Many people head to the high mountains in the summer. 3 hour climbs and 50mph+ descents are great fun. We have found over the years from listening to customers and going there ourselves that the best set of wheels to take would be a light set of maintainable, alloy-rimmed tubular wheels with some "race" tubs properly glued or taped on. This gives you a safe platform to climb and descend and if you do suffer a blow-out, the tyre sticks to the rim and you don't end up going down the mountain on an alloy rim edge.
Modern clinchers and tubeless setups with larger tyres and lower pressures can be just as puncture resistant but can blow off the rim if the worst happens.
Our new Aero38, 50 and 60mm rims have proven pretty much "unmeltable" in use on almost all the major climbs in the world - and even the 50mm sets are lighter than most alloy wheelsets that come "free" with new bikes. There will always be a first though....!
If you are used to shallow wheels, taking deep rims into the mountains and using them for the first time can catch you unawares. They pick up speed dramatically over 18mph and you will invariably be going downhill at that point, accelerating you faster than you are used to and ending up with you braking more - see braking tips below for issues concerning that!
But you don't have to go to the Alps to melt your carbon rims - there are demanding roads in the UK which need careful consideration too, especially for carbon clinchers. Avoid Bealach Mor and the Honister Pass with carbon clinchers for example. We have plenty experience of these roads and you are well warned! We have known riders to melt just about all brands of carbon rims on less demanding roads than these even. Therefore, we must assume it all comes down to technique.
Above all, dragging the brakes is a BAD technique with any vehicle - heat is the enemy.
Recently we saw an issue with a "Tektro direct mount" rear brake on a Boardman frame. These callipers are useless, as reviews will testify. But the feedback to the brake lever is so poor that even a damaged rim isn't felt through at the bars. Try to avoid a frame with these dreadful brakes.
Don't take carbon clinchers. Take a well maintained set of durable and stiff alloy wheels.
Don't take larger "Pavé" style tubulars or tyres, they aren't designed for the heat
Make sure EVERYTHING is adjusted properly, brake pads, bearings, gears etc
Have a good break at the top before descending, tiredness can kill
Do not position the pads near the lip of a carbon clincher rim. This could lead to deformation of the rim and possible overheating problems. It can also force the pads into contact with the tyre, again - very dangerous.
Use the pads supplied with the rims. Blue Cryo for Wheelsmith carbon rims and ENVE for ENVE rims - grey for standard rims, black for the new textured rims. SwissStop pads are not recommended as they melt at too low a temperature and leave unpredictable streaks on the rim.
Don't assume that because you have been riding for years it makes you an "expert" when it comes to braking technique. Carbon rims require a different approach.
Whichever type of wheel you take, you do so at your own risk. A blow-out from an overheated clincher can be disastrous. An aluminium rim heats up faster than a carbon rim, but it will cool faster. Inner tube pressure builds up with the heat and can blow tyres off the rim, or can even crack a worn alloy clincher rim braking surface. You will notice on the Etape du Tour, Fred Whitton, Dragon Ride etc, that blow-outs are commonplace - these are usually due to over-pressure and over-braking or both. An overheated rock-hard tyre can skip over a uneven surface and the constant impact can pop the tube.
Tips for successful braking:
Don't "drag" your brakes - front or rear. This goes against most riders' natural reaction but it is an unsafe technique, unless you are faced with icy or greasy roads when you are going slower and need ultimate feedback from the pads
The correct technique is to brake late and for as short a period as possible
Release the brakes while the bike is moving and the rim will immediately begin cooling
Learn and practice the technique and you'll be able to stop sooner and avoid overheating rims
Front brake first, gradually increasing the force over a second, but no more
Reapply if necessary
Don't "skid" the rear, you will lose direction and it is pointless and dangerous
If you are over 90kg, manage the risk by considering a disc brake setup if you must ride carbon clinchers.
Overall, there are no wheels we currently offer here that can't be used in the Alps etc with correct technique and care. Heat dissipation can be easily controlled with careful and correct use. We can repair everything here except you - respect your equipment and your own mortality.
From experience, the problems we see are usually from the "I know what I'm doing, I've been braking for years" guys.
Generally speaking, it's the "I don't brake much" customers who never have any issues and take their carbon wheels around the world in relative safety.