firelizard

iTrader: (1)

DISCLAIMER: This guide is not intended to help you fit wheels that don't fit. Its purpose is to list tires sizes of an appropriate width for a given wheel size while staying within an appropriate range of overall diameters.

WHAT IS A TIRE SIZE?

First number: section width in mm

Second number: height of the sidewall as a percentage of the section width

Third number: wheel diameter

18x8:
235/40-18
245/40-18

18x9:
235/40-18
245/40-18
255/35-18*

18x10:
245/40-18
255/35-18*
265/35-18

18x11:
265/35-18
275/35-18

--------------------------------------------------

19x9:
235/35-19
245/35-19
255/35-19

19x10:
245/35-19
255/35-19
265/35-19*

19x11:
255/35-19
265/35-19*
275/30-19
285/30-19

--------------------------------------------------

20x9:
225/35-20*
235/35-20
245/30-20

20x10:
245/30-20
255/30-20
265/30-20

20x11:
265/30-20
275/30-20*

*practical but incorrect diameter

WHY THO?

Because the 98-05 GS/Aristo was designed for a 25.3" (17" package) to 26.2" (16" package) overall tire diameter. The tire sizes listed more-or-less respect this criterion as well as the tire manufacturers' recommended wheel widths.

WHAT ABOUT 0.5" INCREMENTS?

0.5" is 12.2mm, I'm sure you can handle the math.

WILL IT FIT THO?

Maybe. Do your research on wheel sizes, ride heights, and fender modifications, literally every imaginable combination has been tried already and probably posted somewhere in this forum or on www.rimtuck.com

TrueGS300

Hopefully this will answer the weekly questions about what tire size to go with after changing rims

firelizard

iTrader: (1)

Nope, I guess it didn't help.

sbagdon

The only thing that would make this better would be a note for minimum offset, for each wheel diameter/width. When last under the car with the wheel on, the factory 17" rims were frighteningly close to the vertical arm on the hub carrier... like <10mm. Believe the factory 17x8's are either 45mm or 50mm offset, not sure what to do when going up inches, then also out inches, for offset.

tmf2004

iTrader: (15)

Great Post.. This should help others...

Blaque Diamond Wheels

GOOD POST! Thank you!

firelizard

iTrader: (1)

The topic of this thread is tire sizes, not wheel fitment. But I can touch on that briefly because it's fairly simple.
The wheel diameter doesn't make a difference because the tire is always going to be on the outside of the wheel, and the tire size determines the overall diameter and therefore the outside dimensions of the wheel and tire. The wheel only serves to locate the tire relative to the vehicle.
What will make a difference is the tire width, because a tire that bulges past the rim will give you less clearance than a square sidewall or a stretched tire.

Calculating equivalent offsets is easy enough though. Assuming the offset remains the same, every inch of extra width adds ~12.5mm to either side of the wheel. If you want to retain the same inner clearance, you decrease the offset by 12.5mm. If you want to retain the same outer clearance, you increase the offset by 12.5mm. If you go up by half inches, it's ~7.53mm.
So basically we only need one person to measure their clearance with a known wheel size and the rest can just be calculated. For example, since the stock 17x8 wheel has an offset of 45mm, a 17x9 wheel would need an offset of 32 to retain the same clearance to the inside.

Anecdotally, that matches up with my personal experience and yours. I have 18x9 +20 and that leaves me 20-25mm of clearance to the upright. I measured blindly without moving anything, so let's just split the difference and call it ~23mm. If my offset were 32, I'd have 12mm (32 minus 20) less clearance, just like the stock wheel. If you have ~10mm of clearance with the stock wheel compared to my, ~23mm, you can see how the math checks out (23 minus 10 = 13mm) even when just roughly estimating.

firelizard

iTrader: (1)

firelizard

iTrader: (1)

Bump. Can this get stickied or added to the FAQ. I searched for the title of this thread, word for word, and still had to go to the second page.

dreamcar88

iTrader: (1)

thank you, im assuming if i have an extra .5 like 8.5 and 9.5 i might be able to go up one more size in tire like 9.5 265 vrs 255

firelizard

iTrader: (1)

Every tire maker lists the min and max wheel widths for each size of each tire model.
If their official site is too crappy to make that easy to find, TireRack also lists this information for all the tires they carry.

OkiStash

On the note of 285/35/19(I know 285/30 was listed but I wanted some sidewall lol) on 11 in wide rims I keep seeing conflicting info. Some places say you'd need a 305 at minimal and a few Porsche forums saying 295 is gold. Can someone running 19x11 rears chime in?

firelizard

iTrader: (1)

as per my last email