How much taller is 275/60R20 than 275/55R20?

Five aspect points, and nothing else changes

These two codes differ by one field. The section stays at 275 mm, the rim stays at 20 in, and the middle number goes from 55 to 60. The result is 6.50 in of sidewall instead of 5.95 in, which is 1.08 in of extra overall diameter once both ends of the tire are counted. Section width is unchanged at 10.83 in — literally zero difference across the casing.

Where the inch goes

0.54 in of it lifts the axle. The other 0.54 in goes upward into arch clearance. Because the tire is no wider, nothing changes at the inner edge, at full lock, or along the frame — which makes this one of the few size steps whose consequences are confined to a single dimension.

The instrument change

3.39%, meaning an indicated 70 mph is 72.4 mph and 100 recorded miles are 103.4. As a rotation count the same change is 632.0 turns per mile falling to 611.3 — about twenty-one fewer. Modest, and worth knowing because this is a step frequently made without any recalibration at all.

What the taller one lands on

32.99 in is one hundredth of an inch under the 33.00 in of a genuine 33x12.50R20. So the practical description of this step is that it converts a 32-inch fitment into a 33-inch one while leaving the width and the wheel alone — the narrowest possible way to arrive at a 33 on a 20-inch rim.

Where the extra sidewall is felt

Going from 5.95 in to 6.50 in is a 9% increase in the amount of casing between the rim and the road. On a 20-inch wheel that is a meaningful proportion, because there was not much to begin with — the tire goes from 63% wheel to 61% wheel. Draw the two together and the outlines share a rim line and a width, separating only at the crown.