hey there we did an article on this in Issue 7 re: sand that revealed at speed the rim profile doesn't matter, and if you get offline a deeper rim can make handling funky. at very slow speeds, things change - but we didn't test that much.
regarding mud, we also have a very interesting article on this in Issue 13 on mud and rim profiles. I think you'll enjoy it and learn something - I know I did in taking part in the testing. sorry we can't give it away yet!
stay tuned, or subscribe to the content-packed print mag if you haven't yet! it's less than one entry fee for four content-packed issues!
~20mm is great, light fast and handles superb, mud grass can build fast around nipples/rim and add a lot of rotational weight.
~30mm is an awesome all arounder and less chance of buildup in mud/grass
~40mm you should consider carbon, alloy will be too heavy. Plus, carbon would weigh as much as the ~20mm rim profile
~50mm you are not neils albert nor sponsored by edge composts
I used a EA70x rim which has a 28-30mm depth, it was light, fast and worked well on MANY course conditions, it was better for the Pacific Northwest mud.
09'-10' season, i used a reflex, it was light but the wheels gained A LOT of weight at the Sedro Wooley Seattle CX race and Marris Farms. Other than that, they were baller.
Does Albert still ride deep rims? Or has he ever? I know recently I haven't seen him on anything deep, but haven't really looked carefully. It's actually of interest...
Shoot, you caught my bluff. A rad video nonetheless.
The trend I saw last season while at the World Cups, Super Prestige and GVA's was that almost everyone at the top level was in the 40mm range on carbon for rim depth. My option is that this is for the stiffness of the rim depth and the weight savings of the 40mm(ish) rim verses a standard alloy rim or a 50mm aero rim. The Zipp 303 and the Shimano C35 were the most popular style of rims being used. (I saw Niels on the C25's several times, so it's not all about the depth). I'm think the deeper rims help in very sticky peanut butter mud to keep them from self-propagating more mud on mud (Koppenberg cross comes to mind). That said, exposed nipples at the rim like to catch grass (but I still prefer them because hidden nipples are a pain in the a$$ when you need to true a wheel) and tend to help with the mud build up.
For my money a 38mm carbon rim built up on CX-Ray spokes and solid hubs (performance over weight) is ideal. The stiffness and weight of the 38mm rim will be great for constant accelerations and strike a nice balance between stiffness and weight for most riders.
Actually Albert told us that he preferred the low rims for races, and they were lighter, so he used them pretty much universally and doesn't like the stiffness of taller rims.
you can read our interview with him here: Ask a Pro with Niels Albert
but because Shimano is doing away with the 25 he'll move to the 35mm because he has no choice for next year.