ChuH

Stock IS-F
Front: 225/40R19 on 8" wide rim
Rear: 255/35R19 on 9" wide rim

What is the widest tire I can use on the stock IS-F rims? My dealer is considering buying back the stock tires so I can purchase wider ones.

I used a online tire size calculator http://www.powerdog.com/tiresize.cgi and I got the following.

Specification Sidewall Radius Diameter Circumference Revolutions Speedometer Odometer Difference
225/40-19 3.5" 13.0" 26.1" 82.0" 773/mi 60MPH 10000mi N/A
235/40-19 3.7" 13.2" 26.4" 82.9" 764/mi 59MPH 9881mi 1.2%
235/35-19 3.2" 12.7" 25.5" 80.0" 792/mi 61MPH 10240mi -2.3%
245/35-19 3.4" 12.9" 25.8" 80.9" 783/mi 61MPH 10130mi -1.3%

Specification Sidewall Radius Diameter Circumference Revolutions Speedometer Odometer Difference
255/35-19 3.5" 13.0" 26.0" 81.8" 775/mi 60MPH 10000mi N/A
265/35-19 3.7" 13.2" 26.3" 82.6" 767/mi 59MPH 9895mi 1.1%
265/30-19 3.1" 12.6" 25.3" 79.4" 798/mi 62MPH 10304mi -2.9%
275/30-19 3.2" 12.7" 25.5" 80.1" 791/mi 61MPH 10208mi -2.0%

Any suggestions? I don't like the current look of the narrow tires on the IS-F. I like the sidewalls to be straight vertical rather than to curve toward the tread. I don't want a buldging look either.

My thought is to go with 235/40R19 and 265/35R19. Of course this will increase the diameter which the speedometer will show slower.

Chu...

PureDrifter

iTrader: (10)

i suggest you get a different calculator, when was the last time u saw a tire with an 80" diameter on a CAR!

http://www.1010tires.com/TireSizeCal...?action=submit

mitsuguy

iTrader: (2)

it didn't format right - thats circumference....

I think I would stay as close to stock as possible, and do the 235/40 and 265/35's shorter wouldn't look good I don't think, and thats just a small amount taller...

Mr Johnson

I wouldn't do it for that small a change in tire size. I would do the 275 in the back and the 245 in front. But that's just me.

SoCalSC4

Pretty much any wider size you use will look goofy due to the narrow OE wheels.

Also, remember that putting an over-wide tire on an under-wide (for lack of a better term) wheel can actually decrease the performance characteristics of the tire. A 9" wheel is definitely on the narrow side for a 275 tire.

With the proper wheel widths and offsets, 255 front & 295 rear is possible on the IS-F with NO fender modifications.