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  1. #1
    Time for a change. stapfam's Avatar
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    Discs for "Offroad"

    The decision has already been made. The dale MT2000 is going Disc Brake. Stuart and I only go off road, and this winter has convinced us that Rims Brakes on very expensive, but Good, wheels do not mix with the grinding paste that is in the mud here in Sussex. The wheels were bought 8 months ago with progressing to Disc's in the future in mind and are Hope Bigun Hubs with Mavic D521 rims. One problem we found last year was that on the longer rides, 100 miles offroad, the brakes were going "off" at around 70 miles. Also the pilots body was suffering, so the extra effort of pulling the "off" brakes on, was almost dangerous. If we had thought of it and changed Blocks,Which we did the following week on a 65 miler, we would have been ok, but what a faff to change when you are tired.

    We do realise about the QR problem with the front Disc involved, so new forks are on the way aswell, with the bolt on hub also being changed on the front wheel. We are going Hope M4's with the largest discs possible both front and rear, So hopefully, you will see us retaining our downhill speed at the end of Rides aswell as the beginning.

    If there is a question to be raised. It is what size disc should we go for on the front and rear of the dale? bearing in mind the restrictions of what can be fitted to the frame. Have any of you carried out this modification? and what are your views on the subject?

  2. #2
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    I just got the standard Magura Gustavs. I use the standard QR on the front without a problem. Avid now makes a cable activated rear in 203cm for tandems. I got one for my road tandem but have not installed it yet.

  3. #3
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    We are using dual Avid 203mm road disc units on our custom Bushnell. Dennis mounts the fork disc on the right hand side, effectively eliminating the quick/unintended release problem.

    Our Al bike has a quite small rear triangle, possibly just that much smaller due to beefy Al tube diameters - Dennis elected to fabricate a mounting plate to accomodate our disk.

    On the form, space is not an issue on our bike.

    I'm going to get around to taking some pictures one of these days...

  4. #4
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    I would go with the smallest size disc that is offered (6"/150mm?). I bike often in the Mountains of N Georgia with long steep downhills and 6" is more than adequate for my Avid cable (vice hydraulic) activated brakes. When discs warm up a little, they get really good and I can't imagine needing more than 6". I can easily lock the front wheel with light pressure from two fingers, especially on hardpack. You save a little weight too.

    Al

  5. #5
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Al.canoe
    I would go with the smallest size disc that is offered (6"/150mm?). I bike often in the Mountains of N Georgia with long steep downhills and 6" is more than adequate for my Avid cable (vice hydraulic) activated brakes.
    Uh, Al... Were you aware that we are talking about disc brakes for tandem bicycles?

    For an off-road tandem that will be used on technical terrain where steep descents will be encountered you want the biggest disc rotors you can fit, front and rear. The larger size rotor isn't needed for increased braking power; instead, the larger rotor is needed for managing the very high heat loads that are generated when you attempt to slow or stop a tandem -- remembering that a tandem is carrying twice as much weight as a personal, one-seat bike. Moreover, the way you use brakes on an off-road tandem is very different from off-road personal bikes. Given the front weight bias on steep descents, it is very easy to lock-up the rear wheel on an off-road tandem which, instead, causes it to be used more as a drag brake with a constant, moderate degree of braking force applied for longer periods of time vs. quick stabs or short hard braking applications. Therefore, the front brake does all the real stopping and, again, remembering this is a tandem that must arrest twice as much weight as a single mountain bike's brake. Both of these braking techniques create 1000's of watts of energy which = gobs of heat. By gobs of heat, I would note we have successfully overheated a rear mounted Hope DH04 brakes w/160mm rotor in the past -- which was the precessor to the Enduro 4 w/185mm that we are running on the back now, aka. the current M4 caliper. The M designation was adopted when they mated the Enduro 4 caliper to their new M lever.

    You should be able to fit a 203mm front disc with the Hope M4. We run this set-up on our Ventana's Stratos S5T fork. We have 135mm rear spacing and run a 185mm rear disc which, at the time we bought this particular tandem, was the largest one the longest reach #8 Hope disc caliper would work with. I don't believe there is a larger M4 caliper available but I could be wrong. Cannondale had originally planned to make the MT available this year with 203mm Avid BB discs front and rear which leads me to believe they have sufficient left chain & seat stay clearance for a rotor size of up to 203mm.

    If you haven't ordered your brakes you might also want to look at the Magura Julie Tandem brake. This has proven to be a sleeper that offers exceptional performance, easy set-up and adjustment, an incredibly long brake pad life for the folks who are using it. Unlike Magura's Gustav M (another, very popular off-road tandem disc brake), the Julie is set-up to run without any drag -- something that some Gustav users just can't get used to. Just something to think about. Oh yeah, and if you have money to burn the Hope Ti6 is pretty awesome too.
    Last edited by livngood; 01-27-04 at 09:17 AM.

  6. #6
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    Magura

    I have Julies on my single- don't waste your money. They are not of equal build quality. My Gustav's have zero drag. I think the drag issue was fixed 2 or 3 years ago.

  7. #7
    hors category TandemGeek's Avatar
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    Quote Originally Posted by Phil from VA
    I have Julies on my single- don't waste your money. They are not of equal build quality. My Gustav's have zero drag. I think the drag issue was fixed 2 or 3 years ago.
    Can't comment on the Julie brakes that came on your single but would otherwise agree that the Julie is clearly not as robust in appearance as the Gustav. However, I've taken a test ride on a tandem fitted with the Julies and was impressed and am otherwise passing along what someone who sells Hope, Grimeca, Magura, Avid and Formula brakes for tandems has observed and received as feedback from satisfied customers who purchased the Julie Tandem and Julie Tandem Plus models for their off-road tandems. Certainly not as definitive as an actual owner's report would be so take it for what it's worth.

    As for the Gustav M's and drag, I'll just paste-in what Magura has on their Web site:

    "Note: with the floating calliper system of a Gustav M a slight drag between rotor and pads is absolutely normal. Correct installation will reduce this to a strict minimum. The Gustav M is by the way the only disc brake on the market for which the manufacturer has given OFFICIALLY green light for tandem use."

    http://www.magura.de/english/bremsen/gustavm.htm

    This is consistent with what I experienced in '99 and what I've seen as recently as two weeks ago on an '03 Ventana being built-up with '03 Gustav's. Floating calipers, they are what they are but they work quite well.

  8. #8
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    I guess what they did was make them self centering a couple years ago. That seems to reduce any drag problem.
    The mountain bike reviews favor the (expensive) Gustav:
    http://www.mtbr.com/reviews/disc_bra.../index_M.shtml

  9. #9
    Time for a change. stapfam's Avatar
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    Deals been done. My local LBS got me the new Hope Mono M4's with 200mm discs front and rear. Front went on a treat, simply bolt on to the Marzocchi's. Rear is causing a bit of problem as A spacer has to be fabricated to get the Caliper aligned correctly. I'm in contact with Hope, and this will be sorted shortly.

    Any one else contemplating fitting parts to a tandem I have only one suggestion. Do not forget to tell the people you are buying the parts from that you have a Tandem, and in my case, the length of spindle in the wheels. That is why I have to get a spacer made.

    [IMG]

  10. #10
    hors category TandemGeek's Avatar
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    Quote Originally Posted by stapfam
    Do not forget to tell the people you are buying the parts from that you have a Tandem, and in my case, the length of spindle in the wheels. That is why I have to get a spacer made.
    Yup. It can ruin your day.

    As in interesting aside, I would note that off-road tandems make short work of the rear spacing myth that suggests "narrow = bad, wide = good". We started off with a C'Dale MT3000 & 140mm rear spacing. No discs mind you, but having been subject to the 145mm vs. 160mm debate I was amused at how durable our 140mm rear wheel was (rim bracing & lateral stiffness, not the hub which we shredded in no time). Fast forward to today, we are now on our second Ventana El Conquistador and both have featured standard MTB rear spacing of 135mm. While we're hardly monsters being under 130kg and, even with the extra-narrow rear flange spacing needed to accommodate the disc rotors, weI've yet to have a rear wheel go out of true without extenuating circumstances, e.g., clipping a sharp rock at 30mph that shredded a sidewall and left a divot in the rim's sidewall. Even in the case of the run-in with the rock, the rim was barely knocked out of true which, while it says something about the strength of a good rim and a proper wheelbuild, also suggests that 135mm rear spacing may not be as inadequate as some have suggested.

    Last comment: Hope's rear brake calipers (at least the one's I've installed on our tandems) seem to take a bit of shimming to dial-in so that the rotor doesn't drag. This may have more to do with having a properly faced and plumb caliper bracket but, regardless, it has made initial rear brake installations something of a trial and error process.

  11. #11
    Just Say No to 26" Wheels
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    2004 Cannondale's standard with Avid disc brakes...

    Quote Originally Posted by stapfam
    Deals been done. My local LBS got me the new Hope Mono M4's with 200mm discs front and rear.


    [IMG]
    You'll enjoy the disc brakes. I just thought that I would mention the Cannondale 2004 Mountain and Road Tandems come standard with the Avid mechanical disc brakes now.

    http://www.cannondale.com/bikes/04/cusa/model-4MT1.html

    http://www.cannondale.com/bikes/04/cusa/model-4RT1.html

    BB

  12. #12
    Time for a change. stapfam's Avatar
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    Just an update, 1st time out on the Hope discs, on a quite aggressive ride today. These brakes work!!!!! The feel of them is so progressive and positive, with no grab, compared to V's, and no rim noises from mud under the pads. Absolutely no locking up of rear wheel on loose scree or mud. The only reservation I could have is with regard to the size of the discs, in that they are so large, they could be prone to damage from accidental knocks. Only time will tell if this reservation is going to prove a problem.

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