I’m just in the process of choosing some Rims for a CX build, I’ve got a few options with internal widths of 14, 13, 19 and 21mm in the running.

There seems to be lots of contradictory advice on t’interwebz about regarding what widths of tyre you can use with narrower rims for CX/off-road purposes.

Some seem to be saying a 13/14mm rim should not have a tyre above 28mm fitted (2X rim width) others suggest 32mm is an upper limit based on certain tyre manufacturers literature, others seem to believe 35mm+ would be fine on a 14mm rim, while some seem to believe you should go wider and use something at the 19/21mm end of the scale

From MTB experiences I can’t really see why widths need to be so limited, is this a road hangover?

So I’m sort of errring towards unfashionable, narrower rims as they would save me both weight and cost… but will I be pinching a 32 – 35mm tyre all the time?

And then there’s the option of going tubeless… Hmmm.

Or am I just over thinking this?

Thoughts / Experiences?

I bought a flat bar hybrid with 14mm internal width rims, and I also have some Kinesis CX wheels with a 19mm internal width.

I honestly can’t notice any handling differences with either 35mm Vittoria Hyper (v large) or Kenda Small Black 32mm tyres running on the two rims.

Maybe rims and tyres are constructed better than they were when those tyre size charts were made??

FWIW, i’m just building some new wheels, and went with Alex ATD470 from Superstar (30 quid each 17mm tubeless ready)

are you racing or just riding about?

The current STW rule of thumb (for all types of bike) is that if your tyre isn’t square, your rim isn’t wide enough

FWIW I’m happy with a set of 29er Flows (old, not EX’s) with 35’s fitted. I have some narrower rims for 28’s. I don’t currently run any 700 sizes that aren’t 28 or 35.

Pretty sure that the practical advice last time this topic came up was that so long as the tyre was wider than the bead seat you should be ok if you like the way it behaved although there were many purists who bitterly dispute this.

The current STW rule of thumb (for all types of bike) is that if your tyre isn’t square, your rim isn’t wide enough

Yeah, but is it the end of the world if you break this “Rule” I mean I have various bikes with rims much narrower than the tyre and I’ve not yet died to death riding them…

Plus lighter wheels are beterer (so we’re told), as I see it one of the easiest ways to lighten my wheel build will be to use a narrower rim… right?

I run Challenge Limus and Griffos.. 33mm both and I’ve gone for 21mm rims. The spread of tyre is a little fatter and the knobblies seem to grip better in the corners. Pressures range from just 30psi through 45psi course/conditions dependant. Clinchers not Tubs too.

Does that help?

You’ll be fine. If you run them at low pressure, relatively wide tyres on a narrow rim may roll about to some extent, particularly at lower pressures.

14mm Rims ordered, the last two Velocity Razors from PX (@only a tenner each it was rude not to really)

So it gets to be a bit of an experiment for me I might as well get the wheels build and then worry about I’d have paid more for a pair of Rigida’s in 19mm or 21mm and they’d have weighed an easy 100-150g more each…

Think I’ll try going lighter weight all round then, possibly try taping them up to run tubeless so next question, what’s my best option for a general purpose tubeless ready CX tyre? say 32mm+?

Sheldon Brown’s site has got some useful information about this: http://www.sheldonbrown.com/tire-sizing.html

Scroll to near the bottom for a handy tyre/rim width table.

ye olde rule of thumb guide for rim/tyre width guidance: Sheldon Brown

EDIT – beaten to it!

Well based on that rule of thumb tabe at 14mm internal I’d say my chosen rim possibly squeaks it with a 32mm tyre?

But do the same rules of thumb apply when you start looking at running tubeless?

Vittoria XG pro tnt are pretty good.

But do the same rules of thumb apply when you start looking at running tubeless?

Only if you want to use the lower ranges of pressure, imo. If not then there’s not a lot of advantage to a wider rim. I’d go for more width over less weight every time, I value the softer tyre feel but I also bump rims now and then. 17-19mm seems about right for 35-40C, maybe 21mm for the 40s tubeless if I had the option.