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  1. #1
    Senior Member Lost Coyote's Avatar
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    Front disk setups

    Well much to my surprise, while celebrating our anniversary the other night, out of the clear blue sky my wife suggested that we should get a tandem! Woo hoo! So, Iím in the process of evaluating components and set ups for building a road tandem.

    My wife has spent very little time on a tandem and Iíve got a dozen or so rides in as a stoker. I ridden on a Santana with a rear Formula hydraulic hybrid disk, but the owner took it off after too many headaches and problems. Last weekend the same guy suffered a front tire failure due an overheated rim on a downhill we commonly ride. Iíve read through the forum and have the following questions for you folks:

    Why am I not finding anything information about font disk brakes? With so much of the braking force being on the front why isn't all the stuff learned from mountain biking disk systems being applied to tandems? Is it that no one makes a system that is compatible with existing Shimano or Campy levers? Also does anyone even make a tandem road fork for disk brakes?

    Thanks in advance
    Gravity kills.

  2. #2
    hors category TandemGeek's Avatar
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    At present, the biggest problem is the lack of any mechanical disc brakes that are approved / warrantied for use on tandems by their manufacturers.

    However, that said, there are at least two builders -- Todd Shusterman, dba daVinci Designs (www.davincitandems.com) and Glenn Erickson, dba Erickson Cycles (http://home.att.net/~debbie.livingoo...onTandems.html) -- who have been building tandems with front & rear primary mechanical disc systems. The Avid BB mechanical disc is at the heart of their systems and the road model works with both Shimano STI and Campy Ergo levers. However, both builders make their own custom forks for use with the disc brake systems as there are no commercially available ones that are suitable. It is quite possible that Dennis Bushnell (http://www.sandsmachine.com/bp_bushn.htm) may also be making tandems that are disc-brake equipped as he and Glenn Erickson have a very close working relationship.

    Thus far, I have only inspected and worked on one of Glenn's disc brake tandems... one that was recently delivered to some friends here in the Atlanta area. Glenn is riding another one on his tours in Europe and is really enthusiastic about their performance. I believe he may have built 2 or 3 other dual-disk tandems this past year. Todd has been using the dual disc system for at least two years, having tested it last year in Europe on his personal tandem with much success. He also outfits his off-road tandems with the Avid BB disc brakes and, again, thus far the results have been very good.

    Notwithstanding these favorable results, I'd have to say that the use of dual discs on tandems is definitely in the "beta test" phase. In other words, if you're riding one of these bikes you are on the "bleeding edge" of the development cycle and are -- in fact -- a test pilot/team. There are some serious safety issues with how you mount and secure the front wheels on disc-equipped tandems and bikes and fortunately, both of these builders have been able to address these issues in the design of their forks. But, keep in mind, there isn't a whole lot of field testing data available to quantify the long-term reliability or durability of these designs.

    Bottom Line: It's possible, it's being done but there are many issues to consider before taking the plunge.
    Last edited by TandemGeek; 01-30-05 at 08:55 PM.

  3. #3
    Senior Member Lost Coyote's Avatar
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    Thanks for the reply.

    I must say Iím a little amazed with lack of products available for tandems with the apparent acceptance of disk technology in the mountain biking community. I did read up on the QR/disk brake safety issues, and yes it would be pretty traumatic to have your font wheel fall off at speed!

    Why is it do you suppose that disk set ups are just emerging on tandems? Could it be the market size isnít large enough to support the effort? I would like to see a higher quality (less problematic) system than found with the Formula products. Bottom line is Iíd hate to build a bike now, only to find that 6 months from now a good quality system hits the market and Iíd have to retrofit my new bike!

    If it were built, would they come?

    Again thanks for the reply and the links!
    Gravity kills.

  4. #4
    hors category TandemGeek's Avatar
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    First: Keep in mind, tandems are an incredibly small niche market that relies on trickle-down components and technology. Independent R&D by tandem builders is nearly non-existent on any significant scale compared to more mainstream bicycle product development. After all, only one bicycle out of 10,000 manufactured each year is a tandem; not a lot of volume / margin to play around with for R&D.

    Second: Back to trickle-down technology, there aren't too many road bikes using disc brake technology just yet. Giant is marketing a touring bike with discs but that's about it so tandems really aren't lagging behind the marketing trends (and, after all that's what drives development). However, disc brakes have been used on off-road tandems for several years which makes sense because disc brakes have significant advantages for off-road applications and their use across the entire off-road market is quite purvasive. Back to the tandems which rely on trickle-down technology, disc brakes only became practical for use on tandems when the Downhill racers created a need for high-heat tolerant disc brake systems that used open systems (i.e., master cyclinders that allow for heat expansion of the brake fluid) and high-temp DOT brake fluids vs mineral oil. As a result there are several open hydraulic disc brake systems available that are approved and warrantied for tandems: Hope's Enduro's & Magura's Gustav M and Julie. Some builders and private parties are also using the Avid BB mechanical systems and Hayes Open hydraulic systems but without warranty coverage and the endorsement of the manufacturers. Now, having used several of these systems I can tell you they still aren't quite perfect. We have successfully boiled our DOT high-temp brake fluid and seized Hope's 04DH and Enduro models of hydraulic disc brakes on our off-road tandem a couple times because tandems with two riders are just a heck of a lot heavier and harder to stop than single bikes. So, as good as these "approved" open system brakes are they were not developed for tandems; they are just "adaptable" with some limitations and a failure mode that's considered "safe", e.g., the brakes lock-up instead of failing.

    Third: If they build them will people buy them? Good question. Right now, my personal take is I'd be reluctant to outfit my tandem with disc brakes front & rear. I wouldn't object to having an Avid as a primary rear brake fitted to a tandem for use in the mountains in lieu of a drag brake. However, I'd probably specify that it retain cable guides and a brake bridge so that I could fit a brake road brake caliper for every day riding. This probably reflects a general consensus for some builders as Santana pioneered the use of the full-time rear disc several years ago (actually, a customer asked for it first and Santana adopted it) and the Avid mechanical disc is offered as a full-time, primary rear brake on Co-Motion's tandems (not as a drag brake). As I already mentioned, Glenn & Todd are building tandems with front discs and while I can appreciate the benefits I'm not sure I'm sold on them for fast recreational tandems or for travel bikes due to the weight penalties, the inability to use a carbon fork with them and potential issues you'd run into finding replacement parts and/or rims away from home. After all, as it is now, if you trash a front wheel you can pretty much use any OTS 36h 700c wheel to get you back on your way. Try finding a 700c disc wheel laying around or a Ritchey off-set 700c rim at your LBS or, better yet, in France while on tour in the mountains.

    Bottom Line: Anything is possible with a tandem, but everything's not practical. Time has a way of sorting out which is which.
    Last edited by TandemGeek; 01-30-05 at 08:55 PM.

  5. #5
    Senior Member Lost Coyote's Avatar
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    Well put Mark, thanks for the reply. Iíve always been a DIY kinda guy, so a brake system that lacks warranty coverage and the endorsement of a manufacturer is not an issue for me. (Iím not the kind who would look for someone to blame or sue if it failed anyway). I was looking more at available components that I could use to when building my bike.

    My wish would be to be able to adapt a DH hydraulic disk set up. However, there seems to be a lack of shifters/brake levers made for drop bars that can be used with hydraulic systems. If I were to go with a flat bar, simply using XTR shifter/levers would be a perfect match. (but a flat bar ainít gonna make it on my road bike.) Cyclocross appears to be the only other group besides tandems who use drop bars and disk brakes. Most of ďcrossĒ guys seem to be using the Avid mechanical system for road bikes with Ultegra/105 shifters/levers. Iím not sure that the Avid road disk would be ďbeefyĒ enough for a tandem. My research shows that trying to use a heavy-duty Hayes DH mechanical system wonít work with the road levers due to amount of cable pull required. (Similar to the problem found when mismatching levers for cantilever and side pull breaks). I guess you could make an actuator arm of the proper length to get the cable pull right but geeze thatís starting to get a little too complex isnít it?

    I appreciate your comments regarding practicality. A home brewed bastard might be fine for weekend rides around town but could be problematic when traveling. Again, thanks for the comments, Iíll let you know what I end up with.
    Gravity kills.

  6. #6
    SDS
    SDS is offline
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    Was there an announcement a while back that Magura was going to start supplying an STI lever that worked with their hydraulic disk brake?

  7. #7
    hors category TandemGeek's Avatar
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    Originally posted by Lost Coyote
    My wish would be to be able to adapt a DH hydraulic disk set up.
    You really don't want hydraulic discs on a road tandem; far too many problems, constraints and weight penalties vs the benefits that hydraulics provide over Avid BB mechanical discs. In fact, the Avid BB performance is so good that one of the emerging problems with disc brakes on road bikes and tandems will be hazardous situations where a disc brake equipped bike is ahead of and easily out-brakes non-disc bikes on fast descents... it could get ugly.

    Most of ďcrossĒ guys seem to be using the Avid mechanical system for road bikes with Ultegra/105 shifters/levers. Iím not sure that the Avid road disk would be ďbeefyĒ enough for a tandem.
    At present, the Avid is the only mechanical system that I would personally consider. As evidenced by the cyclocross users set-ups, Avid does make a drop bar STI / Ergo lever-compatible model of its Avid BB disc caliper. Hayes does not and a brake-booster or other modifications are required to allow their use with STI/Ergo that reduce reliability.

    Bottom Line: If you intend to go the disc brake route use the Avid BB mechanical disc brake (road version).

    Additionally, spend some time on the phone with Todd Shusterman, share some Email with Glenn Erickson (he's in Europe leading tours until November so phone calls aren't practical), or perhaps touch base with Dennis Bushnell. You can talk to the folks at Avid but talk with Todd first to get the name of the right guy to talk to (daVinci & Avid have been working closely on the disc brake applications and are physically located near each other).

    FWIW: Here's what seems to work....

    The preferred configuration that is used for rear discs is 135mm or 145mm rear drop-out spacing since the IS disc mounting standards and almost all available disc systems are designed for the 135mm MTB rear drop-out spacing. Nothing special required for the rear installation.

    Front spacing is 110mm. For the front brake installation, a custom made steel fork with steel steerer is used. The disc caliper is mounted "backwards" on the front of the right fork blade so that the brake energy drives the front wheel axle back and up into the fork drop-out. This requires the front wheel to be built backwards as well and if the disc rotor is uni-directional it also must be mounted "backwards". The alternative to the backwards installation would be to fabricate a fork with massive lawyer lips or with the drop-out opening rotated back and up, neither of which is desireable and both of which have less than desireable failure modes.

    As for wheels and hubs, a standard front disc hub is used. For rims, what I worked on was a set-up using Velocity's 700c Aerohead off-set rim which allows the front wheel spoke lacing to be nearly symetrical, aka, dishless. If you use a standard rim you will end up with a dished front wheel.

    Good hunting....

  8. #8
    hors category TandemGeek's Avatar
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    Originally posted by SDS
    Was there an announcement a while back that Magura was going to start supplying an STI lever that worked with their hydraulic disk brake?
    Not that I'm aware of. Edco made a very limited run of an integrated shift/brake lever that was compatible with Magura's HS-66 rim brakes but that's all that comes to mind.

    The HS-66 is their hydraulic rim brake system for drop-bars and it uses non-integrated "aero" brake levers in combination with either down-tube or bar-end shifters. It is not STI/Ergo compatible nor is it designed for use with their disc brake systems (nor is/was the Edco system).

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