches, referenced to the ground for the vertical (where you can pick up the visible sidewall height) and to the wheel mounting plane for the horizontal (that way I can compare cases where the tires and the wheels are both different). The vertical centerlines are the midpoints of the wheel widths, which happen to be the same for this particular example.

Another sheet in that workbook (it's in Excel) will plot up approximately what the deformed tire shapes would be (you do have to tell it how much deflections are happening). It's not mathematically rigorous, but good enough for most discussion purposes.


Norm

safetyfastgt

Thanks Norm. Very useful info.