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  1. #1
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    Tandem rim brakes

    I bought a 1991 GF Gemini a couple months ago. I've been riding it on roads and easy trails, mostly with my buddy. Together we weigh 410lbs (6'3 and 6'5, yeah we look super goofy), and the canti brakes get a serious workout. If we had more powerful and especially fade resistant brakes there are a lot more trails we could take the bike on.

    I currently have canti brakes that have been adjusted for maximum leverage and minimum rim clearance, and the rear ones are those self-energizing design that ratchet themselves tight. I have them nicely adjusted, but brake fade puts the levers in to the bars in a big stop, which is disconcerting. I have Koolstop salmon pads.

    I was reading on the Santana website about how much they love avid SD7s. I don't really wanna pour a bunch of money in to this bike, it's just for fun, but those seem reasonably inexpensive and if they opened us up to more rides that would be cool. In my experience well-tuned cantis don't really lose anything to Vs, though, so i have my doubts.

    I'd welcome any other advice about getting the most out of the brakes, too.
    .

  2. #2
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    Do SD levers work with canti brakes?
    If so, they are def. great bang for the buck.

    We were up to 460# with the tandem + trail-a-bike. That felt like the max weight for rear V-brakes with front 203mm BB7 for speeds over 20mph. It just took too long to stop on the road.
    On trails, I felt a lot better since we didn't have so much momentum. If you can lock up the brakes at low speed (read: test them first), a few steep grades won't bother you unless they are long grades. If you can build any speed, or you get wet, you will outrun your brakes.

    Don't forget your helmets.

    -F
    It's never easier - you just go faster.

  3. #3
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    Quote Originally Posted by Fleas View Post
    Do SD levers work with canti brakes?
    If so, they are def. great bang for the buck.
    I think there's a variety of sd7 levers with adjustable pull ratio, so those would work. I have some sd5 levers in a box. I have these huuuge moto levers on there now, and i like the leverage they offer. I don't think there's much to be gained on the lever side, i'd just run the levers that correspond to the brake.

    Quote Originally Posted by Fleas View Post
    We were up to 460# with the tandem + trail-a-bike. That felt like the max weight for rear V-brakes with front 203mm BB7 for speeds over 20mph. It just took too long to stop on the road.
    On trails, I felt a lot better since we didn't have so much momentum. If you can lock up the brakes at low speed (read: test them first), a few steep grades won't bother you unless they are long grades. If you can build any speed, or you get wet, you will outrun your brakes.

    Don't forget your helmets.

    -F
    That's a fairly different situation, actually. Our last after-work ride did 2500' of climbing and hit 44mph on a road descent. Wheeee! Trails around here are steep, and even a ~300' off road descent cooks the pads pretty badly. Part of that is because i don't wanna 'let it run' because the stopping distance is poor. The brakes are pretty taxed on what are already easier rides.

    The way they're set up, i can lock both wheels in the dirt if the pads are dead cold. As soon as they warm up... not so much, and the squishiness of the pads/ high leverage means the levers bottom out on the bar.
    .

  4. #4
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    You're exceeding your brake setup's ability to bleed off heat. I don't see how a different lever is going to fix that. You may be able to clamp the pads tighter with a different brake setup, but that doesn't seem to be the problem (since you have acceptable performance when cold), and obviously once they get hot clamping tighter will be of no benefit.

    Santana is focused on road tandems. We have a road tandem with old V brakes and have never had a problem with braking performance, and have hit 45mph on the downs. We had a HT mountain tandem with rim brakes and, like you, those brakes dramatically limited our speed on beginner trails.

    You indicate your brakes are already taxed on your easy rides. Getting a disc fork, brake, and front wheel setup isn't too spendy, especially considering where you are WRT brake performance.

  5. #5
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    Quote Originally Posted by Okayfine View Post
    You're exceeding your brake setup's ability to bleed off heat. I don't see how a different lever is going to fix that. You may be able to clamp the pads tighter with a different brake setup, but that doesn't seem to be the problem (since you have acceptable performance when cold), and obviously once they get hot clamping tighter will be of no benefit.
    These are what i'm referring to.


    I was hoping they had a higher leverage ratio than i could dial in, combined with less compressible pads. I don't really know.
    Quote Originally Posted by Okayfine View Post
    Santana is focused on road tandems. We have a road tandem with old V brakes and have never had a problem with braking performance, and have hit 45mph on the downs. We had a HT mountain tandem with rim brakes and, like you, those brakes dramatically limited our speed on beginner trails.

    You indicate your brakes are already taxed on your easy rides. Getting a disc fork, brake, and front wheel setup isn't too spendy, especially considering where you are WRT brake performance.
    It's a fisher from the 1 1/4 era. It has a weird head tube diameter. I have a short travel freeride fork i could put on, but as a big dude i'm not convinced a disk brake will offer a larger heat sink anyway, and the limited reading i've done supports my experience. In my limited experience the rigid fork is pretty great on the tandem- i don't need a suspension fork for the trails we're riding, and half the time it's road rides.

    My freeride fork, a 130mm manitou sherman with an xfirm spring, would raise the front end a bit even after it was megasagged. I figure that won't matter much as far as fit and handling, since the bike is so long, but i don't need a suspension fork for what i'm doing. (and rigid is just cool)

    It's worth noting i got my tandem in basically-new condition for 350$. I'm not a real tandemist, i just wanna be able to ride the bike anywhere our skills will take us.


    I noticed koolstop has grey pads designed for ebikes and clear pads designed for trials. Has anyone tried those? It doesn't look like they have a canti option...
    .

  6. #6
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    Quote Originally Posted by scottzg View Post
    It's a fisher from the 1 1/4 era. It has a weird head tube diameter.

    but i don't need a suspension fork for what i'm doing. (and rigid is just cool)
    Don't gotta switch to a suspension fork. Lots of framebuilders these days that will make you a custom fork to the specs you need, including a disc tab and 1.25 steerer. And for less money than the cheapest tandem-rated suspension fork. Walt has done work for a team or two in this forum.

    Quote Originally Posted by scottzg View Post
    i just wanna be able to ride the bike anywhere our skills will take us.
    You're currently limiting yourselves to rides you think the bike can handle, and you are already exceeding what your bike can handle.

    You're hitting up against and exceeding the heat-dissipation limits of your current brake setup. The different parts you're talking about aren't really going to change that, you're generating sufficient friction, but the heat generated as a result can't leave faster than you're creating it.

    Time to upgrade to disc. At least in the front. And the rear is easier and cheaper:
    Brake Therapy Conversion Kit

  7. #7
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    Okayfine, that Brake Therapy Conversion looks COOL! Might have to do that on the Santana.

    Scott, as Okay says, sounds like you're well past the capability of rim brakes. Not sure where you got the idea that disk brakes aren't convincingly better, but I'm pretty sure everyone here who rides discs will assure you that there is no comparison.

    From your description, it sounds like a big disc (203 mm) and beefy calipers are in order [edit ... looks like the Brake Therapy will only take a 160]

    Remember, money is just money, fun is FUN! and it sounds like you're having LOADS of fun on this rig, well worth investing, imho. Cheers
    Last edited by ki5ka; 11-01-2014 at 02:42 PM. Reason: correction

  8. #8
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    Quote Originally Posted by Okayfine View Post
    Don't gotta switch to a suspension fork. Lots of framebuilders these days that will make you a custom fork to the specs you need, including a disc tab and 1.25 steerer. And for less money than the cheapest tandem-rated suspension fork. Walt has done work for a team or two in this forum.



    You're currently limiting yourselves to rides you think the bike can handle, and you are already exceeding what your bike can handle.

    You're hitting up against and exceeding the heat-dissipation limits of your current brake setup. The different parts you're talking about aren't really going to change that, you're generating sufficient friction, but the heat generated as a result can't leave faster than you're creating it.

    Time to upgrade to disc. At least in the front. And the rear is easier and cheaper:
    Brake Therapy Conversion Kit
    Yep, that's probably the most effective course of action, but i'm not doing that. Just the therapy kit is half what i paid for the bike, and i'm not willing to spend 700$ to put disks on a 20 year old bike.

    I think i'll dork around with the cantis a bit and just leave it be. I appreciate the input; you've put my head in the right place.
    .

  9. #9
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    Buy an ECdM! You'll NEVER regret it...

  10. #10
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    Quote Originally Posted by ki5ka View Post
    Buy an ECdM! You'll NEVER regret it...
    I finally looked that up... omg that looks fun. Considering how we can blast through some pretty tough stuff so long as it's not switchbacks... it's best i can't afford that much tandem.

    Half our entertainment is about how stupid we look. I pulled the bike out today and lubed the cables, reduced the preload on the cantis, and sanded the scott-mathauser pads it came with (since i couldn't locate some kool-stop salmon canti pads locally), and tuned in extra leverage and engagement. The rear brakes still honk like a goose, and i don't expect them to behave any differently, but when the brakes fail at least i won't die alone.

    How many of you out there have a tandem partner that isn't a SO?
    .

  11. #11
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    I read the posts quickly. Did not see mention of a frame and / or fork brace for the brake posts.

    These are fairly inexpensive, and will help if the frame is bowing out.

    Not sure on availability, but I have also made them as opposed to buying a universal one when I ran Magura rim crusher brakes.

    This was a big aftermarket item in the circa / vintage of your machine.

    PK
    Reps! We don't need no stickin' reps!

  12. #12
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    Quote Originally Posted by PMK View Post
    I read the posts quickly. Did not see mention of a frame and / or fork brace for the brake posts.

    These are fairly inexpensive, and will help if the frame is bowing out.

    Not sure on availability, but I have also made them as opposed to buying a universal one when I ran Magura rim crusher brakes.

    This was a big aftermarket item in the circa / vintage of your machine.

    PK
    Purchased. Good idea!
    .

  13. #13
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    Quote Originally Posted by scottzg View Post
    but when the brakes fail at least i won't die alone.
    That's the spirit!

  14. #14
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    [Atom lab rims are mega overbuild, massive but also very heavy, one good thing is that they dissipate heat like nobody's business (do to all the aluminum on them)



    Oh yeah brake boosters are essential my favorite DKG...

  15. #15
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    Quote Originally Posted by scottzg View Post
    ...

    How many of you out there have a tandem partner that isn't a SO?
    For a few years I rode occasionally with another guy. He would be the one pedaling on the downhills while I was braking in fear. Although I did get him to jump off when I took a hairpin turn onto a 10ft. high bridge. I made it. He watched. The amount of power we made as a team was ridiculous - and this was when trails were not IMBA-standard. We could really throw a rooster tail of mud!
    I also rode with a woman who was rehabbing a knee injury. Once she was back to 100% we rode hard, but not much tech. - just speed.
    Neither was ever as good as my wife, though. She had a knack from day 1.

    -F
    It's never easier - you just go faster.

  16. #16
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    Quote Originally Posted by Fleas View Post
    ....
    Neither was ever as good as my wife, though. She had a knack from day 1.

    -F
    Yep

  17. #17
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    TandemNut has talked about this before. US tandem teams are predominately SOs.

  18. #18
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    Been out the last couple rides with a 90lb stoker (adult female cyclist) instead of a 190lb one. Way better! Not only can we stop like a bus, we can track stand and pedal out of the saddle simultaneously! Much more fun, even if we don't have the silly flatland speed that 2 huge dudes can produce.
    .

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