Tyre sizes - what's the difference

Discussion in 'Beginners' started by gordonrobb, 8 May 2008.

  1. gordonrobb

    gordonrobb New Member

    Hi there. New to this thread, and pretty much to cycling to (after about 30 year break). Recently got rid of my old, heavy, full suspension monster and bought a 2007 Giant MTB. I don't intent to ever be hurtling down any mountains, but, being quite heavy myself, I like the feel of mountain bikes better. I mainly will be up and down curbs, and some light off road stuff.

    I got a punture (well wrecked the tyre on the back) and replaced it. the one that was on it was a 26x19.5 and the new one is 26x2.1. Here is my question.

    the new tyre looks much bigger. Is there any draw back in this? Will it use up a lot more energy to cycle, will it be slower, or does it not make that much difference?

    Looking forward to getting lots of usefull cycling info about lots of stuff at this site.
  2. John the Monkey

    John the Monkey Frivolous Cyclist

    There's plusses and minuses depending on what you use the tyre for - the best reference I can think of for this is this page on Sheldon Brown's site.

    If you're riding on roads, in general a thinner, higher pressure tyre with minimal tread is "better" - but there are lots of variables related to tyre construction etc that may affect that. I'd suggest reading the linked page, as it explains things far better than I could :smile:
  3. OP

    gordonrobb New Member

    Wow, thanks for the speedy response. I'll read up on this and see what it tells me. Thanks.
  4. Steve Austin

    Steve Austin The Marmalade Kid

    tbh it won't make that much difference on the rear of a MTB. it might drag more as its got more tread in contact with the road. might grip a bit better off road. Might grip better on fast corners off-road.

    TBH i would have the wider tyre on the front of my MTB as this helps grip when steering.

    All this assumes its the same sort of tread pattern, and its not dramatically different in structure, weight knob pattern.
  5. Paulus

    Paulus Getting older by the minute

    Hi there gordonrobb, a larger tyre will have more rolling resistance at the point the tyre meets the road because of the size. Therefore a smaller one will have much less and will roll alot easier and so faster. Also, a knobbly mtb tyre will be slower than a slick, treadless one . If you want to do mostly road riding have a chat to your LBS and get some duel purpose tyres. Good luck and welcome.
  6. 26x2.125 is the tyre size which mountain bikes inherited from 1920s american cruisers, the 26 refers to the outside diameter of a 26x2.125 tyre when installed on a wheel and the 2.125 refers to the width of the tyre when installed on a wheel. In inches.

    2.1 is the standard for dirt tyres although they range from 1.8 for light weight cross country whippets to 3 inches for big tough down hill bikes.

    Skinny road specific tyres are also available for 26 inch wheels which range from 1inch upwards and are identifiable by their lack of tread.

    The type of terrain you ride on will determine what kind of tyre you select, a proper, knobbly dirt tyre will be slow and sluggish on tarmac whilst a slick tyre designed for efficiency on tarmac will have limited traction off road.

    The difference between a 1.9 and a 2.1 is very little, a fifth of an inch or about 5mm, and bear in mind that its a nominal measurement, one manufacturers 2.1 might be the same width as another manufacturers 1.9.

    Other factors will have a greater effect on the performance of a tyre, inflation pressure, tyre weight, rubber quality and tread design all have a bearing.

    If you get really anoraky like me you'll end up with several pairs of tyres hanging in the shed for different conditions and you'll discuss different types of mud with your anoraky friends.

    Welcome BTW, there are some good folks here.
  7. OP

    gordonrobb New Member

    Thanks guys. Have decided to leave things as they are until I get a clearer picture.
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