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Recumbent What IS that thing?! Recumbents may be odd looking, but they have many advantages over a "wedgie" bicycle. Discuss the in's and out's recumbent lifestyle in the recumbent forum.

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Old 10-11-06, 03:23 AM   #1
redbug
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Disc brake questions

I could do with some advice about disc brakes, it's not for a recumbent, but it's a situation that a lot of recumbent trike builders/riders must come across. Also can i confess that i know nothing about disc brakes, i've not got a bike with them on and i've not even ridden a disc braked bike.

Having said that i am building a load carrying trike, you know the sort with two wheels at the front and a box between them. A bit like this: www.christianiabikes.com/english/uk_main.htm and i am going to fabricate the mounts and fit mechanical disc brakes to it. As it's going to have quite a long wheelbase, and the danger of flipping forward will be minimal, i'm going to use a canti brake on the rear as a parking brake and the discs on the front wheels as the main system. The question is, as i am using two front wheels, do i need two front disc setups?, or can i buy a regular front/rear pair and use those?

I'm hoping to mount the front wheels with the discs 'inboard', as it were, so as to give some protection to the rotors. What is the difference between a front setup and a rear anyway? Is it just the mounting holes for the calipers are in a slightly different place, or are the discs or calipers fundamentally different? Help!
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Old 10-11-06, 06:39 AM   #2
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You will need a front-wheel disc brake for each of the front wheels. You probably won't need a brake for the rear at all, as the dual disc brakes will probably have enough stopping power. A rear brake may also cause the rear end to skid and fishtail in some stopping conditions. At most, you can use a rear brake as a parking brake, but not for routine stopping.
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Old 10-11-06, 12:36 PM   #3
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Originally Posted by jeff-o
You will need a front-wheel disc brake for each of the front wheels. You probably won't need a brake for the rear at all, as the dual disc brakes will probably have enough stopping power. A rear brake may also cause the rear end to skid and fishtail in some stopping conditions. At most, you can use a rear brake as a parking brake, but not for routine stopping.
Thanks, thats what i thought really, but it's good to know that someone who knows what they are talking about, thinks the same. I might connect the rear brake to a gear shifter on a seat stay, to use as a parking brake. The hugely long cable run from the handlebars makes it impractical for normal braking anyway.
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Old 10-11-06, 02:06 PM   #4
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One other thing, you can actually get brake levers with a "parking brake" feature. I think Tektro makes some. They have a little button that you can press once the brake is engaged, that holds the brake lever down.
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Old 10-12-06, 02:42 AM   #5
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Originally Posted by jeff-o
One other thing, you can actually get brake levers with a "parking brake" feature. I think Tektro makes some. They have a little button that you can press once the brake is engaged, that holds the brake lever down.
Yeah, I've seen something similar but i think i'll try the shifter idea first as it's less bulky for the seat stay, and a 'zero cost' option. Cheers.
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Old 10-12-06, 08:07 PM   #6
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The rear brake is also used as a 'drag' brake for long or fast downhills. Trice provides this option. They too use a frame mounted shifter lever for setting this brake. It sounds like you plan on carrying payloads and if hills are in the territory, a drag brake may be a good safeguard.
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Old 10-13-06, 05:50 AM   #7
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For a drag brake on hills, I would think you'd want a drum brake that won't be susceptible to overheating the way rim brakes are.
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Old 10-13-06, 12:30 PM   #8
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The rear brake is also used as a 'drag' brake for long or fast downhills. Trice provides this option. They too use a frame mounted shifter lever for setting this brake. It sounds like you plan on carrying payloads and if hills are in the territory, a drag brake may be a good safeguard.

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For a drag brake on hills, I would think you'd want a drum brake that won't be susceptible to overheating the way rim brakes are.
I could use it as a drag brake, thats a good idea. The trike's principal function will be kid transport so the associated safety issues and the fact that 'long or fast downhills' always require looooooooooong slow uphills first will mean that the drag brake won't get used too much. Although I am hoping to take it touring next year, to the Netherlands, where a bridge over a motorway counts as a substantial incline.
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Old 10-27-06, 08:29 PM   #9
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The trike's principal function will be kid transport
What out for the pirates!
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Old 10-28-06, 07:49 AM   #10
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Woha!
Originally Posted by Shaman
"The rear brake is also used as a 'drag' brake for long or fast downhills. Trice provides this option. They too use a frame mounted shifter lever for setting this brake. It sounds like you plan on carrying payloads and if hills are in the territory, a drag brake may be a good safeguard."

Originally Posted by BlazingPedals
"For a drag brake on hills, I would think you'd want a drum brake that won't be susceptible to overheating the way rim brakes are."

Your both right, but rim and disk brakes should be avoided for use as a drag brake on any loaded bicycle. Both will over heat when used as a drag brake. The rim brake can over heat the rim causing the tire to fail, the disk brake will also over heat warping the rotor and eating up the pads. For a drag brake use a Aria drum brake mounted to a tandem hub. For more information see http://www.precisiontandems.com/arai.htm

The bike in the pirates is set up with drum brakes (Great photo Rodger!) The brakes have been modified to use stub axles, just like many recumbent trikes that use drum brakes.

The christiania "light" weighs in around 77 pounds, then add the rider 160 pounds, and the two kids at 50 pounds. 337 pounds... Can two disk brakes bring this mass to a quick safe stop? Yes, I've tested them in the real world (Organic Engines Tandem trike, two adult riders and 80 pounds of camping gear) About 530 pounds from 32 mph during a down hill run on tour in VT. And you can be sure I caught hell from the stoker for that test!

As for your disk brake question. Get the largest rotor available for the brake your going to use, Avid offers 203mm rotors for their mechanical disk brake. The larger the rotor the better it can dissipate heat. And you will want to protect little fingers from touching the rotors as they do get hot (300+) when used for heavy loads.
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Last edited by bentbaggerlen; 10-28-06 at 07:59 AM.
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