Strange tyre sizing anyone seen this before ?

[BADGER.BRAD]

O.k not really a commuter issue other than the fact I've put these tyres on my commuter bike. A friend at work gave me some MTB tyres that he had found In a skip about a year ago which I hung up with the many others which aren't really suitable for commuting or serious MTBing but I've always kept as spares for myself or anyone that wants them. I decided today that I would actually use them (rather than store them forever) to replace the very worn tyres on my 26inch wheeled Hybrid which I use as a commuter and general hack The tyres rather than being marked as 26x 1.75/1.95 or so are marked in mm giving both width and height ie:26x44/55 has anyone ever come across this before ? I know 700c tyres are marked with a width but I've never seen anything like this on a 26 inch wheel !

 

[addictfreak]

This might explain

http://www.wtb.com/tech-gms/

 

[mickle]

Beat me to it.

 

[ufkacbln]

Still unreliable though as the 26" tyre can have a difference in diameter of some 30 mm in diameter, and not fit some rims.

The CTC guide to tyre sizes gives examples.

If you can always go by the ISO number which is in t he formay of xx-yyy

yyy is the diameter of your rim, and xx is the nominal width of the tyre

SO long as the yyy is correct you can guarantee a fit

 

[mickle]

Still unreliable though as the 26" tyre can have a difference in diameter of some 30 mm in diameter, and not fit some rims.

The CTC guide to tyre sizes gives examples.

If you can always go by the ISO number which is in t he formay of xx-yyy

yyy is the diameter of your rim, and xx is the nominal width of the tyre

SO long as the yyy is correct you can guarantee a fit

Eh? This (26x44/55) is Wildnerness Trail Bike's attempt at making sense of mountain bike tyre sizes. All tyre size systems tell us the (nominal) diameter (26") and the casing cross-section (44mm) but only WTB tells us the width of the tread (55mm). Important information if you want to know if a tyre will fit in your frame or not.
Though it's been around for more than a decade only WTB actually use it to my knowledge, which tells us that other manufs. - and consumers - aren't that bothered.

 

[BADGER.BRAD]

I got the wrong end of the stick presuming that they were using a system similar to motorcycle tyre sizing one number being the width of the casing the other the height from the rim as a percentage of the width . In the case of the tyres I have, the two measurements match width of casing and height from rim exactly! Just chance I guess. I can understand this as on my on off road motorcycle I have to be carefull about rear tyres as the width size of the tyre is casing not including studs.
Thanks all for the replies.

Brad