drummergeek

Hey guys,

I know about the internal rim width measurement for tire sizing, but how come that internal measurement never seems to be used on websites when I want to buy a rim?

For example, I recently bought a rim listed as 700c x 35 rim for a hybrid bike. It worked well for the 32mm tires I had. Where are they getting this "35" number? Even the outside measurement of the rim width was only about 25mm.

I measured my current road bike rims that I have 25mm tires on, and the external width was about 20mm.

I need a new rim for my road bike, so last night I ordered a rim listed as 700c x 20. I want to be able to put 23's or 25's on this rim, so I should be ok I think?

I'm guessing that merchants list rims according to the average tire width that would go on them?

cny-bikeman

The measurement that you cite is indeed a convenience measurement to indicate what the manufacturer considers is the optimal tire width for that rim. There will be a fair amount of slack so tires larger or smaller in width will still work. In many cases you can find the actual internal measurement with a Google search for specs or from the manufacturer website. Sheldon has a good discussion and chart for suggested rim vs. tire width - Width Considerations (well down on the page).

Andrew R Stewart 

Not every supplier feels the need to provide every/all details on every product they list. You can vote for their choice, how much information they list, with your money and purchase or not. Andy

Bezalel

Unfortunately the term "Caveat Emptor" applies when purchasing rims. You need to determine if the advertised width is of the rim or the suggested tire, this can often be determined by reading the description. What is harder is determining if the width is the overall rim width or the ETRTO width.

techsensei

Tire sizes are often wrong anyway. Just the other day I mounted a tire labeled as a 700 x 23, but they were only 20mm wide.

I'm sure the rims you ordered will work fine with 25's.

mulveyr 

It's not necessarily the case that they're wrong, it's just that the width is simply an approximation; the final tire width depends on the rim and pressure. I have a set of tires marked 700x38, for example, that are 35mm on one set of very wide rims, and 38 on another.