We have disc brakes on our mountain tandem. I have to say I totally disagree with Robin Thorn about this. His information is way out of date. Ours are hope M4 front on a 203mm disc ( soon to be replaced with a 6Ti) and a 6Ti rear with a 185mm disc. Using a marzocchi Z150 lite fork with a reinforced steel steerer and 20 mm axle.
We have ridden this bike for 4 yrs - on road and off, fully loaded touring thru the highlands and down downhill mtb routes . We have hit nearly 60 mph on downhills What you mustn't do is drag the brakes ( or if you must drag alternate them)- but you have such reserves of power there is no need. Instead you use them like a motorcycle or car - braking to slow when needed otherwise tuck in and go! We have cooked them twice - both times dragging one brake slowly down a long descent. Both time the brake gave warning it was going to overheat by a change in lever feel giving plenty of time to slow to a safe halt. I have never heard of anyone having a disc warp and jam. I can only assume if this happens that they did not have the correct equipment fitted. (perhaps small rotors??) Hope will happily spec their brakes for tandem use.
Hope now do disc brakes with ventilated rotors for extreme use.
Myself having use the power of the discs and being used to them I would never want to rely on a rim brake again.
A couple of things Robin thorn is wrong on. In his information he says "..........we could have lived with through axles but the blades would also have needed to be un-tapered blades 31.8mm in diameter... we know how uncomfortable un-tapered 25.4mm blades..........." Whilst I agree with him about the 20 mm axle (altho by careful dropout placement the risk of wheel ejection can be avoided) both cannondale and dawes supply tandems with discs and tapered curved QR forks. He also states "........no manufacturer makes a fork specifically for tandem use, so there is nothing available which has the correct geometry, let alone a warranty for tandem use." This is again wrong - whilst tandem rated forks are not common they are available - Marzocchi do some and so do other manufacturers and are happy to guarentee them for tandem use. Some require modifications such as fitting reinforced steel steerers. Geometry is simply not an issue in my experience and that of many others who use suspension forks. An american company will supply fully built tandems with guaranteed suspension forks.
Also in the Thorn tandem catalogue it says "100kph can easily be reached, when descending Crowcombe without braking, on a tandem... the standard V brakes will stop the machine (on the 1 in 4 section) within 100m" That simply is not good enough. 25m with discs as an estimate even allowing for the fact you are still on a steep slope{ I would expect under 20 m from 100kph on the flat) ( highway code states 18m for a car and that in itself is outdated) we can brake hard enough to have a 2.3 inch sticky tyre squealing and slithering and the rear totally unweighted. we can stop quicker than many a car from 100kph
I am afraid Robin is simply years behind the times here. Technology has moved on and the things he questions simply are not an issue. He is condemning his riders to use inadequate rim brakes with all the problems they have rather than proven effective discs. No more rim wear, no more poor wet weather braking. easy instant 1 finger stopping
