SidewallerTire & wheel calculators

255/70R18 vs 275/70R18

275/70R18 is 3.4% taller (+1.10 in) and 0.79 in wider than 255/70R18.

Caution
Check before you buy

275/70R18 is 3.4% taller than 255/70R18. It often still fits, but expect a noticeable speedometer error and check clearance at full steering lock.

255/70R18275/70R18Change
Diameter32.06″33.16″+1.10″+3.4%
Width10.04″10.83″+0.79″+7.8%
Sidewall7.03″7.58″+0.55″+7.8%
Circumference100.7″104.2″+3.5″+3.4%
Wheel18″18″Same
Revs per mile629608−21
SideTread
255/70R18275/70R18
Speedometer shows 60 mph62.1mph

Real speed on 275/70R18.

Ground clearance+0.55in

Change in height under the axle.

Width per side+0.39in

On the same wheel, split inboard and outboard.

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255/70R18 or 275/70R18?

Can I use 275/70R18 instead of 255/70R18?

275/70R18 is 3.4% taller than 255/70R18. 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 275/70R18 you are really doing 62.1 mph if the speedometer was set up for 255/70R18. Going the other way, 255/70R18 would make it read 58.0 mph at a real 60.

How much ground clearance does it change?

Half the diameter difference: +0.55 in (+14 mm) under the axle.

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