Tire size comparison
225/45R19 vs 235/40R19
235/40R19 is −2.1% shorter than 225/45R19: 26.4 in vs 27.0 in (−0.57 in), and 0.4 in wider. With 235/40R19 on a vehicle set up for 225/45R19, the speedometer shows 60 mph at an actual 58.7 mph. That is within the ±3% difference many shops use as a rule of thumb (not a manufacturer or legal limit).
Set up for: checking a replacement size (235/40R19 instead of 225/45R19) · 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
225/45R19 vs 235/40R19: full comparison
| 225/45R19 | 235/40R19 | Difference | |
|---|---|---|---|
| Overall diameter | 26.97 in | 26.40 in | −0.57 in (−2.1%) |
| Width | 8.86 in | 9.25 in | +0.39 in (+4.4%) |
| Sidewall height | 3.99 in | 3.70 in | −0.29 in |
| Circumference | 84.7 in | 82.9 in | −1.8 in |
| Revs per mile (nominal) | 748 | 764 | +16 |
| Wheel diameter | 19 in | 19 in | ±0 in |
| Diameter in mm | 685 | 671 | −14 mm |
Speedometer difference
Your speedometer is calibrated for 225/45R19. Fitted with 235/40R19, the actual speed is the reading × 26.40 ÷ 26.97.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 19.6 mph | −0.4 mph |
| 30 mph | 29.4 mph | −0.6 mph |
| 45 mph | 44.0 mph | −1.0 mph |
| 55 mph | 53.8 mph | −1.2 mph |
| 60 mph | 58.7 mph | −1.3 mph |
| 70 mph | 68.5 mph | −1.5 mph |
| 80 mph | 78.3 mph | −1.7 mph |
Real tires: published diameters
225/45R19: 26.7–27.2 in published by 6 makers; 235/40R19: 26.1–26.5 in published by 6 makers. Calculated figures assume a nominal tire; the exact difference between two specific tires depends on their models.
More about each size: 225/45R19 · 235/40R19
Related comparisons
FAQ
Which is bigger, 225/45R19 or 235/40R19?
235/40R19 is −2.1% shorter than 225/45R19: 26.4 in vs 27.0 in (−0.57 in).
How much will my speedometer be off with 235/40R19 instead of 225/45R19?
The speedometer is calibrated for 225/45R19. With 235/40R19 it shows 60 mph when you are doing 58.7 mph, and 70 mph at 68.5 mph (−2.1%). Your speedometer also has its own factory tolerance.
Can I replace 225/45R19 with 235/40R19?
The diameter difference is −2.1%. 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.