CalculatorsRim and Tire ETRTO Checker
Rim and Tire ETRTO Checker
Inner rim width and tyre width have to agree. Too narrow a tyre on a wide rim comes off in a corner; too wide a tyre on a narrow rim squirms.
Inputs
Results
- Widths agree
- Yes
How the number is made
Listed inner widths and tyre bands: 13 mm fits 18–25, 15 mm 23–32, 17 mm 25–37, 19 mm 28–47, 21 mm 28–52, 23 mm 35–58, 25 mm 40–64, 30 mm 47–76. Any other inner width uses the nearest listed row. A tie, such as 20 mm halfway between 19 and 21, uses the narrower row.
Hookless rims add their own minimum tyre width and maximum pressure. This is the width pairing only.
Related calculators
- Tire Pressure Calculator
Once the width is legal, set the pressure for your weight.
- Tubeless Sealant Calculator
A compatible tubeless tyre still needs a measured fill.
Questions
Where is inner width measured?
Across the rim bed between the bead hooks, not the outside of the rim.
My tyre mounted anyway. Is it fine?
Mounting is not the same as a supported width. A blow-off usually happens later, in a turn or on a hot day.
Is a 28 mm tyre allowed on a 21 mm rim?
Yes. The 21 mm rim band starts at 28 mm. A 23 mm tyre on that rim is not allowed. A width exactly halfway between two rim rows uses the narrower row.
Related gear
- Digital caliper
Inner width is printed on some rims and missing on others. Measure the bead-seat gap.
$15–$40