Very dumb question about tyres

Mattonabike1
Mattonabike1 Posts: 4
edited June 2008 in Road beginners
Greetings all,

My aplogies for what will be the stupidest question you will hear today.

I've got 26 x 1.75 tyres on my bike at present (Thorn Sherpa) and am looking to change to new tyres. My dumb question is that will 26 x 2 tyres fit on my bike?

Worth pointing out I'm not educated on tyre sizes and any answer is wholeheartedly appreciated!

Comments

  • Audiolathe
    Audiolathe Posts: 6
    Well tyre size is as closely linked to wheel size as it is to frame size - in theory it should be possible to fit the tyres you describe, but as I'm not familiar with the frame you mention or the rims it comes with I cannot say for sure there will be enough clearance between the frame and wheel at the crucial points like front fork and seat and frame stays. Easiest is to ask a bikeshop for advice I would think.
  • Mattonabike1
    Mattonabike1 Posts: 4
    Thanks Audiolathe, your reply has at least made me feel like I'm not as dumb as I though I was.

    I'm looking at gettng Marathon XRs and am positive these are the ones I want now.

    Whilst I'm here asking dumb questions I may aswell ask something I've never fully understood - why are some tyres marked as 26 x 1.75 and some as, for example, 700 x35. What do these ammounts stand for?
  • CrookedCucumber
    CrookedCucumber Posts: 324
    It's just metric and imperial. 26x1.75 is 26 inches diameter by 1.75 width, while 700x35 is 700 mm diameter by 35mm width. 700mm is about 28 inches.
  • John Stevenson
    John Stevenson Posts: 962
    700 and 26 are the outside diameters in millimetres and inches respectively, of the original size of the tyres that gave rise to the rim size that's now commonly associated with those numbers.

    Confused? You should be. It's a mess.

    700C originally had a quite fat tyre on a rim 622mm across at the bead seat. These days the rims are still the same size, but tyres can be anything from 19mm ro 50mm in size.

    Similarly the mountain bike '26in' has a rim 559mm across, but the tyres can be anything from 1in slicks to 2.7in downhill monsters.

    700A and 700B have vanished and 700D was a short-lived experiment by GT back in the 90s, but there are still several different '26in' wheel sizes around, none of which are compatible with 559mm mountain bike rims.

    The legendary Sheldon Brown has far more: http://sheldonbrown.com/tire-sizing.html
    John Stevenson
  • lateralus
    lateralus Posts: 309
    at the risk of information overload, tyre sizes that start with "26" fit the standard mountain bike wheel size. Tyres that start "700" fit the standard road bike wheel size.

    You are looking at going from a 26x to another 26x, so the new tyres are the correct rim size. As pointed out above, the only potential problem is that the second number (i.e. 1.75 or 2) means that the new tyres are a bit wider than the current ones.

    Have a close look at your existing tyre and see how much clearance there is around brakes, mudguards, etc. If the clearance is tight, you might have issues switching to a wider tyre.
  • blorg
    blorg Posts: 1,169
    edited June 2008
    Be very careful, as there are two (in common circulation) different "26s" with completely different bead seat diameters. The decimal ones (e.g. 26 x 1.00 through 2.3) are 559mm (this is the standard MTB size and what you need) while the fractional ones (e.g. 26 x 1 3/8 ) tend to be 597mm. This is all detailed on the Sheldon Brown link from John but it bears repeating, in case you might think that 26 x (a fraction) would work - it won't!
  • Mattonabike1
    Mattonabike1 Posts: 4
    Thanks for the help guys - I'm glad I asked! :shock:

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