All Carbon Wheels have temperature restrictions.
Typically this is in the range of 170C - 200C
Above the rated temperature - the carbon becomes soft and can deform suddenly.
Clincher Rims are more sensitive because the tire pressure may 'warp' the rim when it overheats.
GS Astuto's rims are constructed with high temperature resin. (190C) and also use a special Basalt fabric on the braking strip to help resist damage.
In addition, the special brake pads help to lower the braking temperature by 'shedding' or 'dusting' under heavy braking. So, you must ALWAYS use Carbon Rim Brake Pads!
While we do our best to make the safest and toughest rim possible, it is important to know that overheating CAN HAPPEN - especially under HOT, STEEP and SLOW descents.
1) Make sure brake pads are mounted properly. Generally 2mm from the top edge of the rim.
2) Use BOTH BRAKES when slowing down or stopping.
3) Avoid continuous 'feathering' of brakes while descending.
4) If you feel pulsation when you are braking, then immediately stop and check your rims.
5) On very long, steep, descents you may need to stop periodically and let your rims cool down.
via GS Astuto.