Tire size comparison
245/40R19 vs 255/35R19
255/35R19 is −2.6% shorter than 245/40R19: 26.0 in vs 26.7 in (−0.69 in), and 0.4 in wider. With 255/35R19 on a vehicle set up for 245/40R19, the speedometer shows 60 mph at an actual 58.5 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 (255/35R19 instead of 245/40R19) · 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
245/40R19 vs 255/35R19: full comparison
| 245/40R19 | 255/35R19 | Difference | |
|---|---|---|---|
| Overall diameter | 26.72 in | 26.03 in | −0.69 in (−2.6%) |
| Width | 9.65 in | 10.04 in | +0.39 in (+4.1%) |
| Sidewall height | 3.86 in | 3.51 in | −0.34 in |
| Circumference | 83.9 in | 81.8 in | −2.2 in |
| Revs per mile (nominal) | 755 | 775 | +20 |
| Wheel diameter | 19 in | 19 in | ±0 in |
| Diameter in mm | 679 | 661 | −18 mm |
Speedometer difference
Your speedometer is calibrated for 245/40R19. Fitted with 255/35R19, the actual speed is the reading × 26.03 ÷ 26.72.
| Speedometer shows | Actual speed | Difference |
|---|---|---|
| 20 mph | 19.5 mph | −0.5 mph |
| 30 mph | 29.2 mph | −0.8 mph |
| 45 mph | 43.8 mph | −1.2 mph |
| 55 mph | 53.6 mph | −1.4 mph |
| 60 mph | 58.5 mph | −1.5 mph |
| 70 mph | 68.2 mph | −1.8 mph |
| 80 mph | 77.9 mph | −2.1 mph |
Real tires: published diameters
245/40R19: 26.5–27 in published by 7 makers; 255/35R19: 25.8–26.1 in published by 5 makers. Calculated figures assume a nominal tire; the exact difference between two specific tires depends on their models.
More about each size: 245/40R19 · 255/35R19
Related comparisons
FAQ
Which is bigger, 245/40R19 or 255/35R19?
255/35R19 is −2.6% shorter than 245/40R19: 26.0 in vs 26.7 in (−0.69 in).
How much will my speedometer be off with 255/35R19 instead of 245/40R19?
The speedometer is calibrated for 245/40R19. With 255/35R19 it shows 60 mph when you are doing 58.5 mph, and 70 mph at 68.2 mph (−2.6%). Your speedometer also has its own factory tolerance.
Can I replace 245/40R19 with 255/35R19?
The diameter difference is −2.6%. 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.