WebToolArcPractical guide and verification
Compare geometry before thinking about fitment
The size code gives a theoretical section width, sidewall and unloaded diameter. Compare those dimensions first, then treat clearance as a separate vehicle-specific question. Actual mounted dimensions can vary by tire model, approved rim width, pressure, load and wear.
Use the speed table as a ratio check
If the replacement tire has a larger rolling diameter, the vehicle travels farther per wheel revolution and theoretical road speed rises relative to the indicated speed. The reverse happens with a smaller diameter. Verify the direction of the error before relying on a single percentage.
Ride-height change is only half the diameter change
A diameter increase is split above and below the axle, so nominal ride-height change is approximately one half of the diameter difference. That geometric change does not prove suspension, fender, brake or steering clearance.
Keep wheel and tire constraints separate
Tire size alone does not establish compatible rim width, wheel offset, load index, speed rating or inflation requirement. Confirm manufacturer fitment data and vehicle limits before treating a mathematically similar size as a safe substitute.
Measure real rolling behavior when calibration matters
Tread wear, pressure, load and construction change effective rolling radius. For speedometer or odometer work that matters in practice, compare the theoretical result with a reliable measured reference after installation rather than assuming catalog dimensions are exact.