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Thread: Braking Systems

  1. #1
    El Diablo 2Rodies's Avatar
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    Braking Systems

    We just bought an early 90's Burley Duet. This being our first tandem and having spent all of my time on singles the first thing I noticed was how "spongey" the rear brakes felt. Is this normal due to the long leangth of the cable. The rear brakes are Avid (long throw not the shorties). Would the Avid shorties increase or decrease this feeling? If this is not normal any recommendations would be welcome.


    Thanks in advance,

  2. #2
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by 2Rodies
    We just bought an early 90's Burley Duet. This being our first tandem and having spent all of my time on singles the first thing I noticed was how "spongey" the rear brakes felt. Is this normal due to the long leangth of the cable. The rear brakes are Avid (long throw not the shorties). Would the Avid shorties increase or decrease this feeling? If this is not normal any recommendations would be welcome.


    Thanks in advance,
    Early 90's would make the brakes old style cantys. The "feel" of old style cantys is greatly affected by the shape of the triangle formed by the straddle cable. A long narrow triangle will have a much "firmer" feel than a short wide one.

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    El Diablo 2Rodies's Avatar
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    The rears have been upgraded to an Avid brake, the fronts are still the canty's. I was curious about the spongy feeling if it is normal because of the cable lenghth. The Avids on the rear are the long throw and I thought maybe the Avid shorties would decrease the spongy feeling.

  4. #4
    Senior Member Retro Grouch's Avatar
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    Quote Originally Posted by 2Rodies
    The rears have been upgraded to an Avid brake, the fronts are still the canty's. I was curious about the spongy feeling if it is normal because of the cable lenghth. The Avids on the rear are the long throw and I thought maybe the Avid shorties would decrease the spongy feeling.
    I've never noticed "spongyness" that I attributed just to the longer brake cable. Can you post a photo of what your set up looks like?

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    SDS
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    Retrogrouch is exactly right. You should embark on a brake setup optimizing campaign, starting by running out the straddle cable to a tall triangle with just a small margin before hardware starts running into the brake cable housing stop at full application. You need to true the wheel and take the shoe/rim clearance down to the minimum. And you have to remove any mush from the front end of the system. If you see the rear brake cable housing move when you apply the rear brake, that will use up some travel. You can prevent this by ziptying the rear brake cable housing to the front brake cable housing where they cross, which will deny it the opportunity to flex. When you are done you just might be able to lock up the rear wheel with a stoker on board.

    Lots of tandems out at Peach Pedal today (Weatherford, TX), including Art Cowsen (everybody's hero, you can see a picture of our Fearless Leader on the FWBA Death Ride picture pages) on his extended stoker compartment CoMotion Capuccino and Duane Neu on a triple with his wife and hapless son. I'm old, lazy, and fat, so I could only manage 2:48 for 62 miles on my single. I might have seen two tandems towing trail-a-bikes towing trailers. Mind-boggling. Watching those things turn U-turns across the better part of four lanes is amazing.

  6. #6
    Senior Member zonatandem's Avatar
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    Howdy from Duluth!

    Another option is to add a brake stiffener/booster, available in alloy or even carbon fiber.

    Pedal on TWOgether!
    Rudy & Kay/Zona tandem

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    hors category TandemGeek's Avatar
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    Quote Originally Posted by 2Rodies
    Is this normal due to the long leangth of the cable.
    Yes, this is a normal and accurate first impression. You have twice as much cable and at least twice as much cable stretch.

    (Or -- with a nod to Scott -- to be more accurate, you end up with at least twice as much loss of efficiency in the "system". More specifically, on a single bike you lose cable-pull efficiency by a factor of X due to various things. On a tandem, the factor is ~2x. At the same time, you are exacerbating 2x because you are riding a bicycle that weighs twice as much and are pulling on the brake lever 2x as hard in an effort to achieve the same result. When you combine all of those things, you end up with a rear brake that feels "mushy" and would feel mushy even compared to the same brake device on a single bike.)


    Quote Originally Posted by 2Rodies
    Would the Avid shorties increase or decrease this feeling?
    As Retro noted, I'd probably need to see a photo of your current brake set-up before making any specific recommendations on how or what to tweak to achieve what result. As you can see from some of the other responses, there are quite a few different ways to "firm up" a canti or linear pull brake, some are merely adjustments to reduce cable travel along the run or at the brake, others involve fitting different brake pads to improve the "bite", brake "boosters" to neutralize flexing at the seat stays or forks, or different models of brakes that may or may not have more inherent flex. However, underlying all of this needs to be cost-effectiveness. After all, once you have enough brake leverage to lock the rear wheel, you have "enough". Any more than that might give you some marginal improvement in brake lever "feel" but it won't make your tandem stop any more efficiently as that remains the domain of the front brake.

    Just my .02.
    Last edited by livngood; 07-11-04 at 07:32 AM.

  8. #8
    El Diablo 2Rodies's Avatar
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    So I had the chance to check out another "older" tandem today and the rear brake felt just like ours. It is the cable length and I'm just used to the feel of a single. Thanks for all of the responses we are going for our first (as a team) ride this evening!

  9. #9
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    Sometimes a bend in the cable routing contributes more to sluggish feel than length of the cable. My step-through single has a less crisp feel than our Raleigh companion's rear brake ... but the tandem cable is a very straight route and the step thru has a nice cable bend up to the brake. At least this is what my mechanic convinced me of on the step thru -- essentially there is alot of friction, the cable in the casing doing the bend.

    jus' another tho't

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