Examples
Examples
Try the starting example
- Original tire: section width mm, aspect %, rim inches
- 205,55,16
- Replacement nominal tire dimensions in same order
- 225,45,17
- Indicated speed in any consistent speed unit
- 60
- Indicated distance in any consistent distance unit
- 100
- Original and replacement nominal diameters (mm)
- 631.9, 634.3
- Modeled actual speed at indicated speed
- 60.227884
- Nominal diameter/speed percentage change
- 0.379807
- Modeled actual distance at indicated distance
- 100.379807
Try another scenario
- Original tire: section width mm, aspect %, rim inches
- 205,55,16
- Replacement nominal tire dimensions in same order
- 235,40,18
- Indicated speed in any consistent speed unit
- 60
- Indicated distance in any consistent distance unit
- 100
- Original and replacement nominal diameters (mm)
- 631.9, 645.2
- Modeled actual speed at indicated speed
- 61.262858
- Nominal diameter/speed percentage change
- 2.104763
- Modeled actual distance at indicated distance
- 102.104763
Calculation method
Calculation method
Original and replacement nominal diameters (mm)
Compute both nominal marking diameters using 25.4 mm/inch.
Modeled actual speed at indicated speed
Indicated speed×new nominal diameter/original nominal diameter.
Nominal diameter/speed percentage change
100×(new/original−1).
Modeled actual distance at indicated distance
Indicated distance×new/original, assuming calibration remains for original nominal circumference.
Symbols and units
- a
- Original tire: section width mm, aspect %, rim inches
- b
- Replacement nominal tire dimensions in same order
- c
- Indicated speed in any consistent speed unit
- d
- Indicated distance in any consistent distance unit
Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.
Assumptions & limits
Assumptions & limits
- A nominal diameter-ratio scenario, not a measured speedometer calibration or tire-fit approval. It assumes unchanged gearing/electronics and proportional rolling circumference; actual loaded rollout may differ.
Are these inputs private?
These calculations run in your browser. A shared link contains the values you choose to share. Only questions submitted to the separate AI finder are sent to OpenAI.
Further reading
Michelin: nominal tire width, aspect ratio and rim-diameter markings ↗
Background reading; this does not imply endorsement or independent review of SumFizz.