What does it mean when the width is written on the RIM?
 

I see some 26” wheels, they are rated 26x1.5 or 26x1.75/2.125 etc, this is written on the rim. Measuring the internal width of the rim is usually less than the stated number and even putting on a tire the width can vary a lot, for example a 26x1.5 rim can take a 1.5” wide tire or wider or thinner (according to sheldon brown’s chart and my own experience too). So what is the reason for the second number in the 26 x X.XX when it is written on the rim? And why do some rims have two numbers after the x, for ex 26x1.75/2.125?


http://i.imgur.com/Eodgag3.jpg

It means the rim manufacturer wants to be precise as to rim stats. It makes it a little easier to know what size tire is
optimal, which referring the doubly numbered rims, the tire sizes the rim maker feels the rim is suited for.

I'd say 1.5 Minimum, wider , since its an MTB, is fine... ETRTO is the rim bead seat diameter standard
also indicating a common MTB tire matching that number..




'/,

Back in my bike flipping days, I've seen rims marked 1.5 that was wider than one marked 1.75.
Either would be totally fine for a 1.25" tire.

Straight answer - next to nothing.

The 559 is the important number.

The important measurement is the inside width, which may or maynot have any correspondence with the numbers on the label.

I want to say that when a rim width is listed with ISO or ETRTO nearby, it's the inner width. But I'll welcome corrections. :)

I disagree WRT the example given and the common experience of tires of vastly different widths being OEM speced on rims with this "1.5" label. (Note I said "label" not dimension or size). If fact it could be said that having a tire reference on a rim is misleading.


Back in the beginning of the MtB movement we (the USA) had various import tariffs on bikes and parts (IIRC it was the industry group known as BMA/6 that lobbied and attained said tariffs). These tariffs used the dimensional language that was in use by the US manufactures at that time. So 26x1.75, 26x1 3/4, 26x2.125 were all the spec that triggered a tariff. So the foreign manufactures simply changed their labeling of some parts to end up with a work around of the tariffs. These different labels caught on by the buying public (if for no other reason then the need to believe their non US made bike was better and unique then the gas pipe stuff the US mostly made).


Is this what really happened? I have never had a manufacturer industry insider or a government employee confirm this but I have heard this story from a number of supply side and retail sources over the years. Andy.