Question 1

Which tire is taller, 275/35 R21 or 315/30 R22?

Accepted Answer

315/30 R22 is taller by 21.9 mm (3.02%) compared with 275/35 R21.

Question 2

What is the diameter difference between 275/35 R21 and 315/30 R22?

Accepted Answer

275/35 R21 measures 726 mm overall diameter, 315/30 R22 measures 748 mm — a difference of 21.9 mm (3.02%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 275/35 R21 to 315/30 R22 changes the speedometer reading by +3.02%. At an indicated 100 km/h, your true speed becomes about 103.0 km/h.

Question 4

Is 315/30 R22 a safe replacement for 275/35 R21?

Accepted Answer

Between 3% and 5% diameter difference — speedometer drift is noticeable. Consider recalibration and confirm clearance with your vehicle's manufacturer specification.

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	275/35 R21	315/30 R22	Difference
Overall diameter	725.9 mm	747.8 mm	+21.9 mm (+3.02%)
Sidewall height	96.3 mm	94.5 mm	-1.8 mm
Circumference	2.280 m	2.349 m	+68.8 mm
Revs / km	438.5	425.7	-12.8
Ground clearance	reference	+10.9 mm	+10.9 mm
Speedometer @ 100 km/h	100.0 km/h	103.0 km/h	+3.02 km/h

275/35 R21 vs 315/30 R22

Detailed comparison

Verdict: warning

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