255/55R18 vs 255/70R15

255/70R15 is 0.0% taller (+0.01 in) and the same width than 255/55R18.

Same height

255/70R15 and 255/55R18 are the same overall diameter, so the speedometer stays accurate.

	255/55R18	255/70R15	Change
Diameter	29.04″	29.06″	+0.01″+0.0%
Width	10.04″	10.04″	0.00″0.0%
Sidewall	5.52″	7.03″	+1.51″+27.3%
Circumference	91.2″	91.3″	+0.0″+0.0%
Wheel	18″	15″	−3″
Revs per mile	694	694	−0

255/55R18255/70R15

Change sizes Speedometer table Gearing

Speedometer shows 60 mph60.0mph

Real speed on 255/70R15.

Ground clearance+0.01in

Change in height under the axle.

Width per side0.00in

On the same wheel, split inboard and outboard.

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255/55R18 or 255/70R15?

Can I use 255/70R15 instead of 255/55R18?

255/70R15 and 255/55R18 are the same overall diameter, so the speedometer stays accurate. 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 255/70R15 you are really doing 60.0 mph if the speedometer was set up for 255/55R18. Going the other way, 255/55R18 would make it read 60.0 mph at a real 60.

How much ground clearance does it change?

Half the diameter difference: +0.01 in (+0 mm) under the axle.

Other comparisons

255/55R18 vs 255/65R16 235/65R17 vs 255/55R18 225/60R18 vs 255/55R18 235/55R18 vs 255/55R18 255/55R18 vs 235/60R18 255/55R18 vs 235/65R18 255/55R18 vs 245/60R18 255/55R18 vs 255/60R18 225/55R18 vs 255/55R18 245/50R18 vs 255/55R18 255/50R19 vs 255/55R18 255/45R20 vs 255/55R18 255/55R18 vs 265/60R18 255/40R21 vs 255/55R18 215/75R15 vs 255/70R15 225/70R15 vs 255/70R15 225/75R15 vs 255/70R15 235/75R15 vs 255/70R15