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to disc or not to disc that is the question..(3 posts)

to disc or not to disc that is the question..cyclopathic
Mar 6, 2003 9:14 AM
to tandem owners
It depends (long, longer, longest?)TWD
Mar 6, 2003 11:31 AM
Brace yourself, I've done a lot of thinking on this subject. Here goes a rather lengthy answer.

On our road tandem we have used cantis, Vs, and Magura HS-66 Hydraulic Cantis in addition to running an Arai Drum Brake as a drag brake. I haven't used discs on our tandem as we're not set up for them and it wouldn't be worth it to try to retrofit.

I do run Avid mechanical discs on my mountain bike though and love them, especially in the wet conditions that I ride in regularly.

The Avid road discs are the only road lever compatible discs that I'm aware of and they are very similar in design to the MTB version.

Judging solely on my experience with the Avids on my MTB, and various rim brakes on our tandem, I think the Avid road discs would have a good bit more power than a canti or V brake and probably comparable power to the HS-66s in dry conditions. The discs will be far better than any rim brake in the wet.

The Avids come with 160mm rotors which would be plenty for a single (and probalby overkill) but I'm not sure they would be big enough for tandem use depending on if you ride in the mountains, are a heavier team, or do loaded touring.

I don't think the issue is necessarily stopping power, but more heat dissipation when you're controlling your speed on long/steep descents. On my mountain bike, the Avids will start to loose some stopping power and begin to squeal if you drag the brakes for long periods of time (10 to 15% grades for several miles for example). The heat generated is tremendous (enough to leave a big scar on my calf from brushing the rotor). The amount of heat you'll generate on a tandem would be far greater.

One option would be to get the Avid MTB discs which have optional rotor sizes up to 203mm, which would give you a bit more stopping power and handle the heat better. Since they are MTB brakes, they are set up for levers that pull the same amount of cable as a V brake lever, so you couldn't use them with standard road lever. You would have to get DiaCompe 287-V levers (i.e no ergopower or STI here) and use barcons. The road and MTB versions of the brake both have adapters to run the International standard disc mounts, so I assume they would work (I'd double check with Avid, your LBS, and/or the frame manufacturer to be sure).

Two more considerations to this lengthy dissertaion would be warranty issues and adjustability.

In terms of warranty, you'd have to check with Avid to see if they rate their road discs for tandem use. I doubt they do, and if not, using them would void your warranty.

In regard to adjustability, Avids MTB mechanical discs are great in the fact that you can use a MTB lever with adjustable leverage ratios (Avids Speed Dial levers) to adjust the feel of the brake. You can set them up to be grabby or "detune" them a bit for a more controlled/modulated feel. You won't be able to do this with any type of road levers. You'll be stuck with whatever feel that they have with your current lever, like it or not.

Since we do alot of tandeming in the mountains, I think I would stick with the HS-66s and drum brake. That said, I know of a least two tandem teams in the area (Oregon) that are running the Avid Discs and as far as I know they are happy with them. Both are lighter teams, and are more race oreinted.

If we lived in flatter terrain or were a lighter team, I think they would be great.

Hope this helps with your decision.
thanx, good infocyclopathic
Mar 6, 2003 2:14 PM
I'll go with V-front mech disc rear; prob run some wimpy disc like Deore with road levers.