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Overheating rim brakes -> discs?

Robert Jamison2021-11-09 11:50:32

We tandemed down to Gibraltar and the Spanish mountains are just that - mountains. On descending the first pass the rim V-brakes overheated, melted the plastic rim tape, thus exposing the spoke holes, which caused the tube to explode and the tyre wall to shred for a 4" section, exposing the wires, and we hit the deck. Thankfully we had been slowing up to take a right turn, so impact speed was 20-25kph and we limit ourselves to 40kph. 80km ambulance ride to hospital ensued for a brain scan and help with unpleasant facial cuts and bruises. Thankfully nothing broken or serious. All healed after a week.

We were riding an Ecosmo folding tandem with 20" wheels, Schwalbe (Road Cruiser) tyres and tubes, with 2 panniers and a Burley luggage trailer in tow. All up about 190kg. The brakes had been fairly full on for 2.2km and an average gradient of 1 in 10 according to the map.

Disc brakes then come up for discussion to avoid this problem and unhappy experience. Does anyone know of when disc brakes fail, perhaps through similar over-heating or some other issue?

Perhaps the more familiar (to me) and possibly more robust rubber rim tapes are the simple answer?

David Ebling2021-11-09 20:34:43

Ouch! Sorry to hear of your crash.surprise

Smaller wheels will be more prone to overheating than larger ones as they have less mass to spread the heat through, have less surface area for cooling.

Farbic rim tapes would be a more resilient choice I think, although I couldn't guarantee that the glue wouldn't soften with extreme heat, and the tyre could still burst from heat directly.

Discs probably won't get any less hot but wont cause tyre failure.  However the pads can glaze at high temperatures and hydraulic fluid can boil causing failure. If you go down that route, get the biggest disc size that you can fit.

Traditionally people use Arai drum brakes on the rear wheel of tandems for long descents, but they are hard to find now.

I would consider fitting both disc and rim brakes if you are descending a lot, as if the discs fail you can being yourself to a stop with the rims brakes. How you control them isn't obvious though. Giving stoker brake control isn't a popular setup, but if it's for emergency use only, perhaps that could work.