Examples
Examples
Try the starting example
- Original front tire: width mm, aspect %, rim inches
- 120,70,17
- New front tire in same order
- 120,80,17
- Original rear tire in same order
- 180,55,17
- New rear tire in same order
- 190,55,17
- Fixed horizontal axle spacing for idealized pitch (mm)
- 1400
- Nominal front and rear axle-height changes (mm)
- 12, 5.5
- Idealized front-up body pitch change (degrees)
- 0.266014
- Mean of nominal axle-height changes (mm)
- 8.75
Try another scenario
- Original front tire: width mm, aspect %, rim inches
- 120,70,17
- New front tire in same order
- 130,70,17
- Original rear tire in same order
- 180,55,17
- New rear tire in same order
- 190,55,17
- Fixed horizontal axle spacing for idealized pitch (mm)
- 1400
- Nominal front and rear axle-height changes (mm)
- 7, 5.5
- Idealized front-up body pitch change (degrees)
- 0.061388
- Mean of nominal axle-height changes (mm)
- 6.25
Calculation method
Calculation method
Nominal front and rear axle-height changes (mm)
Half new-minus-original nominal tire diameter independently at each axle.
Idealized front-up body pitch change (degrees)
atan((front height change−rear height change)/fixed horizontal axle spacing).
Mean of nominal axle-height changes (mm)
Average the two nominal height changes; no actual chassis clearance is inferred.
Symbols and units
- a
- Original front tire: width mm, aspect %, rim inches
- b
- New front tire in same order
- c
- Original rear tire in same order
- d
- New rear tire in same order
- e
- Fixed horizontal axle spacing for idealized pitch (mm)
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
- Nominal marking-radius and rigid fixed-horizontal-spacing geometry. Actual tire profiles, load deflection, suspension, rake/trail, steering and fitment suitability are not modeled or approved.
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.