Not to inflame an already heated discussion. It would be good for people to reference more authoritative work. For example Wilson's Bicycling Science is a great source. Here are figures for (1) rim temperature increase during constant braking versus speed and (2) terminal velocity versus %slope. From these graph 1 you see for constant braking to maintain 40 MPH, a single bike does not heat rims more than 50C even on a 20% slope. My concern would be temperature increases closer to 100C (melting temperature of butyl rubber, 120C). I have been concerned of late with this on a tandem since we often bike in mountains. For a tandem, >10% slope can cause temperature increases that are much higher. Wilson does not mention pulsing brakes. I have heard anecdotal talk that pulsing does allow air flow between pad and rim/disc to prevent brake pad melting.
