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  1. #1
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    An Unconventional Speedhub: C-Dale MT2000 Tandem

    Cool... cleaning out the hard drive tonight, I found the text w/photo links to this write-up I put together and posted on the now defunct Rohloff Owners Club forums, not quite a year ago. I'm reposting here on MTBR for posterity's sake. This is mainly focused on the Speedhub setup, not the tandem build in its entirety. The build details have changed a bit, but the basics of cramming a Speedhub into this frame have not.


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    Here’s an unconventional Speedhub setup I’d like to share. What’s unusual is that I’ve adapted Rohloff's 135mm hub to fit the 145mm dropout spacing of a Cannondale tandem frame. I’ve written this post as a guide to anybody looking to do the same. And as usual, there’s a little bit of a story to go along with it.


    This bike supposedly was born into a charmed life (you can read more about that here: Celebrity Mountain Tandem on eBay...), but interest waned. After years of neglect, I got my hands on it.


    Jumping ahead to the money shot, here it is today:



    Right off the bat, I regretted the fact that we couldn’t run a Speedhub on this frame. I accepted it, and accepted derailleurs back into my life. Anne became adept at kicking the chain into the granny ring when the bike wouldn’t shift down on a steep climb.

    Besides the 145mm spacing, the Cannondale has very thick 10mm dropouts, so sticking 5mm spacers on each axle would have left me with no threads sticking out.


    Spring came, and I was having a conversation with the guys at Rohloff USA. They suggested I take a look at Speedhubbing this bike again, using a bolt-on hub and their “Long” threaded axle plate. The long plate adds about 8mm of length to the non-drive (disc side) axle.



    I brought my frame into Rohloff’s shop, and we did some experimentation. Things began looking up. I ordered a long threaded axle plate from St. John Cycles, and found a used TS Speedhub already built into a matching tandem wheel from Alex at MTBTandems.com.

    This should be a simple project, right?






    As with any proper Speedhub conversion, I chose to drill out the frame’s cable stops. I’ve documented this process to death over on MTBR ((MkIII) Drilling Out Cable Stops...), but just a reminder to protect your frame against flying aluminum chips, mask the immediate area around the cable stop to protect against the cutting bit digging in, and, as always, wear eye protection.




    I slipped the spacers on to the hub, reoriented my shifter box…


    …and found that the only possible shifter box orientation had the cables exiting STRAIGHT DOWN!
    DOH!


Frustrated at this unforeseen roadblock, I contemplated running with this silly cable routing, versus converting the hub to non-disc and simply running a rear Magura HS33. But I posted a picture and my problem on MTBR for advice (Stumble: MT2000/Speedhub conversion; rear disc v. rim).

BTW, I was pretty much dead set against using Rohloff's Speedbone or an alternate OEM2 configuration, unsure of whether the torque generated by such a heavily-loaded bike might damage the frame.

A couple of MTBR posters lent their two cents, got me thinking out of the box, resulting in this solution:




On a bike with traditional 135mm dropout spacing, there wouldn’t have been room to orient the torque arm **inside** the dropout, as I did here.


This is made possible by the 6mm+ gap between the Speedhub and the frame, filled in with four fender washers.


The next challenge was mounting the disc brake caliper. There’s practically zero clearance between the Speedhub rotor bolts and the inside face of the External Shifter, so shimming the rotor out was out of the question.

To compound the problem, the Cannondale’s disc brake tabs (1999 vintage, pre-ISO) are not flush with the inner face of the dropout, but recessed a few millimeters. This left me with a 12 to 13mm gap to bridge.

A visit to a local metal supplier got me a length of 3/8”x1/2” bar stock, which I drilled with two 6mm holes 51mm apart…


…and cut down into a 9.5mm disc brake spacer.

Note that I could *probably* increase the width of the bar stock to 1/2” and eliminate the additional round spacers you see in this next photo (between my aluminum block and the caliper adapter), but be warned that the rotor bolts arc very near to the black adapter, and I had to lightly shave some material off to prevent interference.




Because the hub is now offset to the drive side, the wheel requires re-dishing to move the rim closer to the non-drive side. I ran the numbers in a spoke calculator, and the tension difference was around 10%. Not bad. Two turns tightening the nipples on the disc side, two loosening turns on the drive side, and my wheel was re-centered, right where I needed it to be.

So this is what the whole package looks like, from behind:



On to the drive side!

Nothing could be done to increase the axle length over here. With the opposite side sandwiching ~6mm worth of spacers, I’ve still got a 4mm gap between the Speedhub’s locknut and the inside face of the dropout. I’m taking a gamble that the frame won’t mind being compressed this much.



With the 145mm dropouts compressed down to about 141mm, this is how much threaded axle is left exposed.




Considering the Cannondale’s derailleur hanger is a steel bracket, I can relocate the washer from its intended location (under the acorn nut) and transfer it to the inside of the dropout, to act as an axle spacer. This reduces the amount the chainstays need to be compressed, and also helps out my disc caliper spacing on the opposite side. The washer is nearly 3mm thick.

For now, I’m undecided if I’ll permanently run it this way.



Those were the big hurdles. Now comes the torque arm.

As seen in earlier photos, the Cannondale frame has a chainstay tab intended for an Aria drum brake, popular with the tandem crowd for its ability to be used as a drag brake. The tab serves as my location to secure the torque arm.

First step was to cut the torque arm down to the third hole from the end.


I don’t recall the exact diameter of this hole, but it matches the outer diameter of the M6 washers Rohloff includes with their various parts, including the fixing bolt that comes with the OEM2 axle plate. It’s also very close to some (non-Rohloff) disc brake spacers I had laying around.

So I shove a stack of three of these into the hole, to create a secure mounting location.

The three washers (plus a washer under the bolt head), a fender washer and nylock nut to hold everything in place, all on a M6 x 30 bolt.





Here’s the torque arm lined up with the mounting tab, washers inserted…
…and everything assembled, as viewed from the back side.




Cable routing is a straight shot through the drilled-out cable stops, along the bottom of the downtube...
…through electrical wire clips bolted to the
bottle cage boss, under the bottom bracket…
…then in tandem along the boom tube and chainstay...

…and finally across the torque arm
mounting tab and into the shifter box.



Last Speedhub-related detail is the chain tensioning. I could have gone with the tried and true Rohloff tensioner, but I opted for YESS Labs’ ETR-B, due to its clean appearance and positive reviews.



This installation presented its own set of challenges, some of which you can read about here: YESS Products ETR-B tensioner product review. I settled on 40x16 gearing mainly to accommodate the chain tensioner, but it’s working out well enough for our needs.




I’m happy to once again be rid of derailleurs!

Although we’ve only taken two rides on it since the conversion, the difference in shifting is immediately noticeable. The derailleurs on the tandem were slow to shift, and adjustment was finicky due to the long cable lengths and frame flex.

The old 7/8 gremlin is as prevalent as ever on a tandem. Where on a solo bike we all learn to sense it, and back off the pedal stroke slightly to let the shift drop, on the tandem, the stoker has no clue what’s up and keeps on hammering (in fact, the shifts are so smooth my wife usually doesn’t notice them).

So twice now, we’ve gotten hung up on rolling hills where we suddenly find ourselves stuck in gear 14, quickly stalled to a complete stop. I’ve got to learn to forcefully counter-rotate the pedals, against my wife’s cadence, to allow the shift. I don’t think there’s anything I verbal I can spit out fast enough so she’ll know what’s up, before we lose too much momentum. She’ll have to put up with me “kicking back” until we figure something else out.

And I assume you’re dying to know what it weighs. 50.8 pounds according to the hanging scale, and that’s not including the black pouch with pump, tools & tubes you see strapped under the stoker compartment (pretty much a permanent accessory). I have yet to install a Hopey steering damper up front, and a rear Magura HS33 for the stoker to squeeze as a “just in case” / “I don’t want to go this fast” brake, so I’m planning on another two pounds.


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Since writing this up, I've installed the rear Magura HS33 at the stoker's position that I talked about, and we've had a few more than the two rides I referenced in the post. We documented one with a photo-post here: Tandem Ride Report: Grinding the Flume..., which I posted here in the Tandem forum last July.

I don't recall if I posted the following photo here, but this is the bike something close to its current configuration (in road-mode with flower power slicks), sporting the Maguras, dual Thudbusters, and 220mm rotors (more about those here: Formula 220mm rotor for Tandem?).


Last edited by Speedub.Nate; 05-28-2009 at 04:59 PM. Reason: formatting
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  • #2
    PMK
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    I followed that topic pretty close back then.

    Are you ready to part with your oem fork yet?

    Also, BTW, I came up with a very simple mod to the ATC fork to make servicing the cartridge super easy and consistent for each service. Give Alex a call and he can see if it may be something you want to accomplish.

    PK

  • #3
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    Quote Originally Posted by PMK
    I followed that topic pretty close back then.

    Are you ready to part with your oem fork yet?

    Also, BTW, I came up with a very simple mod to the ATC fork to make servicing the cartridge super easy and consistent for each service. Give Alex a call and he can see if it may be something you want to accomplish.

    PK
    No, not yet, but thanks for the reminder. I've been 100% wrapped up with the house project I told you about and have been nearly completely detached from my bikes and bike stuff since fall. But it's the right time of the year to get that old Cannondale built up and listed on CL.

    I'm curious about the mod -- how does Alex figure in to it? I've got to tell you, since he posted that Fandango 29"er I've been considering parting with green Monica here. If so, I'd need to convert the ATC over to 29" mode.
    speedub.nate
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  • #4
    PMK
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    Quote Originally Posted by Speedub.Nate

    I'm curious about the mod -- how does Alex figure in to it? I've got to tell you, since he posted that Fandango 29"er I've been considering parting with green Monica here. If so, I'd need to convert the ATC over to 29" mode.
    We were talking suspension one day, next it seemed I was testing the ATC on our Cannondale. The drought we had kind of ended any serious testing until South Florida gets back to its routine afternoon rains with an occasional hurricane.

    Not a bad fork for the tandem, steers as well as a moto, but no where the complexity.

    The ATC is an easy 29 swap, actually everything about that fork was easy except bleeding the damper cartridge. Modified it takes maybe 30 minutes to pull the cartridge from the fork, disassemble, clean, inspect, service and bleed, then reinstall.

    Not sure on the 29 for us yet. We'll give one a test ride on our way through Georgia sometime, hopefully soon. I'm working the summer trip idea with my rear admiral. Take our tandem and hit Tsali, Fontana and a few other spots in that area (Georgia) is what I'm pushing for.

    PK

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    Just as an aside comment, I requested the mods to relocate this to the IGH forum since it's mostly about the Speedhub, less so about the tandem.
    speedub.nate
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  • #6
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    Wow! You've put together so many ideas I've been having. I've been wanting a mountain tandem.

    To make a long story short, I'm stongly considering a Rohloffed Fandango 29er. I really thought we'd need a FS tandem since we ride some rough trails but a recent test run with taking my road tandem off road with 37c tires has me thinking a HT with a Thudbuster or two might be plenty of suspension for us. After leaning towards a HT, I also had the thought of using it as a road tandem as well.

    Anyway, since you've already got some real world experience with yours, I was wondering what your thoughts were. What are the strengths and weaknesses of your current set-up? How would you build up a brand new tandem?

  • #7
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    Your wishlist sounds similar to mine: 29"er, Speedhub. Starting out, I ended up with neither. I'll live with 26" wheels for a while if need be, but hooking up a Rohloff was a huge jump in our riding enjoyment! But I think it's only a matter of time until I get ahold of a Fandango.

    Strengths and weaknesses are impossible to evaluate seeing as this is the only tandem we're riding. I read that the Cannondales with suspension forks are dogs, and yep, the steering feels pretty slow on this bike. But I've got nothing to compare it to other than the rental tandems we've taken out in the past, and those weren't really off-road worthy. I suppose my biggest lesson learned is to choose frame size wisely, and from there, proceed carefully, to avoid unnecessary expenses.

    Definitely spend some time in the tandem forum here, and considering joining the Double Forte group on Yahoo! to absorb some of the great experience.
    speedub.nate
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  • #8
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    Know what? Let me add to that...

    Good brakes and good shifting are a must. We started out with problematic shifting and mediocre brakes, both of which greatly detracted from our experience.

    I'm not sure I ever would have been happy with derailleurs. The current brake setup is doing great, even on the crazy steep stuff.
    speedub.nate
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  • #9
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    Fantastic job
    and great post

    Thanks!!

    Fabricating a road tandem now thanks :-)
    www,chernibikes.com

    HAND CRAFTED RIDING MACHINES @ Face Book
    Chernichovsky Bicycle Labs

  • #10
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    Happy to know this old, dusty post is providing info and/or inspiration. You Speedhubbing your beast?
    speedub.nate
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