Workshop Tools
Tire Calculator
Select two wheel and tire setups below. The calculator shows the difference in overall diameter, sidewall height, wheel position, and speedometer reading.
01 · Setups
02 · Results
Actual speed when the speedometer shows 100 km/h
100.3km/h
The speedometer reading is 0.3 km/h too low per 100 km/h with setup B installed.
Diameter Δ
+2 mm
+0.3%
Ride height Δ
+1 mm
taller
Poke Δ
+21 mm
further out
Inboard Δ
+17 mm
toward suspension
- Overall diameter changes by +0.3%. A difference within ±1.5% is generally safe.
- The wheel face moves about 21 mm outward. Check fender clearance.
- The inner rim edge moves about 17 mm closer to the suspension. Check strut and control arm clearance.
- The tread is 20 mm wider, which increases grip and rolling resistance.
| Specification | A · Current | B · New |
|---|---|---|
| Tire size | 215/55 R17 | 235/40 R19 |
| Wheel | 17 × 7.0J ET40 | 19 × 8.5J ET38 |
| Section width | 215 mm | 235 mm |
| Sidewall | 118 mm | 94 mm |
| Overall Ø | 668 mm (26.3″) | 671 mm (26.4″) |
| Circumference | 2100 mm | 2107 mm |
| Revs per km | 476 | 475 |
| Backspacing | 142 mm | 159 mm |
Results are calculated from the entered dimensions only. Actual fitment depends on the vehicle. Contact us to check a setup before buying.
Next step
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