Bicycle Mechanics - Drum brake question
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07-16-07, 09:59 PM
I would like to put a drum brake on an old bike I'm building. my first thought was to use a tandem hub, but I don't want to respace the frame to 140mm, and I am going to run it singlespeed anyway. I did some searching, and the drum brake is threaded 1.375"x24 pitch, the same as a freewheel. My thought now is I just need a flip flop hub, I should be able to thread a freewheel on one side and the brake on the other. Has anyone else tried this, I would like to know before I start buying parts.
07-17-07, 07:51 PM
It may go together the way you want but check drum brake clearances at chainstay and seatstay. If you are aiming to use an Arai drum brake, it is designed to be a drag brake for a tandem - it doesn't stop very well and is heavy.
07-18-07, 08:44 AM
The Arai drum brake is not made for quick stops, emergency-style; however, it still compares fairly well to whatever braking you can get from the rear brake. In other words, if you grab the lever very hard, you can skid the rear wheel. It needs to pull a fair amount of cable, therefore it works better with a v-brake lever than with a canti-brake lever. I would NOT recommend having the Arai drum brake as your sole brake (it's a bit like having an oiled coaster brake), but it would work great in conjunction with a rim canti- or v-brake on the front wheel.
Still, the great advantage of the Arai brake is that it's almost impossible to overheat it. So that's a great safety policy for those multi-kilometer long downhills.
Coming back to the original poster request:
1. In theory, you could use a flip flop hub. However, you'll need to buy a 120-mm hub with a 135-mm axle (or something like that, I don,t know the precise measurements) to install a freewheel on one side and a drum brake on the other. It would work, but you would have the worst of both worlds:
– a freewheel, limiting you to 7, or at most 8 speeds, which means little or no availability of indexed shifting;
– an unsupported axle on both sides, meaning more possibility of axle breaking.
2. If you look carefully around, you could get a 135-mm tandem hub, or even a 140-mm tandem hub respaced to 135 mm. In both cases, it means a freehub and the latest technology. Bear in mind that tandem hubs are NOT cheap, except for the Shimano tandem freehub, which is available only in 140 and 145-mm width.
3. "Old bike" most certainly means steel (check with a magnet), in which case you can spread it. I would not spread from 120 mm to 140 or 145 mm, but spreading from 126 to 135 mm can most certainly be done. And spreading to 135 mm makes sense in that you can put any standard "touring" wheel (or spread to 130 mm to install any standard "road" wheel).
The OP wants to run single speed, not multiple freewheel.
07-18-07, 10:46 AM
With the Arai drum brakes, clearance may be a problem, and they are heavy.
BUT they can be a very effective stopping, as opposed to drag, brake if they are properly set up.
So maybe you already have the Arai and you're trying to figure out how to use it. If you're starting from scratch I'm wondering what is the motivation for drum brake-age. I have toyed a bit with Atom rear hubs and front hubs for tandems and a bit with Shimano drum-like brake attachments that mesh onto the non-drive side of their nexus internal hubs and nexave hubs. Are any of those possible candidates?
Sturmey archer makes a drum brake for single speed, the XRD.
Otherwise, you can do the 3 speed rear drum brake hub in the same dropout spacing, the Sturmey XRD3.
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