How do I know my tyre size?

rossbarney2003
rossbarney2003 Posts: 167
edited March 2008 in Road beginners
Sorry for the stupid question, but i'm having trouble figuring out what my tyre size is on my bike.

I'm going to be ordering a training tyre for the trainer i'm gonna buy soon but need to know the size to order.

I looked at the tyres I have on my bike now and it says 700 x 250 on the side of the tyre as well as some other figures (I don't have a clue what they mean lol). I was going to buy the Continental Ultra Sport Home Trainer Folding Tyre from wiggle but the only two sizes it has listed are:

26 x 1.75 & 700x23c


Would any of those fit my bike?

Comments

  • Morpeth
    Morpeth Posts: 104
    700x23c is the one you want

    26 x 1.75 is a mountain bike sized tyre
  • Morpeth
    Morpeth Posts: 104
    by the way, your tyre probably says 700 x 25.0 (the 25 equates to the width in mm of the tyre), i could be wrong though

    Still the same answer 700x23c
  • rossbarney2003
    rossbarney2003 Posts: 167
    Morpeth wrote:
    by the way, your tyre probably says 700 x 25.0 (the 25 equates to the width in mm of the tyre), i could be wrong though

    Still the same answer 700x23c

    It def says 700 x 250 lol

    I always thought that didn't look right :P


    Thanks for you help :D
  • Morpeth
    Morpeth Posts: 104
    i am intrigued now... anyone care to shed some light on the 250?
  • Morpeth
    Morpeth Posts: 104
    could be the TPI (threads per inch) number, ie. density of threads
  • pw1brown
    pw1brown Posts: 243
    Probably 25C not 250. 25C is only slightly wider than 23C.
    My bikes
  • rossbarney2003
    rossbarney2003 Posts: 167
    pw1brown wrote:
    Probably 25C not 250. 25C is only slightly wider than 23C.

    so should I still go for the 700v23c?
  • Cunobelin
    Cunobelin Posts: 11,792
    THis is what is known asthe "ERTRO" number, in the format xxx-yy

    xxx is the diameter of the wheel and is fixed for that wheel

    yy is the width of the tyre and can be altered

    Both are measured in mm


    It is more accurate to use this than the statute 26" x 1.75" as the standard can be different 26" tyres can be 559, 571,584, or 590 mm in diameter (most mountain bikes are 559) a difference in diameter of over an inch!

    Full details are provided by the CTC:

    http://www.ctc.org.uk/DesktopDefault.aspx?TabID=3802
    <b><i>He that buys land buys many stones.
    He that buys flesh buys many bones.
    He that buys eggs buys many shells,
    But he that buys good beer buys nothing else.</b></i>
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  • Rich Hcp
    Rich Hcp Posts: 1,355
    rossbarney2003 wrote:
    pw1brown wrote:
    Probably 25C not 250. 25C is only slightly wider than 23C.

    so should I still go for the 700v23c?

    They'll fit fine.

    2mm narrower.
    Richard

    Giving it Large
  • rossbarney2003
    rossbarney2003 Posts: 167
    Thanks for all your help :D
  • Nuggs
    Nuggs Posts: 1,804
    My Roubaix came with 700x25C tyres - I think they're (assumed to be) more comfortable as they soak up more vibrations.

    However, I would also expect the rolling resistance to be higher...
  • DavidTQ
    DavidTQ Posts: 943
    Nuggs wrote:
    My Roubaix came with 700x25C tyres - I think they're (assumed to be) more comfortable as they soak up more vibrations.

    However, I would also expect the rolling resistance to be higher...

    Different tyre ranges can have a huge impact on comfort as well as rolling resistance. An equal impact to tyre size alone I think.

    In the last week Ive had 3 different back tyres on first a kenda kontender 700x26 which was pretty comfortable, goodish grip under braking and rolled okish (better than a hybrid :D ) that was skipped after 2000ish miles when I had two punctures in two days and I reliased one of the cuts went straight through the tyre letting the inner tube touch tarmac...

    As a temporary measure whilst waiting for tyres I had already ordered to be delivered I brought in a michelin dynamic, 700x23 It was definetely worse comfort wise and far worse under braking, it did feel lighter and rolled a bit better.

    Next up was the Continental GP4000s (700x23 again), but far more comfortable than the michelin, only slightly worse than the kenda 700x26 tyres, only really noticeable on the bigger bumps. (The michelin felt as if I had a flat over every bump :D), The tyre rolled better than either the michelin or the kenda and the braking seemed far better than both the other tyres.
  • rossbarney2003
    rossbarney2003 Posts: 167
    I bought the training tyre and double checked with the salesman that it would fit.

    The turbo trainer is coming on monday so I better find out how to change the back tyre in the meantime lol, cheeso i'm a disgrace to the cycling world.....:P

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