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  1. #1
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    disc brakes on tandem

    Hi, Comotion does not recommend using front and rear Avid disc brakes when doing loaded tours with steep down hills , is this possible , they rcommend a drum brake and cantilevers. since i had no problem on my santana with the winzip( 10 in) and dura ace up front ,I,m wondering why two 8 in avids wont do the job ?

    thanks André

  2. #2
    Senior Member Homeyba's Avatar
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    Probably because the forces generated by the dick brakes of a fully loaded touring bike are beyond the design parameters of the Comotion. Especially on the front fork. It'd be a major liability issue for Comotion if someone crashed on a fast descent because the front brake caused the fork to collapse. It's cheaper to just say no.

  3. #3
    hors category TandemGeek's Avatar
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    Quote Originally Posted by andre marcoux View Post
    Hi, Comotion does not recommend using front and rear Avid disc brakes when doing loaded tours with steep down hills, is this possible, they recommend a drum brake and cantilevers. since i had no problem on my santana with the winzip( 10 in) and dura ace up front , I,m wondering why two 8 in avids wont do the job ?
    Based on following this issue for over a decade, personal experience and discussions with the folks in the industry three reasons seem to rise to the top:

    1. For loaded touring or any other heavy-duty requirements where constant braking would be required on a long, steep or long-steep descent, Co-Motion's recommended set-up has been proven over time to be the most effective. The reason for this is straight forward: the Arai drum is an application specific supplemental 'drag-brake' designed to deal with very high heat loads and that works in parallel on a non-interference basis with rim brakes. Note: At present, no one has designed a disc rotor with an integral drum brake so the use of one precludes the use of the other.

    2. When Co-Motion first began to offer the Avid discs as an option Avid was still a small Colorado-based company who had a good relationship with the folks over at daVinci Designs / Tandems. The folks at daVinci did a lot of beta testing with Avid's 203mm mechanical disc brakes at a time when there weren't any road tandem-rated / approved disc brakes on the market except for a klugged-together and problematic mechanically-actuated, hydraulic Formula rear disc by Santana. Based on real-world results by the folks at daVinci -- to include doing the epic Mt. Ventoux and Alps du hez on an Avid BB7 equipped daVinci tandem -- Avid agreed to characterize their discs as suitable for use on tandems as a primary brake so long as only the 203mm model was used. Looked at another way, while the Avid lacked the overall heat capacity of an Arai drum brake, it was still as good as or better than rim brakes. This allowed Cannondale to sell their RT models with dual discs and Co-Motion also offered up the Avid's as rear and/or front & rear primary brakes in place of rim brakes which are probably more than adequate for 90% of all tandem teams. However, for anyone who truly required a drag brake, see #1 above. If fact, early on if someone wanted rim brake mounts and a disc brake mount Co-Motion made a point of providing only one set of brake cable stops too preclude the use of the disc as a supplemental drag brake. Obviously, any resourceful consumer could easily modify their Co-Motion to accommodate a second brake cable installation to thwart Co-Motion's efforts to abide by Avid's guidance, but at that point it was on the owner not Co-Motion if they go into trouble.

    3. With few exceptions, if a couple buying a tandem is candid about how they'll use their tandem any one of the standard brake packages will usually be more than adequate to meet their needs. True tourists know who they are and will eschew the trendy discs or racing brakes and gladly use the rim + drums on their tandems along with mud guards and racks and the same usually holds true for folks who ride multi-seat tandems (triples, quads, etc). Racers and go-fast riders will use the same brake package they have on their single bikes, e.g., dual rim brakes and calipers where possible. For racers and faster recreational riders who venture into mountains with technical descents, a rear disc offers a belt and suspenders approach that gives them added brake-heat capacity to deal with the unexpected (yikes, I didn't realize how gnarly this was) or that special descent on a certain ride they do where something better than a rim brake is called for, but a drum brake would be overkill. All of the other 'options' are simply variations that may or may not be any better than the 3 basic configurations. In fact, there are even folks who have rear discs as a primary brake running around with a stoker-controlled rim brake.

    So, as a consumer you're free to buy from the slate of options that Co-Motion and anyone else offers. If you've been successful using a front caliper and rear disc on what you consider to be loaded touring and on terrain that represents the upper end of what you will seek out in the future, then you could probably assume that a similar configuration on a Co-Motion would work just as well (WinZip 10" isn't all that more robust than Avid 8", despite the marketing spin) or even dual discs. However, that's a personal choice that you're free to make. Co-Motion, on the other hand, must apply a level of conservatism as an OEM and that's what forms the basis for their recommendations.
    Last edited by TandemGeek; 07-28-09 at 01:07 PM.

  4. #4
    Hill Riding Team
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    As has been said before on this post and others - it's horses for courses.

    This couple looked to have had a favourable experience with their tandem using Hope hydraulic brakes and Rohloff gears:

    http://www.karennben.com/

    We ride with 2 disks and a V-brake as a spare. The V-brake is very much the third choice. Our trips are generally hilly (English Peak District, Col du Tourmalet) but not usually heavily loaded. The reason for going for 2 disks (front is Avid BB7 8" rotor) was better stopping power and we wore through our first set of rims in <2000 miles.

    Maintainanbility and access to spares might also be a consideration depending on the destination.

  5. #5
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    thanks , I sold my Santana team al( remember I had trouble with the shimmy) , and I will buy a comotion ,with the disc brakes ,and see for myself what happens .
    andré m.

  6. #6
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    "So, as a consumer you're free to buy from the slate of options that Co-Motion and anyone else offers. If you've been successful using a front caliper and rear disc on what you consider to be loaded touring and on terrain that represents the upper end of what you will seek out in the future, then you could probably assume that a similar configuration on a Co-Motion would work just as well (WinZip 10" isn't all that more robust than Avid 8", despite the marketing spin) or even dual discs. However, that's a personal choice that you're free to make. Co-Motion, on the other hand, must apply a level of conservatism as an OEM and that's what forms the basis for their recommendations."

    I know this thread is old but I am interested in the subject since I have a Santana Team Alu and am thinking of adding a rear disc brake to it since the wheel is disc ready and so it the frame. But I am not sure if the Avid BB7 will mount to the Santana disc brake caliper mount or not or if some special adapter is required for the Santana. As to the WinZip 10", if they really are not much more robust than the Avid BB7, then why not go for the Avid since they can be had for about $50.

    Does anyone know if this is an easy bolt on application?

  7. #7
    hors category TandemGeek's Avatar
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    Quote Originally Posted by slattekd View Post
    Does anyone know if this is an easy bolt on application?
    Yes, the 203mm Avid is a bolt-on for your Santana. However, the 203mm rear disc is not a standard package from Avid. You must typically buy the Avid Road disc set and then buy a 203mm rotor and 203mm caliper adapter.

    An early adopter was Bryan B. from Colorado and you can find his conversion process outlined here:
    http://www.precisiontandems.com/avidconversion.htm

    Best bet for determining exactly what you'd need for your model year Santana would be to call and speak with Mark Johnson at Precision Tandems, as he's spent a lot of time working up disc conversions for just about every model year Santana, e.g., http://www.precisiontandems.com/catframepart.htm

    Phone: 913-962-8866
    Central Time: 10 a.m. - 9 p.m.

  8. #8
    Senior Member antiquepedaler's Avatar
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    [QUOTE=TandemGeek;10433958]Yes, the 203mm Avid is a bolt-on for your Santana. However, the 203mm rear disc is not a standard package from Avid. You must typically buy the Avid Road disc set and then buy a 203mm rotor and 203mm caliper adapter.

    The 203mm rear disc IS a standard package on the MTB Avid BB7 disc brake. The MTB brake bolts up exactly the same as the road version. Got mine new off ebay for $40 including brake and 203mm disc to replace the well-used old one. I can't see any difference between the road and MTB versions except the color.
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  9. #9
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    The road caliper and mtb caliper are designed for different amounts of cable pull. Sram/Avid dont package the road caliper with the 203 bracket/rotor for consumer purchase.
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  10. #10
    hors category TandemGeek's Avatar
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    Quote Originally Posted by antiquepedaler View Post
    I can't see any difference between the road and MTB versions except the color.
    I'm not sure what you installed them on or what you may have had to do to get them adjusted to replicate the brake-lever to caliper mechanical advantage you had with the Road model, but as dfcas noted the Road version uses an internal cam calibrated for the 2:1 lever pull mechanical advantage found in drop-bar aero levers, e.g., STI, Ergo whereas the MTN version uses a cam calibrated for the 4:1 lever pull mechanical advantage found in V-Brake compatible levers. The only visual cue to the difference is the normal open position of the actuating arm, as you can see in the side-by-side photos below.

    Now, you can certainly make a MTN caliper work with drop-bar aero brakes if you use a V-brake adapter (which when used one way converts 2:1 road levers into a net 4:1 pull ratio) or by simply pre-loading the heck out of the actuating arm. However, the latter will give you very little brake power given the paltry amount of mechanical advantage that will net out from the short actuating arm travel.
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  11. #11
    Senior Member joe@vwvortex's Avatar
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    When I ordered my CoMo Speedster in 2004, I had it spec'd with a rear Avid disc, but also had V-brake and Arai Drum brake bosses put on as well. I have all the bosses/cable guides necessary to run both a V-brake and drum or disk. If I do ever run rear V-brakes though - I would only do it with a drum.

    Instead of not getting the steel fork with the Wound Up CF upgrade - I got both - so I could have the steel fork with mounts for panniers. Front disc brakes were not an option at the time so it have V-brakes. If I had the choice though - I'd have discs front and rear - but at this point the cost to upgrade to a new WoundUp Fork and disc compatible front wheel isn't worth it to me.
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  12. #12
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    Quote Originally Posted by TandemGeek View Post
    I'm not sure what you installed them on or what you may have had to do to get them adjusted to replicate the brake-lever to caliper mechanical advantage you had with the Road model, but as dfcas noted the Road version uses an internal cam calibrated for the 2:1 lever pull mechanical advantage found in drop-bar aero levers, e.g., STI, Ergo whereas the MTN version uses a cam calibrated for the 4:1 lever pull mechanical advantage found in V-Brake compatible levers. The only visual cue to the difference is the normal open position of the actuating arm, as you can see in the side-by-side photos below.

    Now, you can certainly make a MTN caliper work with drop-bar aero brakes if you use a V-brake adapter (which when used one way converts 2:1 road levers into a net 4:1 pull ratio) or by simply pre-loading the heck out of the actuating arm. However, the latter will give you very little brake power given the paltry amount of mechanical advantage that will net out from the short actuating arm travel.
    Is it possible to switch the internals on the calipers so that I can have road internals with the black Mtn externals?

  13. #13
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    After reviewing the Avid tech manual I do not see any reason a black BB7 could not be outfitted with the internals for the BB7. I will get some on order and let you know how it goes.

    BTW the color scheme of the chichi tandem is black and red always looking for an opportunity to get rid of bits that are the wrong color

  14. #14
    hors category TandemGeek's Avatar
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    Quote Originally Posted by chichi View Post
    I will get some on order and let you know how it goes.
    Wouldn't it be easier to just paint the caliper body and actuating / torque arm with some high-temp brake caliper paint? Oh wait, never mind.... Where's the fun in cheap and easy.

  15. #15
    Senior Member antiquepedaler's Avatar
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    [QUOTE=TandemGeek;10440504]I'm not sure what you installed them on or what you may have had to do to get them adjusted to replicate the brake-lever to caliper mechanical advantage you had with the Road model....

    Tecktro long-pull levers. They replaced Dia-Compe 287Vs because the axle pins wore out. I replaced troublesome Shimano STI with barend shifters and long pull brake levers several years ago.
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  16. #16
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    Quote Originally Posted by TandemGeek View Post
    Wouldn't it be easier to just paint the caliper body and actuating / torque arm with some high-temp brake caliper paint? Oh wait, never mind.... Where's the fun in cheap and easy.
    I have never tried painting componenets, I would be concerned that paint would peel off at contact points or break down from lubricants or cleaning. If anyone has had sucess with a particular painting method maybe I should think about painting the rear derailer?

    Painting the rear derailer would leave the FR and the S&S rings as the last remaining "bright" pieces, I can't imagine it would be practicle to paint those.

  17. #17
    Senior Member joe@vwvortex's Avatar
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    Quote Originally Posted by chichi View Post
    I have never tried painting componenets, I would be concerned that paint would peel off at contact points or break down from lubricants or cleaning. If anyone has had sucess with a particular painting method maybe I should think about painting the rear derailer?

    Painting the rear derailer would leave the FR and the S&S rings as the last remaining "bright" pieces, I can't imagine it would be practicle to paint those.
    Prep is critical in painting but if the right paint is used and it's done correctly - there should be no problem with it.
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  18. #18
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    I made the conversion from the winzip to the mtn not knowing the difference (I wanted the black) left the 10" rotor on and works great. I do have a advance gizmo that came with the stock bike.

    I know that Ric at House of Tandems does the conversion with the road version.

    http://houseoftandems.com/page.cfm?PageID=72

  19. #19
    hors category TandemGeek's Avatar
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    Quote Originally Posted by antiquepedaler View Post
    Tecktro long-pull levers. They replaced Dia-Compe 287Vs because the axle pins wore out. I replaced troublesome Shimano STI with barend shifters and long pull brake levers several years ago.
    So, I would have to assume if you were using the BB7 Road with your 287Vs and Tektro V-brake levers you, (a) had some short lever travel & massive mechanical advantage / brake clamping, (b) simply allowed for a lot of pad clearance at the rotor to off-set the high M/A of the V-brake levers or, (c) used a Travel Agent in it's 'b' configuration to reduce the M/A of the lever pull. My guess would be (b), which netted you performance that would be similiar to someone running STI / Ergo levers with a Travel Agent in it's 'a' configuration & a BB7 Road.

  20. #20
    hors category TandemGeek's Avatar
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    Quote Originally Posted by joe@vwvortex View Post
    Prep is critical in painting but if the right paint is used and it's done correctly - there should be no problem with it.
    What he said... OR, (a) plan ahead next time and buy components based on their color, (b) make friends with someone who does anodizing and/or powdercoating, (c) or don't spend so much time looking at your bike.

  21. #21
    hors category TandemGeek's Avatar
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    Quote Originally Posted by 2592 View Post
    I do have a advance gizmo that came with the stock bike.
    So long as the Travel Agent or a BPB is in the cable run to modify the mechanical advantage of the lever, either the BB7 MTN or BB7 Road will work. After all, BB7s were originally available and found their way onto tandems early on only as a MTN version. The Road version came out later and eliminated the need for klugy solutions... we sort of. Booster springs and careful attention to the cable runs, housing stiffness, rotor trueness and brake pad clearance / set-up were and still are critical to good performance without rotor rub.

  22. #22
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    Quote Originally Posted by TandemGeek View Post
    Based on following this issue for over a decade, personal experience and discussions with the folks in the industry three reasons seem to rise to the top:

    [INDENT]1. For loaded touring or any other heavy-duty requirements where constant braking would be required on a long, steep or long-steep descent, Co-Motion's recommended set-up has been proven over time to be the most effective. The reason for this is straight forward: the Arai drum is an application specific supplemental 'drag-brake' designed to deal with very high heat loads and that works in parallel on a non-interference basis with rim brakes. Note: At present, no one has designed a disc rotor with an integral drum brake so the use of one precludes the use of the other.
    The Arai may be a great product, but be aware that production has ceased a little while ago. It's still in stock at retailers/builders but these stocks are not endless.

    FWIW: We have an MTB tandem with dual Hope Mono6ti disc brakes for loaded cycle touring. These brakes are very powerful and never ever let us down on Alpine descents or anywhere else. It must be added that we only weigh 300 lbs together. We also own a C'dale RT with the dual Avids but this bike is only used for touring so brake performance has never been an issue.
    Regards, Marten / www.tandemclub.nl
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