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Need help with tyre sizes

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  • 29-08-2014 6:45pm
    #1
    El Kabong!
    Registered Users Posts: 296 ✭✭


    I have 4 mountain bikes in the family and I want to change the tyres from knobbly to road.

    I can't see any markings on the rims, but with a measuring tape the all seem to be about 28mm on the outside edges.

    The tyres are as follows:

    24x1.95
    26x1.95 (x2)
    26x2.1

    I need to understand the best road tyre size to go of each of them.

    28mm is 1.1" so I am thinking I can go for tyres that are just above that width, or even 1 3/8, as that seems a popular size.

    So can I just go and get 1 set of 24x1 3/8 and 3 sets of 26x1 3/8 or should I go even narrower???

    Or do I need to think further and check beads etc?

    3 of the bikes are just Halfords/Apollo and another is probably a step higher but not much.


    Thanks.


Comments

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    #2
    Al Wright
    Registered Users Posts: 167 ✭✭Al Wright


    Here is a link to an explanation of tyre and rim sizes on the CTC (UK) web page;
    http://www.ctc.org.uk/cyclists-library/components/wheels-tyres/tyre-sizes

    I think it is a case of choosing the most popular size tyre available in your local shop, the sizes are likely to be 26 x 1.5. (too narrow a tyre on wide rims do not roll properly on cornering)


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    #3
    Type 17
    Registered Users Posts: 2,730 ✭✭✭Type 17


    Bear in mind that 26 x <decimal width>, e.g.: 26 x 1.5 is an entirely different tyre size than 26 x <fractional size>, e.g.: 26 x 1 3/8.

    For clarity, you should compare the ERTO/ISO sizes, in the left column on the CTC webpage referenced above, which are in the format (e.g.) 40-559, the 40 is the width in mm, and the 559 is the diameter of the rim at the bead (where the rim meets the tyre).

    559 is the size that you'll want for mountain bike wheels - any tyre sized "<any width>-559" will fit, but note that maximum pressure increases as the width decreases, and higher pressures mean lower rolling resistance on the road (which is the main reason to change to road tyres on an MTB)

    I have a lovely 1991 MTB with 25-559 (26 x 1.0) tyres that take around 8.2 bar (125PSI) and it flies along like a road bike - brilliant town/commuting bike.


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