how I can find the tyre clearance

[Frankfairhurst]

Does anyone know how I can work out what clearance is needed from the tyre info .ie 25 x 622..25 mm it tells me the tyre width but do I assume it's the height as well ?

[Jdsk]

Welcome.

Is this about how sizing systems work?
https://sheldonbrown.com/tire-sizing.html

Or about whether a particular tyre (and wheel) will fit a particular bike?

Jonathan

[Paulatic]

Yes with road bike tyres a 25 will usually be 25 both ways as will 28mm be.
Not sure if this applies to fatter tyres though. I’ll have to measure MtB next time I’m in the shed.

[mjr]

Yes with road bike tyres a 25 will usually be 25 both ways as will 28mm be.
Not sure if this applies to fatter tyres though. I’ll have to measure MtB next time I’m in the shed.

It generally applies to all tyres. Tyre construction can change it a bit but it's limited because ultimately the round inner tube pushes out in all directions equally. I've definitely seen 4mm height-width difference on some rims and I suspect a little over 10% may be possible. I think such tyres are written ww / hh - ddd in the modern format.

[Frankfairhurst]

Welcome.

Is this about how sizing systems work?
https://sheldonbrown.com/tire-sizing.html

Or about whether a particular tyre (and wheel) will fit a particular bike?

Jonathan

Thanks for the comprehensive data .I see no trade standard so will work on width +10%

[axel_knutt]

It's worth bearing in mind that tyre tolerances are surprisingly large (+/-3mm).

[andrew_s]

The inside of an inflated tyre is circular in cross section, with the bottom of the circle being based about level with the bead seat, giving 311+ 25 mm = 336 mm for a 700 x 25 tyre.
However, whilst the sidewalls are thin, the tread on top of the tyre usually isn't, so there's some extra to add to the width to get the height for working out clearances.
For a slick tyre, the extra may only be 1 or 2 mm, but for a Marathon Plus (with its 5-6 mm of blue anti-puncture rubber, plus a decent amount of tread) or an MTB knobbly the extra may reach 10 mm or more.

[scottg]

Does anyone know how I can work out what clearance is needed from the tyre info .ie 25 x 622..25 mm it tells me the tyre width but do I assume it's the height as well ?

The internal rim width will also affect inflated tyre dimensions, also tyres are a bit smaller when first installed,
depending on tyre construction, for example a tyre marked as 36mm will measure 35mm when first installed,
and expand to 36mm after a few hundred miles.

You could make a tyre fit gauge.
https://www.renehersecycles.com/shop/eq ... fit-gauge/

[Paul_R]

The inside of an inflated tyre is circular in cross section, with the bottom of the circle being based about level with the bead seat, giving 311+ 25 mm = 336 mm for a 700 x 25 tyre.

Hi Andrew, I'm on a fact finding journey to get new tyres for my bike and came across this post.
I cant understand/work out where '311' comes from for a 25mm tyre.......would you mind showing how you arrive at 311 please.
Many thanks
Paul

[Jdsk]

It comes from the diameter of the bead seat of the rim of a "700" wheel:

Screenshot 2026-07-15 at 22.32.45.png (7 KiB) Viewed 460 times

https://sheldonbrown.com/tire-sizing.html

and 622/2 = 311 mm

Jonathan

[plancashire]

Schwalbe do not specify tyre height on their website. As there is no rule or specification, only approximations, I suggest you try to find a tyre you are interested in fitted to a wheel the same size as yours and measure it (don't forget the distance from rim edge to bead seat, which may be slightly different in your wheels). A very cooperative bike shop might do this or say they know the answer. If you make the total diameter clear when you buy it is a condition of sale and you can return the tyre if it doesn't fit.

[rogerzilla]

The quoted tyre width is at best an approximation; sometimes a marketing lie to get a lower weight. I've had 25mm tyres that were really 22mm and 35mm tyres that fouled a mudguard where another brand's 35mm tyre fitted easily.