Question 1

Which tire is taller, 215/40 R18 or 255/35 R19?

Accepted Answer

255/35 R19 is taller by 31.9 mm (5.07%) compared with 215/40 R18.

Question 2

What is the diameter difference between 215/40 R18 and 255/35 R19?

Accepted Answer

215/40 R18 measures 629 mm overall diameter, 255/35 R19 measures 661 mm — a difference of 31.9 mm (5.07%).

Question 3

How much speedometer error does this change create?

Accepted Answer

Switching from 215/40 R18 to 255/35 R19 changes the speedometer reading by +5.07%. At an indicated 100 km/h, your true speed becomes about 105.1 km/h.

Question 4

Is 255/35 R19 a safe replacement for 215/40 R18?

Accepted Answer

Over 5% diameter difference. This is outside the common safe range and can affect speedometer accuracy, ABS calibration and gearing. Not recommended without professional review.

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	215/40 R18	255/35 R19	Difference
Overall diameter	629.2 mm	661.1 mm	+31.9 mm (+5.07%)
Sidewall height	86.0 mm	89.3 mm	+3.3 mm
Circumference	1.977 m	2.077 m	+100.2 mm
Revs / km	505.9	481.5	-24.4
Ground clearance	reference	+15.9 mm	+15.9 mm
Speedometer @ 100 km/h	100.0 km/h	105.1 km/h	+5.07 km/h

215/40 R18 vs 255/35 R19

Detailed comparison

Verdict: danger

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