Tire Size Comparison
Will the new size work? Compare diameter, width and circumference, see how far off the speedometer lands, and get a drivetrain-aware verdict — not just a bare percentage.
Diameter difference+2.2%
Actual speed when speedo reads 60 mph59 mph
Within limits2.24% diameter differenceUnder the conservative 3% community threshold.
| Measure | Current | New | Diff |
|---|---|---|---|
| Overall diameter | 26.16 in | 26.74 in | +2.24% |
| Section width | 8.46 in | 8.86 in | +4.7% |
| Sidewall height | 5.08 in | 4.87 in | -4.1% |
| Circumference | 82.18 in | 84.02 in | +2.24% |
| Revs per mile | 771 | 754 | -2.19% |
How the verdict works: under 3% diameter difference is the conservative community consensus for "safe" — the threshold many tire shops use. Between 3% and 5% is a genuine grey zone (some guides allow it, others don't). Over 5% risks rubbing and gearing issues on any drivetrain. Read the 3% vs 5% debate in detail.
AWD is different: full-time AWD cares about circumference, not just percentage. Community-documented damage starts around 0.5 in circumference difference (vibration under acceleration) and 0.75 in (differential and transfer-case destruction; one owner measured 6.7% difference before the transfer case failed). See the AWD mismatched tires guide.
Spare tire rule of thumb: a temporary spare should match the driven axle's circumference within about 0.25 in, and never be a smaller diameter on a driven axle for an AWD vehicle. Check the load index too — a donut spare is rated for roughly 50 miles.
Assumptions & sources
Green threshold< 3% diameter diffCommunity consensus (rules-inventory A1) — conservative shops
Grey zone3–5%Documented disagreement: 3%-school vs 5%-school (rules-inventory A1/A2)
AWD yellow> 0.5 in circumference diffCommunity verbatim: shudder under acceleration
AWD red> 0.75 in circumference diffCommunity verbatim: diff/transfer-case damage; 6.7% case documented
LSD / G80 caution> 1% circumference diffCommunity: lockup intervention on mismatched axles
Frequently asked questions
Is a 2% tire size difference okay?
Almost always, yes. A 2% difference in overall diameter shifts the speedometer by about 1 mph at highway speeds and is well inside the conservative 3% threshold — for open differentials this is a green result.
Can I run different tire sizes on an AWD car?
Not for long. Full-time AWD systems heat up and self-destruct when the axles rotate at different speeds. Community-documented failures start around 0.5 in of circumference difference; a 6.7% mismatch destroyed one owner's transfer case. If you must mix, put the pair with equal circumference on the same axle and keep the difference under 0.25 in.
Why does my speedometer read wrong after bigger tires?
The speedometer is calibrated to the stock revs per mile. A taller tire covers more ground per revolution, so at a true 60 mph the wheels turn slower and the speedometer reads low. The comparison table shows the actual speed when the display reads 60 mph.
What about the odometer?
It errs by the same factor as the speedometer: with tires 2% taller, the odometer under-records by about 2%. Over 100,000 miles that is roughly 2,000 "free" miles not counted — relevant for lease and resale math.