tyre sizes - confusion about widths

fatfreddy

Hi all

can someone please explain tyre widths? I have 2 tyres apparently the same size - but different widths; 26x1.75" marked as 42-559 and 26x1.75" marked as 47-559. (Just to add to the confusion I also have a 26x1.95" marked as 47-559).

I understand the 559 bit but I don't see how 1.75" can be both 42 and 47. A straight conversion shows that 1.75"= 44mm. Could some knowlegdable person enlighten me?

thanks

FF

formerlyknownasbonj

see
http://www.sheldonbrown.com/tire_sizing.html
from that, a 559 would be 26" by anything from 1.00" - 2.125".
559 is the bead seat diameter, i.e. the (radial) size of the rim it will fit onto. As sheldon says this is the critical measurement.
42 and 47 is the flange width, i.e. the (lateral) distance from one bead to the other. It's probable your tyres are as such (cross sectional) (excuse sloppy ms-paint drawings):



in practice though, the 42 and 47 doesn't matter as much as the 559 - i.e. i'm guessing they will both fit onto most MTB rims.

fatfreddy

thanks for this

FF