Brian

Ok, I just read about Ricardo the mad Colombian (nice work!) and it got me thinking about drag brakes. We don't need, nor can we mount a drum brake. I'm liking the idea of a single canti on the back, operated by a thumbie on the stoker's bars. Just enough for my wife to control our speed on short but steep downhills. Installation should be easy enough, but how effective will this be in keeping speeds down so she feels comfortable?

MisterJ

The problem with rim based brakes as drags for speed control is overheating. Hot rim=tire failure.

Mr_Super_Socks

There's nothing inherently wrong with having the stoker control a drag brake, but for a variety of control reasons, it makes more sense to have the captain control the drag brake. good communication from her to you, and good responsiveness by you would be just as effective and safer. the point about overheating is important, too. have you considered replacing the front wheel with a disc-brake compatible hub. this should be a workable (though not cheap) option.

Brian

We've got XT 203mm discs front and rear already. Her complaint is that she has no controls on her bars, other than a bell to ring (and a GPS and HRM to look at). I don't think our heavy duty Rhyno Lites will heat up quickly on short steep sections. We're just looking for a bit of friction to slow us down, at her discretion.

Steve Katzman

We thought about giving the control of the drag brake to the stoker but we didn't because of the hypothetical situation where a car is approaching on a cross street. I (the captain) feel if we gun it, we can cross the intersection before the car arrives. The stoker calculates differently, panics, and applies the drag brake and puts us squarely in no mans land. Hmmm, does this constitute an exception to the "stoker makes no mistakes" rule? We felt it safer for the brake control to be the responsibility of the captain.

TandemGeek

Nope. The mistake in that situation would have been that the stoker wasn't properly instructed on when it was permissible to use the drag brake and communicating the intention to do so.

Seriously, one of the key tenets of giving the stoker controls -- as well as taking them away such as when you first start riding tandems -- is discussing the rules of engagement and commands BEFORE you ride and then communicating your actions AS you ride.

A drag brake has two uses:

1. Controlling downhill speed
2. A nifty parking brake

Under no circumstances should a stoker apply the drag brake or use any other auxiliary brake control (and even then the use should be accompanied by a lot of discussion) until such time as a team has been riding and using the drag brake long enough to intuitively know when it should be used and to what extent. After all, if you're bombing down a hill and approach a curve, the last thing you need to have happen if you haven't called out for the drag brake's use BEFORE you begin to brake with your rear brake lever or AFTER you've applied it would be the stoker's use of the brake which could, given the right conditions, lock up and/or skid the rear wheel out from under the back of the tandem with the expected and nasty consequences that follow.

TandemGeek

The proposed cheap drag brake would, IMHO, work just fine. I say this first and foremost based upon your experience, your equipment, and other things that you have shared with the list.

As for rear tire blow-offs from overheating, we could be the exception to the rule, but having melted a pair of Shimano XTR V-brake rear brake blocks on a nasty, 1 mile long nasty forest service road descent whilst running Sun Rhynolite 26"ers with IRC Mythos XCs inflated to 45psi, I would have to say that there is a lot of heat capacity in off-road tires and wheels. Thus, for the proposed application -- off road auxilliary speed control -- I suspect there is not a whole lot of risk and it would be limited to the rear tire.

Were the conditions and equipment altered such that you were running higher pressure slicks and using the rim brakes for on-road touring, I suspect there would be a higher potential for a rear tire blow-off.

Mr_Super_Socks

If this is about needing a feeling of control, you might be better served to work on communication. It sounds like you are going at a speed that she feels uncomfortable with. As a rule, the captain must slow the bike when the stoker wants you to. if the reason she wants a brake is to slow you both down when you are otherwise unwilling to, that poses a serious hazard. One scenario has been painted, but there are countless others. Don't just give her control of a drag brake - give her control of the whole bike and SLOW DOWN when she asks you to.

Brian

She trusts me to go as fast as I want, but I think she would prefer not to go as fast as I go. Does that make sense?

Next problem: I'll have to locate and re-install the brake posts, but if I recall correctly, canti's require something extra in the way of a cable stop. Suggestions?

Brian

So am I going to have to fabricate a cable hanger that attaches to/near the stoker's seatpost clamp area?

TandemGeek

Two choices, if you plan to use a cantilever you can buy a cable hanger that mounts to your stoker's seat post clamp bolt. If you use a linear pull brake like a Shimano XT V-brake or an Avid Single Digit the 'noodle' provides that function. The larger issue is finding / fabricating bolt-on cable stops otherwise you'll have to run cable housing all the way from her brake lever to the rear cable hanger.

Brian

I guess I should just use a V brake then. For some reason, I was under the impression the Avid canti's were the way to go for a tandem. The bonus to having a custom frame is that extra set of cable stops.