Comparison
255/35 R21 vs 285/35 R21
Stepping from 255/35 R21 to 285/35 R21 keeps the 21-inch wheel but widens the section by 30 mm. This tire combination moves rolling diameter a touch off the original spec. More tread on the ground tends to improve dry grip and stance, with a small fuel-economy and clearance tradeoff.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. Overall the swap sits inside the safe ±3% diameter window, so ABS, traction control and gearing behave normally.
TakeUseful when extra dry grip and stance matter more than a small fuel-economy hit.
Quick math: 285/35 R21 is 21.0 mm taller than 255/35 R21, shifting the speedometer by +2.95%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+21.0 mm
2.95%
Speedometer at 100
102.9 km/h
+2.95% error
Ground clearance
+10.5 mm
ride height delta
Sidewall change
+10.5 mm
revs/km: 434.3
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/compare/255-35-r21-vs-285-35-r21Detailed comparison
| Metric | 255/35 R21 | 285/35 R21 | Difference |
|---|---|---|---|
| Overall diameter | 711.9 mm | 732.9 mm | +21.0 mm (+2.95%) |
| Sidewall height | 89.3 mm | 99.8 mm | +10.5 mm |
| Circumference | 2.236 m | 2.302 m | +66.0 mm |
| Revs / km | 447.1 | 434.3 | -12.8 |
| Ground clearance | reference | +10.5 mm | +10.5 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 102.9 km/h | +2.95 km/h |
Verdict: excellent
Within ±3% — speedometer, ABS and traction control should behave normally.
Speedometer impact
At a true 100 km/h, your dashboard will read 102.9 km/h after switching to 285/35 R21 — a +2.95% offset. Use the speedometer error calculator to recheck for other indicated speeds, and the speedometer error guide for the full background.
Ground clearance change
The new tire's half-diameter changes ride height by +10.5 mm. Small differences are absorbed by suspension travel, but anything beyond ±10 mm can affect headlight aim, fender clearance and bump-stop margin. See the plus-sizing guide before committing.
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255/35 R21
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285/35 R21
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