Free wheel and tyre tools
Tyre stretch calculator
Estimate a starting rim width range and see whether a tyre may look meaty, neutral or taut. ETRTO-style guidance, subject to tyre maker approval.
How it works
Tyre width alone cannot tell you which rims are approved. This tool uses an ETRTO-style measuring-rim estimate that also considers aspect ratio, rounded to the nearest half inch. We show a conservative starting band half an inch either side. This is our screening guidance, not an official ETRTO approved-rim table. The exact tyre manufacturer's approved range takes precedence.
Read the ETRTO recommendations and check approved widths in your tyre maker's product specifications.
A worked example
For a 225 mm tyre with a 45% profile, the estimated measuring rim is 7.5 inches. Our starting band is 7 to 8 inches. A 7 inch rim suggests a fuller sidewall; an 8 inch rim suggests a more taut one. A particular 225/45 R17 tyre may have a different approved range, so look up that exact product before fitting it.
Quick reference
Estimated starting rim widths for common tyres
| Tyre | Measuring rim estimate | Starting band |
|---|---|---|
| 195/50 | 6 inch | 5.5 to 6.5 inch |
| 205/45 | 7 inch | 6.5 to 7.5 inch |
| 215/45 | 7 inch | 6.5 to 7.5 inch |
| 225/45 | 7.5 inch | 7 to 8 inch |
| 225/40 | 7.5 inch | 7 to 8 inch |
| 235/40 | 8 inch | 7.5 to 8.5 inch |
| 245/40 | 8 inch | 7.5 to 8.5 inch |
| 255/35 | 8.5 inch | 8 to 9 inch |
| 265/35 | 9 inch | 8.5 to 9.5 inch |
| 275/35 | 9 inch | 8.5 to 9.5 inch |
Our screening estimate, not an approved range. The exact tyre maker's published rim widths take priority.
Explained in our guides
- Tyre stretch explained: appearance, approval and safetyUnderstand what stretched tyres are, distinguish a taut approved fit from an unapproved rim width, and assess the safety claims without forum folklore.
- How to choose wheel width for a tyre: use the approved rangeChoose a rim width using the exact tyre manufacturer's data, distinguish measuring rims from approved ranges, and check the effect on inner and outer clearance.
Questions
Is this an official ETRTO approval?
No. It is preliminary guidance based on a measuring-rim estimate. We do not reproduce or certify against the ETRTO approved-size tables. Check the tyre manufacturer's approved rim widths for the full size and exact model.
What do meaty and taut mean here?
They describe the likely sidewall shape relative to the estimated measuring rim. A narrower rim tends to create a fuller sidewall; a wider rim tends to pull it more taut. They do not measure grip or certify that the tyre is safe to mount.
Can I fit a tyre outside its manufacturer's approved range?
Do not use this calculator to justify doing so. A combination outside the approved range can affect bead seating, load capacity and handling. Ask a qualified tyre professional to specify an approved combination.
Keep checking
Use these results to plan a setup. Confirm fitment, tyre approval and clearances with a qualified professional before buying or fitting parts.