215/40R17 vs 235/40R17
235/40R17 is a safe swap for 215/40R17 by the usual ±3% rule: the diameter differs by +2.65%.
Speedometer and odometer
With 235/40R17 on a car calibrated for 215/40R17, the speedometer reads 58.5 mph when you're really doing 60, and the odometer under-counts by 2.6%.
| Speedo shows | Actual speed |
|---|---|
| 30 mph | 30.8 mph |
| 45 mph | 46.2 mph |
| 60 mph | 61.6 mph |
| 70 mph | 71.9 mph |
| 80 mph | 82.1 mph |
Other sizes close to 215/40R17
Questions
Can I replace 215/40R17 with 235/40R17?
235/40R17 is a safe swap for 215/40R17 by the usual ±3% rule: the diameter differs by +2.65%.
What's the difference between 215/40R17 and 235/40R17?
235/40R17 is 0.63" taller and 20 mm wider; the sidewall is +0.31". At an indicated 60 mph you'd actually be doing 61.6 mph.
Will 235/40R17 fit on 215/40R17 wheels?
Both use a 17" rim, so the wheel diameter matches; check the wheel's width range for a 235 mm tire and the fender clearance.