Mrdaner - 2009-09-08 1:31 PM So I take it that 26 inches is the outside diameter then. I agree, that's just stupid. I would have thought that 26 is the rim size.
oh, it's worse than that. 26" is nothing. There is no dimension on a 26" rim, wheel or tire that's 26 inches. It refers to the nominal outside dimension of the tire, but that's so obsolete no one even remembers what the width of that tire was.
There is another measurement: ISO, which makes a lot more sense, so of course we don't commonly use it. ISO for a common MTB rim is 559mm
(the actual diameter of the bead seat
). Thing is, your shop knows this; if you went in and said you have a mountain bike, and you want to put slicks on it, they should have known that 26x1 3/8 tires would not fit
(fractional size isn't all that common anymore, and every mountain bike I've ever seen has 559 ISO rims, except some new wheel trends, the sort of thing you'd know if you had
). If it were me, I'd be looking for a new shop; what if this was one of those situations where it sort of fit, but might give out dangerously at the wrong time?
here is enough info to make your head spin:
http://sheldonbrown.com/tire-sizing.htmlas with everything Sheldon Brown wrote, be aware that although there is a ton of information, he often forgets that bikes did not stop changing/advancing in 1971, so he is prone to talking about things that haven't been made in decades as if they are common.