Tire size comparison
215/40R17 vs 215/45R17
215/45R17 is +3.6% taller than 215/40R17: 24.6 in vs 23.8 in (+0.85 in), and the same width. With 215/45R17 on a vehicle set up for 215/40R17, the speedometer shows 60 mph at an actual 62.1 mph. That is more than the ±3% difference many shops use as a rule of thumb, so check carefully before switching.
Set up for: going bigger (215/45R17 instead of 215/40R17) · Different situation?
Your current size
e.g. 265/70R17, 2657017 or 33x12.50R20
Where do I find my size?
It's on the tire sidewall, e.g. P265/70R17 115T, and on the tire placard sticker on the driver's door jamb (also in the owner's manual). The placard shows the size the vehicle came with; the sidewall shows what is fitted now. If they differ, use the placard as your starting point. Digits are enough here: 2657017 or 33125020.
Size you're considering
215/40R17 vs 215/45R17: full comparison
| 215/40R17 | 215/45R17 | Difference | |
|---|---|---|---|
| Overall diameter | 23.77 in | 24.62 in | +0.85 in (+3.6%) |
| Width | 8.46 in | 8.46 in | ±0.00 in (±0.0%) |
| Sidewall height | 3.39 in | 3.81 in | +0.42 in |
| Circumference | 74.7 in | 77.3 in | +2.7 in |
| Revs per mile (nominal) | 848 | 819 | −29 |
| Wheel diameter | 17 in | 17 in | ±0 in |
| Diameter in mm | 604 | 625 | +21 mm |
Speedometer difference
Your speedometer is calibrated for 215/40R17. Fitted with 215/45R17, the actual speed is the reading × 24.62 ÷ 23.77.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 20.7 mph | +0.7 mph |
| 30 mph | 31.1 mph | +1.1 mph |
| 45 mph | 46.6 mph | +1.6 mph |
| 55 mph | 57.0 mph | +2.0 mph |
| 60 mph | 62.1 mph | +2.1 mph |
| 70 mph | 72.5 mph | +2.5 mph |
| 80 mph | 82.8 mph | +2.8 mph |
Real tires: published diameters
215/40R17: 23.8–23.9 in published by 3 makers; 215/45R17: 24.4–24.9 in published by 7 makers. Calculated figures assume a nominal tire; the exact difference between two specific tires depends on their models.
More about each size: 215/40R17 · 215/45R17
Related comparisons
FAQ
Which is bigger, 215/40R17 or 215/45R17?
215/45R17 is +3.6% taller than 215/40R17: 24.6 in vs 23.8 in (+0.85 in).
How much will my speedometer be off with 215/45R17 instead of 215/40R17?
The speedometer is calibrated for 215/40R17. With 215/45R17 it shows 60 mph when you are doing 62.1 mph, and 70 mph at 72.5 mph (+3.6%). Your speedometer also has its own factory tolerance.
Can I replace 215/40R17 with 215/45R17?
The diameter difference is +3.6%. Whether it fits depends on things this calculation can't see: wheel width and offset, clearance at full lock and over bumps, load index and speed rating, and your vehicle maker's approval. Check your door-jamb placard and owner's manual and ask a tire professional.