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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 06-24-12, 01:22 PM   #1
Tandem Tom
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Disc Brake Questions

Still a newbie here but wanting to learn more about the disc brakes on our Co-Motion Speedster.
While riding today the thought crossed my mind, "How do you know when to replace the rotors?"
And in the Tandem@Hobbes email, which I cannot figure out how to post to, the discussion was about rear discs. They made mention of "travel multiplier and travel agents? What are these items?
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Old 06-24-12, 01:40 PM   #2
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The travel multiplier / agent is a in-line adapter which (through the use of leaver & fulcrum) boosts your breaking power. you don't really need one with full disk all around.
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Old 06-24-12, 02:01 PM   #3
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Originally Posted by Tandem Tom View Post
While riding today the thought crossed my mind, "How do you know when to replace the rotors?"
The Avid rotors start out around 1.85mm in thickness. While Avid's documentation is moot on the point, general rule of thumb is the loss of about .2mm - .3mm and/or a thickness of not less than 1.5mm for the rotor. For the brake pads, they should be replaced when the overall thickness of either pad + backing is less than 3mm.

Originally Posted by Tandem Tom View Post
They made mention of "travel multiplier and travel agents? What are these items?
This is a photo of a tandem with a "Problem Solver Travel Agent" installed. As noted, it's a device the modifies the mechanical pull of a brake lever. V-brakes were not designed to work with integrated road shifter/brake levers and early on the desire to use V-brakes on tandems caused folks to develop these things for people who mixed and matched incompatible brake components. Newer integrated brake/shift lever from Shimano how have sufficient mechanical pull to mitigate the need for these adapters.

You can find all kinds of information in the BikeForums archives using a Google search string, including "travel agents". Just use a search string that starts with " " and then add your search terms. For travel agents I'd use something like " tandems travel agent brakes".

This post is an example of what you'll find:

Hobbes is a Listserver, which means you need to subscribe via Email. All postings are made / received via Email. More information at my Website or the Hobbes information pages. Just Google on "Tandem@Hobbes subscribe" or words to that affect.
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Old 06-24-12, 08:31 PM   #4
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TG, your info on pad replacement thickness is text book.

From experience, (several times to admit being stupid), the disc pads will not wear to the Avid stated minimum thickness and still stop. At about .1mm above minimum thickness, maybe slightly less than .1mm, the spring clip, which also is a squeal device, will become your friction surface.

The bike will not stop when this spring clip is used as a brake pad. Jeanne got a wild ride as we totally blew an off camber turn on the Fandango MTB tandem, while training earlier this year. Suffice to say she was pretty irked about us going 15 or so feet off the trail before I got the bike turned back up the hill. A two minute team meeting about why we had to end our ride early did not settle well either.

In summary, if you have brake pad rub that seems to never subside, regardless of how well you adjust the pads, you might want to measure and / or replace the pads. The noise you hear is the spring clip tips "talking" to you.

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