Question 1

Which tire is taller, 285/35 R22 or 265/40 R21?

Accepted Answer

285/35 R22 is taller by 12.9 mm (1.70%) compared with 265/40 R21.

Question 2

What is the diameter difference between 285/35 R22 and 265/40 R21?

Accepted Answer

285/35 R22 measures 758 mm overall diameter, 265/40 R21 measures 745 mm — a difference of 12.9 mm (1.70%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 285/35 R22 to 265/40 R21 changes the speedometer reading by -1.70%. At an indicated 100 km/h, your true speed becomes about 98.3 km/h.

Question 4

Is 265/40 R21 a safe replacement for 285/35 R22?

Accepted Answer

Within ±3% diameter — generally considered a safe replacement from a speedometer-error standpoint, provided wheel offset, rim width and clearance also match your vehicle.

Question 5

What else should I check before changing tire size?

Accepted Answer

Beyond diameter and speedometer error, verify wheel offset (ET), rim width, hub bore, load index, brake and suspension clearance, and your vehicle's manufacturer specification. Local regulations may also limit how far you can deviate from OEM.

Metric	285/35 R22	265/40 R21	Difference
Overall diameter	758.3 mm	745.4 mm	-12.9 mm (-1.70%)
Sidewall height	99.8 mm	106.0 mm	+6.3 mm
Circumference	2.382 m	2.342 m	-40.5 mm
Revs / km	419.8	427.0	+7.3
Ground clearance	reference	-6.4 mm	-6.4 mm
Speedometer @ 100 km/h	100.0 km/h	98.3 km/h	-1.70 km/h

285/35 R22 vs 265/40 R21

Detailed comparison

Verdict: excellent

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