You want to go for aero wheels but unsure which depth to go for?
All depths of rim over 38mm will offer an aero efficiency advantage at 18mph+ The deeper the rim, the greater that advantage.
Let's consider a comparison of all the models. This is true for tubular and clincher rims:
38mm will have a weight advantage for climbing in comparison with a 50mm or 60mm rim but they only start to create aerodynamic efficiency savings over 18-20mph. They are a "lumpy" stage choice.
45mm is about perfect for a road racing setting, or someone wishing to go faster "most of the time" in comparison with all other profiles. They are light and climb very well too. Best all-rounder.
50mm is going to be a bit faster for a novice rider, wanting to get up a group in chaingangs etc. Average speeds can increase 2-3mph over box-section wheels. Good for bunch riding and fast stage racing for all levels.
60mm is the way to go for smooth rolling roads where outright speed is paramount. Ideal for TTs, Triathlon or Iron Man too. Noticeably faster than all shallower rims at speeds greater than say, 17mph.
Points we've noted from building these wider wheels and feedback from riders using them for a good few years now:
Choose a middle depth of 45mm or 50mm if you are just on the cusp of 17mph average.
If you aren't that fast (below 17mph average), a 38mm rim won't be much use to you aerodynamically. A 45mm might help, a 50mm or 60mm rim will definitely help.
Remember that tubular rims are lighter so can reduce the rolling mass of a deeper rim.
A stiffer carbon wheel slightly heavier than a shallow alloy set will climb considerably more efficiently due to the elimination of flex.
None of these wide rims are particularly affected by side wind loading. If reports of difficulties in crosswinds are worrying you, consider if it may be too windy to ride with any wheels safely.
We find a heavily bladed spoke design with a shallow rim such as Mavic Ksyrium SLR and Fulcrum Racing series can be more noticeably affected with side winds than a 38mm rim and Sapim CX-Rays
We'd only recommend a carbon tubular rim for specific climbing duties in the high mountains. No matter who the manufacturer is, a carbon clincher hook can deform at high braking temperatures.
Other than extra stiffness, a deeper section carbon clincher is pointless for climbing specifically. And when you rocket down 11 degree descents, they pick up so much speed, extra braking heat is inevitable.