nfhabit01

Hello all,
I am currently working on building up a new gravel bike that can be used for gravel riding, light single track, touring, road biking, and about anything else in between. Right now, I am planning on using a 650b wheelset with wide tires for gnarly stuff, and a 700c wheelset for more road oriented rides. I've started looking into different wheelset and tire combinations and I am starting to get a little confused on a few different things. Mainly, I am wondering how narrow and how wide a tire can be on a given rim. For example, could I run a 700 x 28 tire on a rim with an internal width of 24 mm or would that be too narrow. Also, how wide is too wide?

mstateglfr 

Yes you can use a 28mm tire on a 24mm internal rim...though that seems like the rim would be pretty heavy, being that wide internally. The outer diameter shouldnt exceed the tire width- that is something to consider too.

ckindt

The outside diameter exceeds the tire width on all of my wheels.

Emilio700

Road wheels were 17-18mm internal width for decades. Only now are 21-23mm internal becoming the norm. Gravel wheels 22-25mm internal width. Add 2-3mm if you run hookless beads although they won't allow pressure much past 60psi safely.
Any tire you might want to run will work on any wheel, don't overthink it. When going with tires wider than say 32c, you will get better handling, shock absorption with internal widths above 22mm.

I run 23mm internal hooked bead on my gravel bike with 700c tires. I run anything from 28c GP5000 @ 75psi TL to 40c Ramblers at 35psi on those wheels.
I think running 28's on a 24mm internal rim is fine but you'll find the rolling resistance of the same model in 32c is pretty much the same. Just a few grams more weight and aero drag but who cares unless you're racing. I'd suggest just running 32's for road. You'll be surprised at how fast they are. Drop pressure to around 45psi for crap surfaces and crank them to ~65psi for good surfaces.

Koyote

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

tFUnK

No such thing as too wide for me; I'll take whatever the frame/fork constraints allow. 25-28mm for my road frames. 40-42mm for my cx/gravel frames. 2.1-2.2 for my 26er MTBs.

chas58

you can google ETRTO chart to get the official chart, but a good version of that is in this link. That determines what is an approved tire size for a rim.


ETRTO tire wheel chart

chas58

Yep, the outer diameter should be less than the tire width.

I've used one (28mm) on a 22id rim (28mm OD). Rim was a little too wide. I ended up riding on the sidewall too much and wearing out the sidewall. Generally I would keep the outer width of the rim bigger than the tire to prevent this - and of course protect your sidewall from punctures.

msu2001la

Wide tires generally fit fine on narrower rims (within reason). I've been running 33mm cross tires on alloy wheelsets with 17mm internal/21mm external for years and never had any problems with this setup.
Shimano's Dura Ace (WH-R9100 C24) wheelset, for example, has an external width of 20.8mm and their recommended tire sizes are 23-28mm.

A 24mm internal width is a fairly wide rim. 28mm-32mm tires should fit fine on it. You can likely go much wider and not have any issues. You may run into issues if you try to run tires narrower than 28mm on that rim, though I'm not sure why anyone would want to do this.

Some of the confusion on rim/tire width comes in when people start talking about aero benefits. While wider tires generally fit fine on narrower rims, the aero benefits of a deep section rim are diminished if the tire is wider than the outside rim width. Zipp's 303 Firecrest carbon clincher (disc) has an internal width of 21mm, and an external width of 29.9mm. This rim was designed to be optimized around a tire that measures 28.5mm wide when installed and inflated. This is the "105% rule", where the optimal aerodynamic benefit is obtained when the rim width is 105% of the measured tire width. This is a completely different conversation than "will it fit". You could easily run much wider tires on a Zipp 303, it just won't be as optimized for aerodynamics.

chas58

I"ve been running 32mm tires on a 12mm internal rim. I was kinda pissed when I ordered built up the rim and realized how narrow it was. Certainly it isn't great at the extremes of pressure (too high may put too much stress on the rim, too low makes the tire a little squirmy).

msu2001la

It's interesting to note that rim width plays a big factor in how wide the tire actually is once it's installed and inflated. On a very narrow rim like yours, I suspect those 32s are actually measuring smaller than that. Below is a photo showing two identical 23mm tires on two different rim sizes. The one on the right is mounted on a rim with a 15mm internal width, and the other is mounted on a rim with a 20mm width. The one on the right has an actual width of 22.5mm; the other one plumps up to 25mm:




Cycling Tips has a good article on this topic, which is a few years old now but still relevant.
https://cyclingtips.com/2016/11/the-...e-road-wheels/

It's also interesting to note that (as of 2016) Mavic was stating that 25mm tires are the smallest that should be run on a 17mm internal width rim. and 28mm tires are the smallest that should be run on a 19mm internal rim. I will say when I first got my Ultegra wheelset 6 years ago (17mm internal width) I ran 23's on it with no problem, but found 25's at a lower pressure to be much more comfortable. I now switch between 28mm road tires and 33mm CX tires on that same wheelset and both sizes work great.

justcynn

good info! thanks