SidewallerTire & wheel calculators

275/35R21 vs 275/40R20

275/40R20 is 0.3% taller (+0.08 in) and the same width than 275/35R21.

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Close match

275/40R20 is 0.3% taller than 275/35R21. That is inside the ±3% most shops treat as a straight swap.

275/35R21275/40R20Change
Diameter28.58″28.66″+0.08″+0.3%
Width10.83″10.83″0.00″0.0%
Sidewall3.79″4.33″+0.54″+14.3%
Circumference89.8″90.0″+0.3″+0.3%
Wheel21″20″−1″
Revs per mile706704−2
SideTread
275/35R21275/40R20
Speedometer shows 60 mph60.2mph

Real speed on 275/40R20.

Ground clearance+0.04in

Change in height under the axle.

Width per side0.00in

On the same wheel, split inboard and outboard.

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275/35R21 or 275/40R20?

Can I use 275/40R20 instead of 275/35R21?

275/40R20 is 0.3% taller than 275/35R21. 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 60.2 mph if the speedometer was set up for 275/35R21. Going the other way, 275/35R21 would make it read 59.8 mph at a real 60.

How much ground clearance does it change?

Half the diameter difference: +0.04 in (+1 mm) under the axle.

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