Rim size and tire width.
 

How does one tell the range of tire width that will work on a given rim?

There's plenty of latitude. I can tell simply by eyeballing, but folks who need numbers can refer to the charts put out by the tire companies. here's one.

Keep in mind that there's plenty of fudge room beyond the "recommended" range.

Over the last few years there's been plenty of published info about the implications of tires that are either too wide or narrow for the rims. If you have time to kill, you'll find plenty of reading search "bicycle tire width vs. rim width".

I've ridden a lot of miles with rim/tire combos that now know are so "wrong"! Especially big tires on skinny rims. (I guess I am a sick one. I love steep, rough downhills on very fat low pressure tires. Love the grip on turns. Apparently I've rolled them, crashed, woke up stunned and ridden on, completely oblivious. A bunch of times. And I am still clueless.

My current blasphemy is 35c Paselas on Mavic Open Pro and Open Sport rims with 60 psi, less if IU am going of pavement.

Ben

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<P>Can you give an idea of what you're working with?&nbsp; Keep in mind that the frame, the forks, and sometimes the braking system can limit tire size.</P>
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<P>Brad<BR><BR></P>

The best chart is at the bottom of this link:
https://www.sheldonbrown.com/tire-sizing.html

Do not trust manufacturers.

I have a set of wheels, inside width is 19mm, the manufacturer says any tire width of 28 to 62 mm. I have another set of rims with an inner width of 18.6, manufacturer says 25 to 38 mm. And another set of wheels at 19 mm inner width is rated by the manufacturer at 28 to 47 mm. All three of these rim widths are nearly identical and therefore have nearly identical tire ranges. But the manufacturers are all over the board for specifications.

I say again - do not trust manufacturers.

are the three rims identical in all other ways? maybe other
factors to consider other than just inner width.

height of sidewall?
amount of bead hook?
thickness of sidewall material?

The ability of the rim to resist the forces imposed by wider tires at higher pressures is likely the reason for the varying numbers given by different manufacturers, with the possible addition of varying levels of caution from that manufacturers legal department. With the usual caveats, I myself would pay attention to the numbers given by manufacturers, within reason.

I'm the same-- on my recent trip, the confidence I had going around corners on my loaded bike with 26x2in Supremes was.....supreme (apologies)

I know lots of factors come into play with cornering speed and whatnot, but I am convinced that the wider tires at the right pressures for the weight of the bike (ie, not too stiff, yet not wallowy) was the reason I was able to really lean on those suckers on good pavement and still allow for a good amount of suspension effect that allowed the bike to be reasonably settled over bumps.

I know we tend to "remember" downhills and going around corners as "faster and more dramatic" than it really was, but I was really impressed with out my bike handled around corners and compared to going around corners fast over the last few decades primarily on 28mm slicks, these 50mm (measure 45mm on my rims) very much gave higher grip and confidence in how the bike would behave mid corner.
There were times on this trip that going into a corner hot, I instinctively felt comfortable enough to slide off to the inside of the saddle a bit to get my body weight more down and into the corner--basically my old motorcycle habits coming into play, but I would never have done this if my "seat of pants" indicator was not telling me it was ok to do it.
I don't recall ever doing this on 28's, although I do suspect that I am better at cornering than 20 years ago--but I also suspect that in general, running lower pressures than I used to in the past has been an important factor in how my tires behave in corners and over bumps (even on an unloaded bike, with 28s, I run lower pressures than before and can corner faster and with more confidence than in years past)

Those factors do not come into play for tire wide.

Good discussion here.
Tech: Why wider rims will improve your ride - Mtbr.com

Switched from 38mm tires to 50mm Supremes for ride comfort but found that better handling & safety was the unexpected bigger benefit. Supremes roll fast, fairly light & no flats after 1 year. Actually I've noticed the resemblance to moto tires, heh.

The 50mm do feel slower than the regular marathon 1.5 I've had on another bike for years, but yes they do roll rather well. For a different situation I would have liked to try the Supreme 26x1.6 but not enough to spend up to 200 dollars to try them, and I had the 2's.