What is the best rim width and type for tubeless 33mm CX tires?

I am planning to buy a new wheelset for my cyclocross bike. I was wondering what type of rim to choose. I will mainly use the tubeless Challenge grifo tire with it. According to Challenge, the tires are optimized for 21mm inner rim width and approved for 17-25mm internal wide rims: https://www.challengetires.com/faq#can-challenge-tires-be-used-with-hookless-rims

  • Will the recommended 21mm internal width give the best performance or is 21mm just stated to stay below 33mm actual width and a wider rim would be better?
  • Would hooked or hookless be better? Will it change the ride feel or the actual width?

For testing purposes, I mounted the tires to an old 19mm internal width rim and also to a 24mm gravel rim. Obviously on the 24mm rim, the tire was much wider but felt a bit “square” and not as lively as on a narrower rim.

My goal is to get the best feeling and performing setup with the 33mm tire. I am not racing UCI sanctioned races so it is no problem if the measured width will be a bit more than 33mm. So, what do you think would be the optimal rim for my purpose? Go with the recommended 21mm or wider? hooked or hookless?

Thanks for your thoughts!

What sort of racing will you be doing? will you have multiple sets of tyres for different conditions?

It might be a better idea to use latex tubes. it allows you to swap between tyres much easier, and to run lower pressures. the low volume, low pressure of cyclocross doesn’t gel well with tubeless.

I would not go with hookless.

yes, different tires, but all will be 33mm challenge tires. I like the TL setup ad will stick to it, the question just is, what is the best rim setup for the tire.

I would not go with hookless.

Why not?

The few people I have seen race on hookless, which were the giant wheels, all have experienced the tyre burp all the air out, or the tyre pop off the rim during cornering in a crit.

I have ridden hookless on gravel, road and mtb. Never experienced anything like that.

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What do you do when you puncture during the warmup? you can’t put a tube in a hookless rim.

do you repair the tyre, then try and reseal? do you have spares of that tyre mounted onto another wheelset?

You still can use a tube if its a tubeless tire. However it would probably be fastest to use a plug or it seals with the sealant. So, no problem at all.
And the best way is not to puncture at all, for which TL is the best option anyway.

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I liked 22mm, but I needed to use 19 to make vittoria fit 33mm rule

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Sort of sounds like you’ve answered your question here. 21 recommended and 24 too wide, so 21-23 depending what you find. Probably preference for the 21 end of that spectrum, but I say up to 23 for two reasons - one is the Challenge website says all their tyres are now made to remain UCI compliant on up to a 23mm rim - you’ve said that doesn’t really matter to you but it’s an indication of their design thinking. Also, rims are getting wider rather than narrower, which means the next few generations of tyres are going to be optimised for wider rims too. So 21 might give you the best ride today and 23 might start to approach that square feeling, but 23 is probably also future proofed in terms of tyres for a while.

(As for how wide CX rims will go, my theory is they’ll keep going til they hit the 105% rule - even if CX is relatively slow, there’s still enough time spent on course at decent speeds for there to be some kind of aero savings by having a 33mm WAM tyre on a 35mm external rim which is 45mm-ish deep. Hard to say whether that will be a 30mm-ish internal rim width or if they’ll keep it in the 25mm range and then just mould extra carbon onto the rim like the current Roval Rapide wheels.)

There’s some confidence to be gained by having hooked rims if you have the option to go either way, but hookless interfaces are getting better and better so if your ideal wheel happens to only come in hookless I wouldn’t let that be a reason not to buy it. Tyre inserts could be a nice extra security feature if you buy hookless and end up having issues or feel unsure at any point.

In my experience, there’s no measurable difference in tyre width between otherwise-identical hooked and hookless rims - the difference is really just in the shape of the inflated tyre, and that’s almost too small to notice anyway.

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What pressure were you running the 33s at? Another issue if you go too wide is that the sidewalls start to get exposed as the tires is less bulb shape risking more sidewall damage on roots and rocks etc during races

At 77kg, I am running ~ 26psi with inserts.

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21mm was the max to fit under the gauges, but also much better stability wise than my 19mm rims. I ran a lot more pressure than your average UCI was at the time though (40+), so maybe others can get away with 22mm. This was true with schwalbe and spec. 33mm tires. I dont remember what I9’s internal was, but it made any of my i9 sponsored friends struggle with tires though the season, with the solution unfortunately being the 31mm vittorias, making for a very low volume tire.

Also worth noting, I ran hooked and hookless setups and never burped or flatted a tire. I thank schwalbe tires for that (except the file tread, that thing sucks.) I was running tubulars about half the time, and the same can not be said.

For what its worth, now that I am out of UCI, 35mm tires have made my life a lot better, and I can run normal human pressures, (with the tannus insert)

Also, I would not recommend squaring out the tire any more than you have to, but that might depend on the speed your riding, if you are riding at a pretty high level, you will be leaning the bike a lot, so a square tire can be a mess, especially with the common occurrences of off camber in CX. On the other hand, for some riders that arent as comfortable getting the bike leaned over as much, you could argue for a square profile.

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I cant comment on rim width…but I can say tubeless is fantastic, and low pressure is not a concern. I’m 185 lbs, and have only experience a single burp…a front tire mid crash when the tire slammed into the ground sideways after being airborne. I’ve gone as low as 20psi with no issues.

I went with CR 1600s as they seemed like a great value and I’d heard some tires measure >33 with 23mm inner width, the CR 1600s have a 22mm internal.

With the low pressures (compared to volume) in cross tires I’m betting you would. Another vote for hooks for me.

I ran a few psi too low in a gravel race last summer and burped both front and rear on a technical descent until they were nearly flat (on hookless rims).

Cross has you cornering with the wheel turned at really aggressive angles, and often overdoing it and crashing or nearly crashing. I’ve ripped glued tubulars off a rim. I’m sure hookless would have failed in that scenario as well. Decent chance hooked tubeless would hold.

have you tried hookless? I’m 215lbs, and was racing at a reasonable high level and have not burped on a hookless setup.

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This could be just a case of one persons wheels and tyres not being as tight fitting as another.

I remember having lots of trouble seating my challenge tyres as they felt loose on the rim, and anytime I raced tubeless I would lose half my pressure mid race.

Probably true. The burping I’ve experienced with hookless is due to the tire bead being pushed briefly into the center channel I believe, and there’s no reason this couldn’t happen with hooks I guess.

I still think hookless at 20psi with a 33c tire might be an unnecessary risk.

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On the tubeless thing…2 things.

1 - the fit is SUPER important. I set mine up so tight that they hold air even when the bead is pushed all the way into the center channel. You can test this pretty easily by just putting 10psi or so in, and just mashing the side of your tire with your thumbs sideways.

2 - just get foam inserts. Pretty much eliminates all of the paranoia and downsides of tubeless…plus I understand there are some ‘suspension’ benefits as well.

I use 23mm internal and my pdx 33 tires measure closer to 34/35, chicanes on another set of 23mm internal wheels measure at 33/34.

Challenge htlr tires are specifically approved for hookless, Donnelly pdx aren’t marketed as such, but I have confirmed with them that they have been tested and work, as well as a season of racing on them that they work on hookless

both are mounted on hookless rims, had no issues with either burping last year, and I had a few races in the mud that I ran closer to 20-22psi without issue. I’ve easily ran tubulars that low, was hesitant on tubeless but it worked peachy.

I recommend against tubes. Throw some inserts if you want the extra protection.