Deep rims or shallow rims for cyclocross?

[nickcube]

In the middle of planning a new wheel build using chinese carbon clinchers, disc brake.
I'm just not too sure if I want to go with 35mm or 45mm for the build. The courses I ride are usually pretty twisty, stop/start type of courses and not a lot of straight flat sections to power down(I'm in australia).
I'd like to run 45mm because I can and, well, #aero. What are people's thought on the whole wind up/ getting up to speed thing faced with deeper section wheels? Is it true and does it matter for cross? or would I be better off with the supposedly faster accelerating 35mm? on a side note I'll be using these wheels in the summer on fairly flat rides
Any input would be awesome

[stormur]

The only truth about high profile in CX is it carry bigger logos at races .
favorite profile of Nys was 35mm, but Shimano contract forced him to ride whatever Shimano wanted ( there's interview somewhere in web ) , other Belgians (pro) opinion about rims : lighter=better ( even24mm ).

if I would build cf wheel set for cross ... 30mm max would be my choice. 24 spokes front, 28 rear.

Aero ? really ??? in CX wheels???

[Exar]

I have a couple of sets between 58 and 20 mm and like the 20mm's best, because they feel almost effortless to get up to speed. However looking at my last cross race there were a couple of sections where I was going over 40 km/h, taller rims should provide some aero benefit there. If your races are only twisty-turny without any high speed pedalling sections, I'd go for the lightest rims you can get.

[jcrr]

There should be a choice in the poll for either <30mm or 24mm.

@Exar- You are in overall agreement, and also bring up the argument of some races with very high speed sections. I guess it depends on where people live and what their racing conditions look like, but it would seem to me that over the course of a CX racing season, the number of times a taller rim would be advantageous would be small compared to the where a shallow rim would be king.

[wpccrunner]

I personally would go for the lighter weight over the aero for cross racing. How much aero gain can a 45-50 mm rim be with a wide cross tire mounted. It comes down to the whole debate of the tire/rim interface to reduce the turbulent air as it flows around the tire.

Technically a deeper wheel could be built up into a stiffer platform wit the different spoke bracing angles.

[euan]

Cyclocross is all about surges of power, go for lighter over aero every time

[Gazelleer]

I thought the high profile rim were used to slice through mud instead of completely be drowned and covered in deep mud?

[jcrr]

Deep rims acting as rudders in mud or sand are a myth.

Due to the constant accelerations, carrying the bike, etc, shallow lighter rims rule.

[stormur]

I have somewhere short movie made on cx competitions ( wet mud ) - showing how racers "jump" to throw away mud from high profile rims... and also riders on low profile rims which do not do that



About what wheel stiffness we talk being on approx. 1.4 bar ( race tubulars ) ?

[Exar]

Yeah wheel stiffness becomes a moot point once you wrap your wheels in 1.6 33C cotton tubulars and ride them offroad... If you feel any flex how could you pinpoint the source?

[Asymptotic]

Agree with advocates for shallow light weight rims. Even on a rare course where you might have a flat 600-800m straight the aero benefits over 2-3 minutes for say a 50mm rim are non-existent compared to a 20mm rim

[MMMhills]

I like both 24 and 35. the 24 are lighter for all the acceleration but the 35 are great for very muddy courses or courses with long straight aways. they do hold less and shed more mud.

[spookyload]

From your description, I would go low profile and wide. Yinshun has a 29mm wide rim that is sweet and light. It is 33mm tall, but wide is what you want. This of course is assuming you are riding clincher and tubeless. Twisty and power surges scream stout wheel set. With wider, you gain all sorts of footprint from the wider stance of the 33mm tire, plus you are increasing air volume so you can run lower psi if you choose. They are hook beaded rims so no issues with blow offs at higher psi. I swapped over to Reynolds 29mm wide rims this year and they are amazing. Granted they are the mtb 29er rims, so I have to swap out hub parts to make them work, but they are light and stiff.

[Multebear]

The only truth about high profile in CX is it carry bigger logos at races .
favorite profile of Nys was 35mm, but Shimano contract forced him to ride whatever Shimano wanted ( there's interview somewhere in web ) , other Belgians (pro) opinion about rims : lighter=better ( even24mm ).

if I would build cf wheel set for cross ... 30mm max would be my choice. 24 spokes front, 28 rear.

Aero ? really ??? in CX wheels???

Noboby claims, that deep section rims in cx are for aero benefits. Deep section rims are for very muddy races, where you don't want the mud and sticky grass to slow down your wheels to much.

Surely weight is more crucial in cx than any other cycling discipline. But on very muddy courses, deep section might prevent too much mud and grass to pack between the spokes. It's better to cut through the mud than sinck into it, and shovel it with you, which will make the wheels considerably heavier.

BTW Wout mostly rides 303's, they are 46 mm.

[the_marsbar]

Do you race CX? I don't think it makes much of a difference. I've never seen mud being "shovelled" as you say. I'm raced for several season, and we get thick mud here as well...

I think "if Wout rides it, it's the best" is a poor argument. First of all, you don't even know if (and in that case what) he's told to ride any particular equipment. I'm sure he'd win on 202s as well.