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  1. #1
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    Mechanical discs vrs V-Brakes

    Not long bought our Cannondale Road 3 tandem, which we're really pleased with. But as per usual, can't resist changing bits, mainly to save weight. I'm thinking of ditching the Avid mechanical discs what were fitted originally and using Shimano XTR v-brakes. Just wondered if this is a big mistake and we'd struggle to stop on steep descents? Our combined weight is a little less than 300lbs. Your thoughts are most welcome.
    Last edited by Amesbub; 08-13-09 at 06:01 AM.

  2. #2
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    Welcome to the forum and congrats on the new C'dale.
    Your question is a very popular one that has been asked in various ways and covered hundreds times here. IF you play with the 'search function' a little you will be reading for days...Ultimately you will find that people swear by both for different reasons. Both are good, but your priorities, where and how you ride, along with your past experiences will probably define what will be best for you...Have fun and enjoy the ride.

    Bill J.

  3. #3
    Senior Member rdtompki's Avatar
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    I wouldn't bother to change. Let's say total weight of team and bike is 350 lbs full up. A 10 mph climb ignoring aero effect woud net you a speed increase of .03 mph assuming a 1 lb weight penality for the disc. I supposed a disc has more aero drag than a v-brake so there might be a penalty at high speed, but I have no idea what that would be.
    Rick T
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  4. #4
    Senior Member DCwom's Avatar
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    My 2 cents, about what its worth since we don't do hills...

    We have v-brakes, and I wish I had a disc to drag on the rear, not that we're climbing hills large enough to overheat our rims, but I'm just paranoid about it. Every time we experience a new down hill I think how long is this, will this be a hill worthy of stopping to check the rims? As for the weight, if I was concerned about another pound on the frame, I'd go on a diet, which of course would reduce the chance of my rims heating...

  5. #5
    Senior Member Retro Grouch's Avatar
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    Oh good! I thought that I was the only guy left who wasn't enchanted with disc brakes. If my Noventa had a place to put it, I'd ditch my WindZip rear disc and stick on an Avid SD7.

    Having said that, if you are dissatisfied with the stopping power of your mechanical discs, hunt up some compressionless BRAKE housing. It's out there and it makes a huge difference.

  6. #6
    Senior Member WebsterBikeMan's Avatar
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    Alternatively, if you do want to switch, you might want to wait until it's time to change the pads anyhow. Struggling to stop isn't the issue on steep descents. The question is whether you overheat while avoiding going faster than you wanted. That's where drag brakes come in. Touring, we come in at around 400 including riders, bike, 60 lbs gear, and 3l water. We managed to stop after coming down from the Watkins Glen Campground (60m drop, 400m horizontal with stretches of 20% with a speed limit 25 mph, and a stop sign at the bottom). The problem was avoiding exceeding the speed limit by too much without overheating the rims. Mind you we do have Aeroheat rims, which seem to be better than some as far as that goes.

    Much depends on what you mean by steep.

  7. #7
    Senior Member Brian's Avatar
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    So you want to switch from tandem rated discs to XC racing brakes?

  8. #8
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    Quote Originally Posted by Brian View Post
    So you want to switch from tandem rated discs to XC racing brakes?
    Just to be clear, the last time I checked with Avid their discs were not approved for tandem use. I've gotten better performance with rim brakes than disc, but my Avid disc may have been defective. You could shave some real weight by installing a carbon fork (Reynolds or Alpha Q) with a caliper brake.
    In a previous post you have a picture of some wet riding. The discs will work better when wet.

  9. #9
    Senior Member Brian's Avatar
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    Quote Originally Posted by justcrankn View Post
    Just to be clear, the last time I checked with Avid their discs were not approved for tandem use.
    What's your source? When I put them on my tandem MTB, I did so because they were the only mechanical discs rated for tandem use.

  10. #10
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Brian View Post
    What's your source? When I put them on my tandem MTB, I did so because they were the only mechanical discs rated for tandem use.
    I believe the pendulum has swayed back and forth a bit over the years.

    1. The Avid's were initially not endorsed for use on tandems when they first were introduced and Avid was still Avid (late 90's).

    2. After some extensive use of the BB7s on both off-road and road tandems with excellent results and no safety issues by a well-respected tandem builder co-located in the same part of the same Colorado town, Avid BB7s were spec'd as OEM brakes on Cannnondale's 2004 RT3000 tandems shown at the '03 Interbike and were shortly thereafter offered as an optional front and/or rear brake on Co-Motion's tandems. The Avid's came with the following caveats: (a) only when used with the 203mm rotor, and (b) only when used as a direct replacement for a primary rim brake. The latter basically said, these are as good or better than rim brakes but they're not suitable as a drag brake replacement for the Arai drum. None of this was covered in any literature, it was communicated they way most technical information was within the tandem community via OEM endorsement and one-on-one phone calls with Avid's tech dept.

    Note: Bear in mind that you won't find any rim brakes that are "rated" for tandem use either.

    3. During Interbike '03 (when Cannondale showed up with the '04 model-year Avid-equipped RT3000) a certain OEM builder who chose not to offer Avids began a subtle campaign to label the Avid's as not being tandem-rated and went to far as to suggest that C'dale was putting itself at risk by spec'ing the Avids. Given that to this day some 5 years later (or thereabouts) Cannondale with all of it's corp. lawyers and past liability issues on early frame failures still spec'd the Avid's so take that for what it's worth. Similarly, Co-Motion, daVinci and a few other builders also offer the Avid as an optional primary brake on road and/or off-road and enduro tandems.

    4. When SRAM acquired Avid the tandem endorsement didn't seem to carry over to the new company's marketing or tech departments in their list of approved answers to FAQs.

    Again, there's not much in the way of bicycle components that are designed for use on tandems and/or that carry tandem endorsements. Therefore, we look to the OEMs and early adopters of new component offerings to find out what seems to work and what doesn't. Thus far, Avid's BB7 discs with the 203mm rotors have enjoyed a pretty darn good track record with any "failures" being limited to melted adjustment nobs (not a critical component) or other types of failures such as brake fade or warped discs that are on par with the problems teams have when they push rim brakes beyond reasonable expectations, e.g., loads, conditions or method of use.
    Last edited by TandemGeek; 08-20-09 at 11:01 AM.

  11. #11
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    Quote Originally Posted by Brian View Post
    What's your source? When I put them on my tandem MTB, I did so because they were the only mechanical discs rated for tandem use.
    Phone call several years ago. My LBS called and they wouldn't offer any support for a tandem. Here's their contact page http://www.sram.com/en/about/contact.php if you want to call.
    I have no doubt that the Avid would be the best choice for a road disc, but that doesn't make it "tandem approved".
    IIRC Avid did approve them for awhile. Searching the archives might pull up more info.

  12. #12
    Senior Member Brian's Avatar
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    I read that test years ago where brakes melted and fluid boiled, and Avids came out on top.

    [edit] I have reliably used them on a tandem with 350+lbs of captain/stoker.

  13. #13
    so cal com John R's Avatar
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    I did Everest Challenge on 07 with Avid shortys cantis with no problems.
    Pain is Weakness Leaving The Body[SIGPIC][/SIGPIC].

  14. #14
    I'd rather be riding DKMcK's Avatar
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    I purchased my 05 Cannondale last year from someone who had already done the weight reduction upgrades (carbon fork, Avid shorty breaks, lighter wheels, and a few others). Our Cannondale weighs in at just over 34lbs. He also threw in the removed components in the deal. I'm really happy with how the bike rides. I did replace the Avid Shorty on the rear with a v-break, the shorty just did not work well with the long cable. We had some long descents on the Bike Virginia ride this year and I was wondering if I should have but the discs back on. I never felt like i could not stop but was concerned about heat buildup. Probably more worry than reality. We do not live in the mountains and my stoker has made it very clear we're not riding in the mountains, so this setup works great for us. I suspect the carbon fork is the best "bang for the buch" upgrade. It saves weight and improves the ride.

  15. #15
    Tandem Mountain Climber
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    Quote Originally Posted by John R View Post
    I did Everest Challenge on 07 with Avid shortys cantis with no problems.
    Tandem or solo?

  16. #16
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    We have a Santana Arriva with V's t/agents (Koolstop dual compound pads)and STI's on drops, third brake is an Arai,the Arai is a boon in the big hills and the V's very good.
    Earier this year we bought a Cannondale Road tandem(C/dale only sell the disc equiped tandem in the UK)mainly as a winter bike to save on rims, the stopping power of the Avid BB7's is awesome in comparison with the V's and in the wet there is simply no contest, discs win hands down.
    The Santana will still be used on tours in the mountains where the Arai drag comes into its element but I'm very impressed with the discs.

  17. #17
    sch
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    Cantis work at least as well as BB7 discs with 203mm rotors and weigh ~120z per wheel less. We put
    a disc rear on ours when we found the wheel rim too hot to touch at the end of rides to my house
    when we braked from 35mph to 0 over ~200 yds with an elevation change of ~40'. There aren't any
    local hills longer than 2mi and the longest down hill in the state is perhaps 10mi, but this is a roller
    coaster. If your riding does not significantly heat the rims and does not involve a lot of water on
    the rims the cantis should be adequate. In our experience the BB7 pads last about 5 kmile, at a
    replacement cost in the $12-15 range. Canti pads last a lot longer, but off road riding will abrade
    the rims away over time.

  18. #18
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    Amesbub, if you convert to V brakes, can I buy your Avid discs? I just bought a Cannondale with V brakes and want to convert the other way (mainly because I'm converting the bike to 650b).

  19. #19
    so cal com John R's Avatar
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    On a Cannondale Tandem...
    Pain is Weakness Leaving The Body[SIGPIC][/SIGPIC].

  20. #20
    Twin Bicycles TwinBicyclesNY's Avatar
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    As a store owner, it will mainly depend on what kind of weather riding style you guys will be doing. If you ride your tandem all day every day every weather then i would keep the disc brakes on and ditch the XTRs. If you only happen to ride when most normal people ride in a beautiful weather settings, you can go either or. Of course the XTRs will help in saving weight on your bicycle. IMO, disc brakes and v brakes are pretty much the same in the sunny, dry conditions. I hope this helps and keep on riding.

  21. #21
    Senior Member zonatandem's Avatar
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    Save some weight . . .
    Keep rear disc and V-brake up front.

  22. #22
    pan y agua merlinextraligh's Avatar
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    Quote Originally Posted by Amesbub View Post
    . Just wondered if this is a big mistake and we'd struggle to stop on steep descents?
    The issue isn't stopping power. Good rim brakes will stop a tandem as well as discs. Once you have the power to lock the wheels (and modulate short of that) brakes can't give you anymore stopping power.

    The issue is heat. Lots of braking on steep descents can overheat rims,a nd lead to tire failure. The likelyhood of this depends on 1) the total weight (including bike, riders, and cargo, 2) the terrain, and 3) riding style.

    For us, at a team wieght around 350lbs, we've found rim brakes adequate even in steep and long descents. But we tend to descend fast, and only brake for turns, which allows the brakes to cool between turns. If you want to control your speed more, and are riding technical terrain, you might want discs.
    You could fall off a cliff and die.
    You could get lost and die.
    You could hit a tree and die.
    OR YOU COULD STAY HOME AND FALL OFF THE COUCH AND DIE.

  23. #23
    Senior Member WebsterBikeMan's Avatar
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    Quote Originally Posted by merlinextraligh View Post
    The issue isn't stopping power. Good rim brakes will stop a tandem as well as discs. Once you have the power to lock the wheels (and modulate short of that) brakes can't give you anymore stopping power.
    +1
    Quote Originally Posted by merlinextraligh View Post
    The issue is heat. Lots of braking on steep descents can overheat rims,a nd lead to tire failure. The likelyhood of this depends on 1) the total weight (including bike, riders, and cargo, 2) the terrain, and 3) riding style.
    And rims and probably tires. Some rims have more mass further from the tire (Velocity Aeroheats/Aeroheads come to mind, as do Deep V's). Wire bead tires may be more likely to conduct the heat to the tube. Wider tires can absorb more heat as well. All of which are probably second order effects to the ones already listed. You have to dump a certain amount of energy, and it all goes into heat.

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