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How do I measure the maximum tire clearance on my frame?

By Crankworthy · Published · Updated

Short answer

Measure the narrowest gap around your current inflated tyre — usually between the chainstays behind the bottom bracket, at the seatstays and under the fork crown — and leave a few millimetres each side for mud and flex. On rim-brake bikes the brake calipers are often the real limit.

Where on your bikeTyres, frame and fork

Measuring tyre clearance between the chainstaysSeen from behind: the inflated tyre sits between the two chainstays with a gap each side. The widest tyre is roughly the current tyre’s width plus both gaps, minus a safety margin each side.Measure the tightest spot (from behind)current tyrestaystaygapgapwidest tyre ≈ current tyre+ both gaps− a safety margin each side
Do the same at the seatstays and under the fork crown, and work from the smallest gap. If the frame maker publishes a maximum tyre size, that number wins.

Where the limits are

The limit is almost never the tyre; it is the space around it. The tightest spots are usually between the chainstays near the bottom bracket, between the seatstays, and under the fork crown.

Leave clearance for mud, wheel flex in corners and tyres that grow slightly once inflated. A tyre that only just clears when clean will rub on the trail.

On rim-brake bikes, the tyre must also pass between the brake arms and under the caliper. Older road rim-brake frames are often limited here before the frame itself — a 28mm tyre may fit where a 30mm will not.

Rim internal width affects how wide a tyre actually sits. The same labelled tyre measures wider on a wider rim, so measure it on your own wheels.

How to measure

Measure the narrowest gap
With your current tyre fitted and inflated, measure the gap on each side at the chainstays, seatstays and fork crown. The smallest number is your margin.
Add it up
Current tyre width, plus the smallest gap on both sides, minus a few millimetres of safety margin each side, is roughly the widest tyre that will work.
Check the frame spec
Many manufacturers publish a maximum tyre size. It is the safest number to work from.

Skip

Don’t buy: a tyre that only just clears when clean
Instead: one size down, leaving room for mud, flex and the tyre growing once inflated.

Makers’ stated maximums

From our research, the maximum tyre size each maker lists for these bikes — the number to work from when it exists.

Tires in our catalog

Check the width and wheel size of each against your measured clearance.

Prices were last checked when the catalog was built and can change at any time. Retailer links are affiliate links; we may earn a commission at no extra cost to you.

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