Confusion about what tyre width will fit on my wheels ....

I have Jalco DM25 rims on my Ridgeback Expedition bike, 26" wheels. I'm struggling to make sense of understanding the range of widths that will go on this wheel. I've looked at various sites like

but to be honest, it doesn't appear to be in English :-)

So, can anyone point me to a guide for idiots, that explains what I need to look for when sizing a tyre for a rim, please? Will 26 x 1.5" fir on this, or is it too small?

Any help appreciated.



  • akh
    akh Posts: 206
    Do some research based on the below, but a cursory Google suggests it will likely be fine. Fine does not necessarily mean optimal, or even good.

    You want to compare the internal width of the rim with the actual width of the tyre. Most guides online will reference those two dimensions. They will probably reference a European system, which won't be in inches like you've given. It's worth figuring out the equivalent for your particular rim. A 700c road wheel is also 622 for example, I don't know the equivalent for 26" off the top of my head.

    A tyre which is far too narrow will not seat properly and be unsafe. A tyre which is far too large won't be properly supported by the rim and can be unstable in corners, or form a 'lightbulb' shape on the rim. The safe range is pretty wide, a lot wider than the optimal range. Most guides advise it is safe to run a tyre far larger than anyone does in practice on a given rim.

    A quick Google suggests your rims have an internal width of 18mm, and 1.5" in pretty much 38mm (assuming the sizing is accurate, it may not be). That's safe, but double check for yourself. I'm running 38mm tyres on 19mm rims without issues. A slightly wider rim would probably be optimal, but it's been fine for me. The profile and construction of the individual tyre makes a big difference though. My tyres have a minimal 'file' tread pattern and form a nice shape on the rim, a tyre with tread blocks may be more sensitive.

  • Thanks for this. It's really helpful and helps. I'll continue to read about this, but am intending to get some 1.5" wide slicks for the bike soon for fun, so slowly slowly catchy monkey!