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Tire Fitment II

Thanks to Buford. 


Paul Nimz told me his 225/60-16 fit with OE rims and did not rub. (in green)

He can make his 245/45-16 rub but only if he pushes very very hard. They are on 7.5" wide rims with 27 mm offset. They add 2.2 wider track to his SHO.  (in orange solid)

My 235/45-17 tires on 17x7.5" rims (45mm offset) never rub. They clear the struts by only .2" but never rub. (in red)

What we have are tires that define the limits in, out and up. By graphing I think we can find a safe zone. We also know that 235/45-16 on 16x7.5" rims (45 mm offset do NOT fit).

The factory 225/55-16 on factory rims with 42 mm offset are shown in (navy blue) for reference and never rub.


Inside (strut side)

Outside (lug nut side)


Paul's 245/45-16 tires stick out .709" more than mine & 245 tires should be on rims at least 8" wide. If we mounted 245/45 on 17"x8" rims we would get the (orange dashed line) which might clear everything if it had an offset some where in between. Mid way is 36 mm offset, +/- 2 mm ~ is  38 mm-34 mm offset. Because we know the strut will rub, I would error toward the low side, 32-34 mm offset.

This non-factory offset would also have a an effect on wheel bearing life and torque steer so try this at your own risk.

Your results may very, a larger tire on bigger rims will weigh more, and that is a bad thing. Exact tire dimensions vary by tire brands. But with all the group interest in 245 tires this is my best guess of how to do it. It is also true the farther a tire sticks out the more salt, tar and stones you fling on your own car.

The red rim is .618" further in, the orange rim 1.091" further out than stock. Add them together and with a custom rim with the correct magic offset and in theory a rim 1.709" wider than stock 6.5" wide rim could just work.  That eliminates 8.5" rims without custom body work ( 8.5-6.5= 2.0>1.7") They are only .3" too wide but we don't have that much room to play with. What you really want is a 8.0" with .3" clearance on the strut side. That is not too much clearance but it should work. Approved rims for 255 tires are 8.5"=10.0" so that will never happen (safely) without major modifications and/or rubbing. 

Another way to check what should work, 45 mm offset on a 7.5" rim. A .5" is 12.5 mm. Add .5" rim to get the 8" you don't want to be any closer to the strut so all that .5" needs to be offset. So 45 mm less 12.5 mm equals 32.5 mm offset MAXIMUM.  I would look for 32-30 mm offset 8" rims if I wanted 17x8" rims.

Just a few other thoughts. Paul's 245/45-17 side walls suck in .2" in section width because he is using a 7.5" rim which is .5" narrower than the standard 8.0" rim width. On the other hand the tread has more freedom to move about on a narrow rim than a wide one so it is possible for a tire to rub on 7.5" rims but not 8.0" wide rims. I stuffed Paul's car in a ramp or two with both of us beefy guys in the car and it never rubbed so I would take Paul's admission that he had to corner HARD to make his tires rub as an extreme and rare case.

The 225/60-16 effectively gears the car 3.5% taller, That would make an indicated 144 mph ~ 148.95 mph. Almost enough for the 150 mph club. A 235/55-17 is 27.18" tall for a 5.57% change.  That is good for an ego boosting "indicated" 152 but adjusting for speed error it is an actual 147.8 mph.    That is a bastard size but Tire Rack does list 2 Z rated or better tires in that size.

Shannon Burton was kind enough to drop a note to tell me his 235/40-17 tires do not rub using his 17x8" Volk AV3 rims but the tires are smaller than the red line and he could not provide an offset so I could not plot them and they would not add any new information even if I could.

Motor Trend reported Fittipaldi Polaris rims in 17x8.0 work, offset unknown. Tires were Goodyear Eagle GS-C 245/45ZR17.

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