Are deep section rims good for CX or not? Discuss...

othello

As the topic title says, are deep section rims good for CX, or are they more for style?

I would have thought lighter the better, and some well built low depth light rims (up to 35mm) would be better than 50mm carbon monsters. Thoughts?

imposter2.0

Disregarding the aero benefit (you're not going fast enough off road), the V-section is supposed to be better at mud-retention (or rather, not retaining it).

trek_dan

38mm seems to be the magic number of mud shedding versus lightness. I've been racing on Planet X 50's all season and compared to shallow rims definitely noticed less grass and clumpy mud wrapped around spokes.

VamP

There's no difference. But they look good.

tgotb

My experience is that 50mm carbon rims are *a lot* stiffer than Mavic Reflex (bog standard aluminium box section). This has the following advantages:
1. The wheels are easier to build
2. If you bust a spoke (for instance by standing on it - don't ask!) the rim stays roughly true, whereas the aluminium rim goes wobbly
The big disadvantage is that 50mm rims catch the wind much better when you're carrying the bike; I wouldn't use them for something like 3 Peaks.

Theoretically, the justification for deep rims is that, if the mud is deep and soft enough to close over a shallow rim, it takes more effort to suck it back out again (presumably lifting the mud as you go). This makes a lot of sense, but I can only think of two races I did last year that actually had those conditions for any significant distance.

Technically speaking, custom-built wheels using carbon rims are illegal, whereas shallow section aluminium rims are legal. In practice, this rule seems to be quite widely flouted at amateur level.

VamP

In theory I prefer the stiffer handling of the carbon rims as well, but by the time a 16psi tub has done it's wobbly best, there's no way you can tell what material your rim is made from in a blind test.

My current half way house has me with two carbon wheelsets for the fast half of the season (intermediates/file treads)and two alloy wheelsets for the muddy part (both with muds).

I find the better braking and durability and economy of the alloy wheelsets massively outweighs any ''performance'' advantages. Slightly different situation for those of you on disc brakes, but as TGOTB says the whole ''deep section is better in deep mud/sand'' narrative rather falls over when you look at the courses we ride. If it's even true in the first place. I've never noticed a difference.

tgotb

VamP wrote:

In theory I prefer the stiffer handling of the carbon rims as well, but by the time a 16psi tub has done it's wobbly best, there's no way you can tell what material your rim is made from in a blind test.

I'm not claiming to be able to tell the difference *on* the bike, but I was surprised how much easier they were to build. Just throw it all together, even up the spoke tensions, and you're very nearly there.

Even on occasions in very muddy conditions where I've alternated between a bike with the "right" tyres and one with the "wrong" tyres, it's surprising how little difference it really makes.

That said, for my last two wheelsets it only cost me about £70 more per set to use 50mm Carbon Farsports rims than it would have done to use Mavic Reflex. For me, it's worth £70 to save a couple of hundred grams and get more bling.

VamP

TGOTB wrote:

I'm not claiming to be able to tell the difference *on* the bike, but I was surprised how much easier they were to build. Just throw it all together, even up the spoke tensions, and you're very nearly there.

I was silently agreeing with that point, and then added a whole new point of my own I massively prefer the handling of my road bike on deep sections, so had thought that would translate to cross, but it just doesn't, due to the nearly flat tyres.

I think on the economy side, yes the Far Sports option is really good value , but I have experienced reduced durability compared to alloy in really tough conditions. This is mainly due to rim wear in gritty conditions, so not so relevant to disc brakes.