Enter stock and new sizes. See overall diameter, sidewall, Δ%, and speedometer error from public tire geometry.
A size such as 225/65R17 is the section width in millimetres, the aspect ratio, and the rim diameter in inches. Overall diameter (mm) = rim × 25.4 + 2 × sidewall. Sidewall height (mm) = section × aspect / 100.
Actual speed = indicated speed × new overall diameter / stock overall diameter. Percent error = (new diameter − stock diameter) / stock diameter.
Stock 225/65R17 has sidewall ১৪৬.২৫ mm and overall diameter ৭২৪.৩ mm. New 235/60R18 has sidewall ১৪১ mm and overall diameter ৭৩৯.২ mm. Diameter change +১৪.৯ mm (+২.০৬ %). At an indicated ৬০ km/h, actual speed is ৬১.২ km/h. Speedometer error +২.০৬ %.
225/65R17 decodes as section ২২৫ mm, aspect ৬৫, rim ১৭ in.
235/60R18 decodes as section ২৩৫ mm, aspect ৬০, rim ১৮ in.
Outlines are drawn at true scale and share a ground line.
Diameter change
+১৪.৯ mm
Δ%
+২.০৬ %
আসল গতি
৬১.২ km/h
স্পিডো ত্রুটি
+২.০৬ %
| 225/65R17 | 235/60R18 | Δ | |
|---|---|---|---|
| Section width | ২২৫ mm | ২৩৫ mm | +১০ mm |
| Sidewall height | ১৪৬.২৫ mm | ১৪১ mm | -৫.২৫ mm |
| মোট ব্যাস | ৭২৪.৩ mm | ৭৩৯.২ mm | +১৪.৯ mm |
| পরিধি | ২,২৭৫.৫ mm | ২,৩২২.৩ mm | +৪৬.৮ mm |
| পাক | ৪৩৯.৫ /km | ৪৩০.৬ /km | -৮.৯ /km |
Estimates from public tire geometry. Not a fitment certificate and not a legal speedometer certification.
Enter a rim width and an offset (ET) for each wheel. The sketch aligns the hub faces and shows the change in outer lip position. This is relative Δ poke, not fender clearance for a specific car.
Outer position from the hub face (mm) = (rim width in inches × 25.4) / 2 − offset (mm). Relative Δ poke = new − stock. Positive means the new lip sits farther out.
Example wheels, not a car: a 7.5 in rim at ET 45 sits ৫০.২৫ mm from the hub face. A 8.5 in rim at ET 35 sits ৭২.৯৫ mm. Relative Δ poke is +২২.৭ mm.