MTB tyre on 80’s Peugeot Road bike 597mm rims


New Member
I’m trying to replace the tyres on my old 1980’s Peugeot bike. The rims are 597mm and it currently has 26” 1.25 “ tyres. There doesn’t seem to be many options, but there are a fair few MTB tyres that are exactly the same size (26” 1.25”) as my current ones. I wondered if these will fit? Also, is there any difference on how you put on a MTB tyre vs a road bike one if they both have a wired beading?

here’s the bike: (I have since taken the mud guard off)


This is the tyre I was looking at:




Legendary Member
No. That won't work. Welcome to the crazy world of bike tyre sizing. You need 597 ERTO tyres which are usually sold as as 26 x 1 1/4.

MTB tyres are 559mm ERTO and are an American size. Anything that is 26 x 1.x will not fit. Neither will the more common 26 x 1 3/8"

26 x 1 3/8" is 590mm, a traditional British size usually found on utility bikes.

26 x 1 1/4 is a traditional British size usually found on smaller framed sports bikes like yours. It is 597mm.

26 x some decimal size is the American size usually found on old American cruisers or more recently on MTBs and is 559mm in the newer sizing.

None of these are interchangeable. 26" refers to the overall diameter of the wheel and tire and not diameter of the rim. 26 x1 3/8" is fatter than the 26 x 1 1/4" so the rim is 7mm bigger in diameter to allow for the thinner tyre and still have a 26 inch diameter wheel.

The American size 26 inch is rarely close to 26" in diameter nowadays unless you are using a balloon tyre as was originally specified for this wheel size.
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