SidewallerTire & wheel calculators

255/40R20 vs 275/40R20

275/40R20 is 2.2% taller (+0.63 in) and 0.79 in wider than 255/40R20.

OK
Close match

275/40R20 is 2.2% taller than 255/40R20. That is inside the ±3% most shops treat as a straight swap.

255/40R20275/40R20Change
Diameter28.03″28.66″+0.63″+2.2%
Width10.04″10.83″+0.79″+7.8%
Sidewall4.02″4.33″+0.31″+7.8%
Circumference88.1″90.0″+2.0″+2.2%
Wheel20″20″Same
Revs per mile719704−16
SideTread
255/40R20275/40R20
Speedometer shows 60 mph61.3mph

Real speed on 275/40R20.

Ground clearance+0.31in

Change in height under the axle.

Width per side+0.39in

On the same wheel, split inboard and outboard.

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255/40R20 or 275/40R20?

Can I use 275/40R20 instead of 255/40R20?

275/40R20 is 2.2% taller than 255/40R20. That is inside the ±3% most shops treat as a straight swap. 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 275/40R20 you are really doing 61.3 mph if the speedometer was set up for 255/40R20. Going the other way, 255/40R20 would make it read 58.7 mph at a real 60.

How much ground clearance does it change?

Half the diameter difference: +0.31 in (+8 mm) under the axle.

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