26" Rim Width

Eugbug

I asked this on a Facebook group, but didn't get a clear answer, so here goes again.
My 26" MTB rims are approximately 2 cm internal width. Are these classed as 1" or just like the diameter which isn't actually 26", do they go by tyre size? So is a 1.75" rim supposed to fit a nominally 1.75" wide tyre, even though the rims are approximately 1" wide?

Eugbug

So should I be looking for 26" x 1.75" or 26" x 1.0"? I want the same as what I have already (2 cm internal) and guides suggest those rims will take a tyre down to 28 mm width. Is a rim quoted as 1.75" actually 1.75" wide?
https://www.wtb.com/pages/tire-rim-fit-chart

JBA

Bike rims are a weird thing when it comes to measurements/sizes as they can and are quoted in a mixture of imperial and metric sizes.
Your rim probably has a 19mm internal width as this is a standard size.

Rim width and tyre width are not fixed ratios. On a 19mm wide rim you can fit anything from a 1.1" (28mm) up to a 2.35" (~60mm) tyre without any problems.

steve_sordy

The 26" refers to the outside diameter with the tyre fitted and inflated.
That was easy, but unfortunately tyres vary so although the "standards" (ahem!) apply all the time, stuff like outside diameter including tyre does not. Quite a few years ago now my mate and I both were riding 26ers and we both had Continental Trail King tyres (26x2.2 - with the black chilli compound). He then bought a new bike, one of those new-fangled 27.5" wheelers. The industry called them 27.5 because that was half way between 26 and 29 (what followed 26ers before the 27.5ers). Except that they were never 27.5, they were more like 27. But that sort of ruined the "Goldilocks" marketing proposition.

Once we'd been on the trail a while, I asked him if he could notice any ride difference; after all bigger wheels are supposed to roll better (mostly they do). He said that he hadn't noticed any difference at all. So, we measured the wheel diameters. My 26er was actually 26.75". His 27.5er was actually 27.25" diameter. Why so? He had Schwalbe tyres - Rocket Rons I think, fitted as standard. Whatever they were, they were lightweight and fast rolling, mine not so much. So, his tyre was 1/4" below declared wheel size and mine was 3/4" above! Only half an inch in diameter apart, no wonder he couldn't notice any difference in the ride.

When it comes to answering the question "what external width tyre fit what width rims (internal dimension)", then I haven't found anything better than this from WTB:

https://www.wtb.com/pages/tire-rim-fit-chart

Page down to section 3 "select tyre and rim width compatibility".
Scroll down to the second chart "mountain" and take a good look around.

You will find internal rim widths across the top, plotted against tyre width down the left. All in millimetres, so as tyres are sold in inches, you will have to do some conversions. Rims are sold in mm, see what I meant about "standards"?

If you have a rim with 19mm internal dimension, then Optimal Performance will be given with tyres of 47-52mm external tread width (1.85" - 2.05"). But Compatible Perfomance goes up to 62mm (2.44").
I once tried a 2.4" tyre on an 18mm rim, which is in the Not Suggested category. I didn't get away with it! On a hard corner, the rim rolled out of the front tyre and down I went. I was lucky not to damage the rim as well as me. If I had had higher tyre pressures I may have got away with it.

Eugbug

So is what I need (if it's quoted in imperial sizes) a 26" x 1.0" wheel if I want an exact replacement for my 19 mm internally sized rim? What I was trying to get at was whether it's possible that one inch width rims can sometimes be quoted as 1.75s because of the tyre that can be put on them?

JBA

Let's go back to the start: what bike have you got and what wheels (make and model) are currently on it?
That info will help us provide better information and suggestions.

steve_sordy

Eugbug said:

So is what I need (if it's quoted in imperial sizes) a 26" x 1.0" wheel if I want an exact replacement for my 19 mm internally sized rim? What I was trying to get at was whether it's possible that one inch width rims can sometimes be quoted as 1.75s because of the tyre that can be put on them?

No, rim widths are always in millimeters and they are the actual size. You can put many different widths of tyre on your rims (take a look at the WTB chart that I supplied a link for).

me-109

Just get a 26" MTB wheel or rim to suit whatever rim or disc brakes you have. They'll all be within a couple of mm of each other width-wise. It's only road bikes where clearance is that tight that you need particular notice. Or MTB wheel sizes you don't have, like 27.5+.