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Same wheel size tyres not fitting

  • 22-11-2021 7:57pm
    Registered Users Posts: 162 ✭✭

    I bought a Raleigh road bike for my 6 year old. It has 24 X 1 or 25-520 Kenda tyres on it. He's doing some cyclo-cross so I found some Kenda 24x1 3/8 or 37-520 tyres in the UK and bought them.

    Have received the tyres today and went to fit them but the inner diameter of the bead on the CX tyres seems to be at least 1 inch too long and the tyres won't fit. Am I stupid and missing something here as I assumed they would fit the existing rims no issues.


  • Moderators, Category Moderators, Arts Moderators, Sports Moderators Posts: 47,826 CMod ✭✭✭✭magicbastarder

    did you confirm the size stamped on the tyre wall matched what you ordered?

  • Registered Users Posts: 162 ✭✭pairofpears

    The only thing different is the width of the tyre as their CX tyres compared to the 1" road tyres on it currently. Everything stacks up the same until it comes to putting the tyres on wheel and its too big.

  • Registered Users Posts: 491 ✭✭Elvis Hammond

    Are you sure they're not stamped 540?

  • Registered Users Posts: 162 ✭✭pairofpears

    I will have to check that tonight but Im fairly sure what I wrote in the initial post is correct as I had been staring at the wheels for a good half hour scratching my head and going how do these not fit.

    From just Googling it it seems they are 37-540 but they were advertised in the ISO sizing so thats where the issue is. Seems from a quick reading of reviews online its a common problem that catches people out.

  • Registered Users Posts: 491 ✭✭Elvis Hammond

    The ISO sizing uses the BSD (520 & 540mm here), so you can't go wrong with respect to them fitting on the rim. (Wouldn't be much of an international standard otherwise.)

    It's the older fractional or decimal inch sizes based on rim + tyre diameter you have to be careful with.

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