Question 1

Which tire is taller, 275/40 R22 or 255/50 R20?

Accepted Answer

275/40 R22 is taller by 15.8 mm (2.03%) compared with 255/50 R20.

Question 2

What is the diameter difference between 275/40 R22 and 255/50 R20?

Accepted Answer

275/40 R22 measures 779 mm overall diameter, 255/50 R20 measures 763 mm — a difference of 15.8 mm (2.03%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 275/40 R22 to 255/50 R20 changes the speedometer reading by -2.03%. At an indicated 100 km/h, your true speed becomes about 98.0 km/h.

Question 4

Is 255/50 R20 a safe replacement for 275/40 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	275/40 R22	255/50 R20	Difference
Overall diameter	778.8 mm	763.0 mm	-15.8 mm (-2.03%)
Sidewall height	110.0 mm	127.5 mm	+17.5 mm
Circumference	2.447 m	2.397 m	-49.6 mm
Revs / km	408.7	417.2	+8.5
Ground clearance	reference	-7.9 mm	-7.9 mm
Speedometer @ 100 km/h	100.0 km/h	98.0 km/h	-2.03 km/h

275/40 R22 vs 255/50 R20

Detailed comparison

Verdict: excellent

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