Why does rim width matter?

Rim width affects tyre shape, contact patch, rolling resistance and handling. A rim that is too narrow causes a bulging tyre profile; too wide and the tyre becomes stretched and prone to burping.

What is the 105% rule?

A common guideline is that the tyre should be 1.4-2.0x the internal rim width. For example, a 19mm internal rim works well with 25-38mm tyres. However, modern wide rims are changing these guidelines.

Are wider rims better?

Wider rims provide better tyre support, a rounder tyre profile, and improved cornering grip. They also allow lower tyre pressures without sidewall collapse. The trend is towards wider rims across all disciplines.

Can I put narrow tyres on wide rims?

There are safety limits. A tyre narrower than the internal rim width should not be used. Check ETRTO compatibility charts. As a rule, tyre width should be at least 1.3x the internal rim width.

What about hookless rims?

Hookless rims require specific tyre compatibility (check manufacturer lists). They typically require slightly wider tyres relative to rim width and have specific pressure limits.

BikeCalcs

Rim Width Calculator — Optimal Rim for Your Tyres

Find the optimal internal rim width for your tyre size and riding style.

Tyre Width

Riding Type

How We Calculate This

Rim Width Calculation

Optimal internal width = Tyre width x Optimal ratio (60-72%)
Race: 60% ratio (narrower rim for aero)
Road: 65% ratio (balanced)
Gravel: 68% ratio (stability at low pressure)
MTB: 72% ratio (maximum tyre support)
External width = Internal + ~5mm (rim wall thickness)

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.