Bicycle Mechanics - How wide of a tire can go on a 20mm rim?

Let's assume bike geometry, cantilever clearance, chainstay, seatstay and all that is a non-issue, how wide of a tire could you go on a normal 20mm 26" mountain bike wheel. Not a deep-V or tubeless or anything special, just a plain old cheap wheel.

Check out the chart:

http://sheldonbrown.com/tire-sizing.html

Let's assume bike geometry, cantilever clearance, chainstay, seatstay and all that is a non-issue, how wide of a tire could you go on a normal 20mm 26" mountain bike wheel. Not a deep-V or tubeless or anything special, just a plain old cheap wheel.

I've got to know: Why do you ask?

Always before on mountain bikes I've just kind of assumed that the tire/rim interface was the irrelevant factor because one or more of the things that you excluded (you forgot front derailleur clearance) is always a limiting factor.

There's got to be an interesting story behind your question.

Did we have another rim self-destruction from using too big of a tyre with too much pressure???

Check out the chart:

http://sheldonbrown.com/tire-sizing.html

as Sheldon says this chart is a little conservative and would suggest a maximum of about 26 x 2.0 for this rim. However many MTB´s come with wider tires on narrower rims as standard. In my opinion the limiting factor to tire width is more often the frame/fork and not the rim (edit of course as Danno notes the rim has to be strong enough to take the pressure and the manufacturers info should be checked).

This is on my cross bike but I have 40mm tires on Sun M14a rims. I believe they are only 19mm wide. Roger

I'd like to know how narrow a tire I can fit on a 26 x 1.50 rim, but I'm not all that anxious to strip the current tire and tube off the rim just so I can get an internal measurement.

Anyone have enough experience to save me the job?

I've got to know: Why do you ask?

I'm thinking of going with a wider rear tire for my snow contraption. I'm currently on 1.75" knobbies, and given the clearance I'm seeing, I could probably get away with 2.25" but I'd probably go with 2" wide tires just in case the wheel goes a little out of true for some reason.

I didn't know if 1.75" was the max, though, without going to a wider rim. 2" should be fine.

as Danno notes the rim has to be strong enough to take the pressure and the manufacturers info should be checked

Since this will end up being my snommuter bike, I'll probably run at the minimum pressure rating for the tire (40, 45 PSI or so) Lower pressures get better traction in the snow.