Lots of things to consider when upgrading wheels. First steep descents and carbon clinchers can lead to problems, especially if you are not very confident descending and ride the brakes or have some technical descents require frequent hard braking. The resin used to make the rims can reach the transition temperature to glass meaning it gets soft causing deformation or delamination of the rim. Neither of the are good! If your bike has disc brakes this problem is avoided!

For rim brakes, pro riders use tubular wheels which because they have the tire glued to the rim have a different construction with more material in the tire bed and brake track area and are much more resistant to this problem. Also carbon clinchers can heat up a blow the tire off the rim.

Mfgs have largely addressed these issues with today’s wheels however mountain descending frequently would be the one area which would give me cause for concern. Additionally, if your are a bigger rider that is a further concern as it necessitates higher braking forces.

Final thing with respect to mountain descending, wind particularly gusty crosswinds. Depending on your conditions, moving in and out of protected areas can with a deeper section front wheels can lead to considerable input to the steering of the front wheel. Zipp Firecrest wheels are designed to have the steering input from wind minimized however it is not eliminated.

Last thing to consider is the carbon wheels can give a stiffer ride than aluminum wheels. They are good at absorbing road buzz but in my opinion can be a bit less compliant over small to midsize bumps. So depending on the road conditions you ride on this may or may not be important. This can be somewhat offset by running 25c tires and dropping the pressure a bit.

I own several sets of Zipp carbon clinchers 303, 404, and 808 so I am not bashing Zipp or carbon clinchers for flat, rolling, or light descending but serious mountains**********

I also own own a pair of Dura Ace 7850 c50 wheels aluminum with carbon brake track, which have a more v rim profile and are terrible in the crosswinds when descending.

The wheels I ride for hill are Dura Ace 7900 c24, one of the best all around wheelsets I have owned. Lightweight for climbing but are very compliant over bumps and chip seal roads, aluminum brake track for solid braking and otherwise bomb proof wheel set. Yes spoke count is low but Dura Ace spokes are made of super high strength steel which allows them to be tensioned to double the amount of standard spokes.

Another wheelset to consider would be the Hed Jet+ series (many depths) aluminum rim carbon fairing, similar construction to the c24’s.

I am mostly a flat lander but have recently been spending time in the Phoenix area and have learned about what descending is all about, I can only imagine CO!

BTW I am currently about 230 lbs.