SidewallerTire & wheel calculators

255/55R18 vs 235/65R18

235/65R18 is 3.4% taller (+0.98 in) and 0.79 in narrower than 255/55R18.

Caution
Check before you buy

235/65R18 is 3.4% taller than 255/55R18. It often still fits, but expect a noticeable speedometer error and check clearance at full steering lock.

255/55R18235/65R18Change
Diameter29.04″30.03″+0.98″+3.4%
Width10.04″9.25″−0.79″−7.8%
Sidewall5.52″6.01″+0.49″+8.9%
Circumference91.2″94.3″+3.1″+3.4%
Wheel18″18″Same
Revs per mile694672−23
SideTread
255/55R18235/65R18
Speedometer shows 60 mph62.0mph

Real speed on 235/65R18.

Ground clearance+0.49in

Change in height under the axle.

Width per side−0.39in

On the same wheel, split inboard and outboard.

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255/55R18 or 235/65R18?

Can I use 235/65R18 instead of 255/55R18?

235/65R18 is 3.4% taller than 255/55R18. It often still fits, but expect a noticeable speedometer error and check clearance at full steering lock. Also match or beat the original load index and speed rating, and check that the wheel width suits the new tire.

Will my speedometer be off?

At an indicated 60 mph on 235/65R18 you are really doing 62.0 mph if the speedometer was set up for 255/55R18. Going the other way, 255/55R18 would make it read 58.0 mph at a real 60.

How much ground clearance does it change?

Half the diameter difference: +0.49 in (+13 mm) under the axle.

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