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Reading tyre size

Discussion in 'Riding Gear and Bike Accessories/Parts' started by Danhendo888, Apr 30, 2014.

  1. A quick noob question,

    What do the numbers below mean with regard to tyre size on a motorcycle?
    Rear Tyre: 140/70-17
  2. 140 = tyre width, 70 = profile height, 17 = wheel size
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  3. 140 mm = width, 70 = hight of tyre expressed as a % of the width and 17 inch wheel size
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  4. thanks a lot guys
  5. As above, but it's also worth pointing out that the width, and to a lesser extent, the aspect ratio figures are nominal rather than exact. Two tyres with the same numbers but from different manufacturers or model ranges can vary significantly when actually measured. Rim diameter is actual though, and is measured to where the tyre bead actually seats, not to the outside of the flange, which will be nearer 18" for a 17" wheel.
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  6. This becomes important if you are running tyre huggers and front fenders as they usually sit close to the tyre.

    Some brands make taller/pointer profiles and they can rub on the bike.
  7. Tyre diameter grows significantly with speed too. I've seen more than one close clearance mudguard either burst or worn through from the centrifugal expansion of a tyre :eek:.