Comparison
245/35 R20 vs 265/40 R18
Minus-sizing from 245/35 R20 to 265/40 R18 pairs a smaller 18-inch wheel with more rubber between the rim and road. This wheel and tire pairing moves rolling diameter a touch off the original spec.
The speedometer offset is small but measurable; worth keeping in mind if you watch the dash closely. The taller sidewall adds cushioning over potholes and rougher roads, with a softer overall ride. Extra width broadens the footprint for more grip, but check inner liner and strut clearance before fitting. The smaller wheel is also lighter and easier to find affordable winter rubber for. Diameter change stays inside the conservative ±3% safety window — an OEM-safe fitment on most vehicles.
TakeTypical choice for a dedicated winter or off-road setup where extra sidewall pays off.
Quick math: 265/40 R18 is 10.3 mm shorter than 245/35 R20, shifting the speedometer by -1.52%.
Current Tire
New Tire
Ground line · scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
-10.3 mm
-1.52%
Speedometer at 100
98.5 km/h
-1.52% error
Ground clearance
-5.1 mm
ride height delta
Sidewall change
+20.3 mm
revs/km: 475.7
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/compare/245-35-r20-vs-265-40-r18Detailed comparison
| Metric | 245/35 R20 | 265/40 R18 | Difference |
|---|---|---|---|
| Overall diameter | 679.5 mm | 669.2 mm | -10.3 mm (-1.52%) |
| Sidewall height | 85.8 mm | 106.0 mm | +20.3 mm |
| Circumference | 2.135 m | 2.102 m | -32.4 mm |
| Revs / km | 468.4 | 475.7 | +7.2 |
| Ground clearance | reference | -5.1 mm | -5.1 mm |
| Speedometer @ 100 km/h | 100.0 km/h | 98.5 km/h | -1.52 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 98.5 km/h after switching to 265/40 R18 — a -1.52% 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 -5.1 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.
Back to
245/35 R20
Back to
265/40 R18
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