Tire size comparison
225/50R15 vs 225/45R15
225/45R15 is −3.7% shorter than 225/50R15: 23.0 in vs 23.9 in (−0.89 in), and the same width. With 225/45R15 on a vehicle set up for 225/50R15, the speedometer shows 60 mph at an actual 57.8 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 smaller (225/45R15 instead of 225/50R15) · 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
225/50R15 vs 225/45R15: full comparison
| 225/50R15 | 225/45R15 | Difference | |
|---|---|---|---|
| Overall diameter | 23.86 in | 22.97 in | −0.89 in (−3.7%) |
| Width | 8.86 in | 8.86 in | ±0.00 in (±0.0%) |
| Sidewall height | 4.43 in | 3.99 in | −0.44 in |
| Circumference | 75.0 in | 72.2 in | −2.8 in |
| Revs per mile (nominal) | 845 | 878 | +33 |
| Wheel diameter | 15 in | 15 in | ±0 in |
| Diameter in mm | 606 | 584 | −22 mm |
Speedometer difference
Your speedometer is calibrated for 225/50R15. Fitted with 225/45R15, the actual speed is the reading × 22.97 ÷ 23.86.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 19.3 mph | −0.7 mph |
| 30 mph | 28.9 mph | −1.1 mph |
| 45 mph | 43.3 mph | −1.7 mph |
| 55 mph | 53.0 mph | −2.0 mph |
| 60 mph | 57.8 mph | −2.2 mph |
| 70 mph | 67.4 mph | −2.6 mph |
| 80 mph | 77.0 mph | −3.0 mph |
Real tires: published diameters
225/50R15: 23.9 in published by 1 maker; 225/45R15: 22.9–23 in published by 3 makers. Calculated figures assume a nominal tire; the exact difference between two specific tires depends on their models.
More about each size: 225/50R15 · 225/45R15
Related comparisons
FAQ
Which is bigger, 225/50R15 or 225/45R15?
225/45R15 is −3.7% shorter than 225/50R15: 23.0 in vs 23.9 in (−0.89 in).
How much will my speedometer be off with 225/45R15 instead of 225/50R15?
The speedometer is calibrated for 225/50R15. With 225/45R15 it shows 60 mph when you are doing 57.8 mph, and 70 mph at 67.4 mph (−3.7%). Your speedometer also has its own factory tolerance.
Can I replace 225/50R15 with 225/45R15?
The diameter difference is −3.7%. 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.