184Best 255/40 R21 tires
40 rated tires available in this size, scored on dry, wet, snow, comfort and wear. Top overall right now is the Michelin Pilot Sport All Season 4 at 88/100.
29″
overall diameter
10″
section width
21″
rim diameter
694.7
revs per mile
Best 255/40 R21 summer tires
16184
283
382
487
580
679
779
877
977
1076
1176
4 more rated tires in this size are listed on their brand pages.
More top-rated 255/40 R21 tires
14
188
288
387
493
584
686
780
879
977
1077
1188
12922 more rated tires in this size are listed on their brand pages.
Best 255/40 R21 all-season tires
8
188
286
380
477
667
763
865Best 255/40 R21 winter tires
2
181
277Conversion
255/40 R21 in inches
| Overall diameter | 29″ |
| Section width | 10″ |
| Rim diameter | 21″ |
| Sidewall height | 102 mm |
| Circumference | 91.2″ |
| Revolutions per mile | 694.7 |
Wheels
What rims fit 255/40 R21 tires?
A tire fits a range of rim widths. Too narrow or too wide and the sidewall changes shape.
Minimum
7″
Ideal
8″
Maximum
9″
Rim diameter is fixed at 21″ — only the width varies. Estimated from the 10″ section width (70–90% rule).
Fitted from the factory on rims: 21x8.5, 21x9, 21x9.5, 21x10.
Popular comparisons
Sizes often compared with 255/40 R21
Close alternatives — each opens in the tire size calculator.
Sidewall
255/40 R21 — what does it mean?
| Parameter | Meaning |
|---|---|
| 255 | The first number is the section width — 255 mm, or about 10 inches across the widest part of the tire. |
| 40 | The second number is the aspect ratio: sidewall height as a percentage of width. At 40%, the sidewall is about 102 mm tall. |
| R21 | R means radial construction, which nearly all modern tires use. The number is the rim diameter in inches — this tire fits a 21-inch wheel. |