255/40R21 tire size
A 255/40R21 tire stands 29.0 inches tall and 10.0 inches wide, with a 4.0-inch sidewall on a 21-inch rim.
- Overall height
- 29.0 in737 mm
- Section width
- 10.0 in255 mm
- Sidewall height
- 4.0 in102 mm
- Rim diameter
- 21 in533 mm
- Circumference
- 91.2 in2317 mm
- Revolutions per mile
- 695432 per km
- Inch size
- 29.0x10.0R21
Compare it with any other size in the tire size calculator.
Sizes you can swap to
These 21-inch sizes are within two width steps and 3% of a 255/40R21's overall height, the usual limit before the speedometer, ABS and transmission notice. The closest is 235/45R21, 1.0% taller (0.30 in). Wider sizes also need room in the wheel well and a rim width that suits them.
Plus and minus sizes
Changing rim size means changing the sidewall to keep the same overall height. On 19-inch or 20-inch or 22-inch rims, these are the closest matches to a 255/40R21.
Other 21-inch sizes near 255/40R21
255 mm wide, other sidewalls
40 series, other widths
See the other sizes for this rim on 21-inch tire sizes.
Shop 255/40R21 tires
These open each store's own list of 255/40R21 tires, where you can filter by type, load and speed rating.
255/40R21 questions
How tall is a 255/40R21 tire?
About 29.0 inches (737 mm) from the ground to the top of the tread, unloaded. On the vehicle, carrying weight, it sits a little lower.
What does 255/40R21 mean?
255 is the section width in millimetres (10.0 in). 40 means the sidewall is 40% of that width: 102 mm, or 4.0 in. R means radial construction, and 21 is the rim diameter in inches.
Can I use 265/40R21 instead of 255/40R21?
265/40R21 is 1.1% taller (0.31 in) and 10 mm wider, which is inside the usual 3% rule. With it fitted, the speedometer shows 60 mph when you are doing 60.7 mph. Make sure the extra width clears the suspension and fender liner at full lock.
What is 255/40R21 in inches?
In inch terms it is 29.0x10.0R21: 29.0 inches tall, 10.0 inches wide, for a 21-inch rim.
How many revolutions per mile does a 255/40R21 make?
About 695 turns per mile, worked out from its unloaded circumference of 91.2 inches. Makers list slightly higher numbers for their own tires, because a loaded tire rolls on a smaller radius.