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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 03-04-14, 10:05 AM   #1
merlinextraligh
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Converting a Tandem road bike to a TT bike

It's not practical to ship 2 tandems to races, so I want to be able to convert our road tandem to a TT setup in a manner that the aerobars, and the road bars can be swapped out relatively easily.

My plan is to have a whole new front end for the captain, integrated aerobars (Excel has a great deal on 3T aura's right now) TT shifters and brakes, and a dedicate stem.

Swapping the hardwear will be easy, just 3 bolts; top cap, and two stem bolts.

The problem is the cables. Brakes will be easy; I'll use a cable splitter for the rear brake, and just swap brake cables at the cable splitter; and it won't be a big deal to undo and redo the front brake swapping cables and housing.

My question is what to do about the derailleurs. The bike already has cable splitters for the derailleurs, but taking the cables apart at the splitters won't allow the front portion of the cables and housings to come free because the splitter won't pass through the bosses on the down tube, given that the bosses are not slotted, like the brake cable bosses.

My thought is to take out the barrel adjusters screwed into the down tube bosses, and cut a slot in the bosses with a dremel tool or hacksaw. I'm a bit reluctant to permanently alter the frame though.

Another thought is to just undo the cable splitter from the cable where it pinches down with the 2 small allen bolts. The drawbacks here are the cable fraying over time, and having to readjust derailleurs with each swap.

Anybody have a better idea how to manage the cables?
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Old 03-04-14, 10:08 AM   #2
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Also to focus this a bit, I don't want to do just clip on bars for several reasons.

We did do that with a stem mounted Oval Concepts system that worked ok. However it broke, and is no longer manufactured. Regular clip on aerobars don't allow for a low enough position, in part due to the rise of the bars above the handlebars.

With an integrated TT bar, I'll get a lower, more aero position, better aerodynamics from integrated cable routing, will not have to break aero form to shift, and won't have to replace the carbon road bars currently on the bike.
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Old 03-04-14, 11:39 AM   #3
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Maybe Di2 is in your future. Very easy swap just plug and unplug wires into front junction box. Even if you slot the cable guides I still think getting two front setups exactly the same length with cable splitters is going to be very hard and you are going to have to adjust derailleurs every time . I also assume you want to use TT shifters on the aero bars? I think getting those cables exact for two different shift systems will be tough.

Last edited by akexpress; 03-04-14 at 11:50 AM. Reason: added info
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Old 03-04-14, 12:35 PM   #4
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Do a good tidy job on soldering the end of your derailleur cables so they don't fray and don't bother trying to put joiners in them.
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Old 03-04-14, 02:13 PM   #5
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Maybe Di2 is in your future. Very easy swap just plug and unplug wires into front junction box. Even if you slot the cable guides I still think getting two front setups exactly the same length with cable splitters is going to be very hard and you are going to have to adjust derailleurs every time . I also assume you want to use TT shifters on the aero bars? I think getting those cables exact for two different shift systems will be tough.
The TT shifters could be non indexed therefore easy to adjust.
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Old 03-04-14, 02:53 PM   #6
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The TT shifters could be non indexed therefore easy to adjust.
That would make sense. Of course, I just ordered D/A 7900 bar ends because its hard to find 7800's, particularly at a decent price.

The "improvement" on the 7900 is getting rid of friction mode. (allegedly to improve reliability, and shave a few grams).
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Old 03-04-14, 02:56 PM   #7
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Maybe Di2 is in your future. Very easy swap just plug and unplug wires into front junction box. .
I think that really is the ultimate answer.

And Di2 is a really good option for a TT setup, given the options of placing shifting buttons everywhere you want.

Unfortunately, it's not going to happen on this bike, with all the changes (and cost) that would be associated.

But a good reason to go with a Di2 2x11 setup on the next bike.
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Old 03-04-14, 04:05 PM   #8
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......My thought is to take out the barrel adjusters screwed into the down tube bosses, and cut a slot in the bosses with a dremel tool or hacksaw. I'm a bit reluctant to permanently alter the frame though.

Another thought is to just undo the cable splitter from the cable where it pinches down with the 2 small allen bolts. The drawbacks here are the cable fraying over time, and having to readjust derailleurs with each swap.

Anybody have a better idea how to manage the cables?
I understand reluctance to modify the frame but my Speedster came from the factory with no barrel adjusters on the down tube and split cable stops. The only adjustment was provided by in line adjusters. I was surprised and didn't like that setup but it functioned ok. Careful inspection of the Supremo graphic on the current Comotion site shows the same setup. I assumed it was a small cost saving change by CoMotion.

I think the non Di2 setup is to cut the down tube cable stops and install in line adjusters on both the TT and road front end just above the cable stop so that you can get and hold good adjustments for both setups. Cost $50?






Expensive option is new tandem with Di2. cost ??
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Old 03-04-14, 06:44 PM   #9
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Cost $50?




Expensive option is new tandem with Di2. cost ??[/QUOTE]...Priceless...

[Couldn't resist]
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Old 03-05-14, 01:33 AM   #10
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My thought is to take out the barrel adjusters screwed into the down tube bosses, and cut a slot in the bosses with a dremel tool or hacksaw. I'm a bit reluctant to permanently alter the frame though.
This would certainly be my plan. I've done it on one bike before - a hybrid that I built up for my Dad that I also wanted to ride when I was at home. He is using it with flat bars, but I setup some old drop bars with levers and cables that I can switch in for me to do longer rides with. Since the derailleur cable slots weren't slotted, I just did this modification myself. It works very nicely.

If you really don't want to put a slot in your cable slots then if your down tube is round and not too large then you might be able to install Problem Solvers clamp-on cable stops, see here, which are already slotted but are not threaded for barrel adjusters.
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Old 03-06-14, 09:13 AM   #11
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I'm going to go with slotting the cable stops. I'll post some pics when it's done.
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Old 03-25-14, 07:07 AM   #12
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So I went ahead and cut the cable stops, and have the bike setup with the new handle bars. It's still a work in progress at this point.

One glitch is that there's no bottom to the threaded cable stops, so when I took the threaded adjuster out of the stop, there's nothing to stop the cable housing from pulling through. Fortunately, the threads on the cable stops still work, so I'm going to put a set of brass threaded adjusters on each set of cables, and I'll just have to unscrew them on each swap. Upside is I'll have the adjusters their to dial in shifting.

Another glitch is I have the couplers beind the cable guide under the captain's BB, so I'll need to resize the cables so the couplers hit in front of the cable guide.

And I need to cleanup, touchup the cable stops, and cleanup the cable routing.

Here it is in TT form:





Cable stop:



Stoker setup:

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Old 03-25-14, 07:43 AM   #13
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I understand your preference for full aerobars and you're already there, but FWIW it looks to me a -17 degree stem could yield the same or even lower elbow pad height with clip-ons on regular drop bars.
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Old 03-25-14, 08:17 AM   #14
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Sorry to late but had another idea.

Could make a cable stop on a small bracket that clipped in to the old ones. Would avoid cutting.
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Old 03-25-14, 08:19 AM   #15
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I understand your preference for full aerobars and you're already there, but FWIW it looks to me a -17 degree stem could yield the same or even lower elbow pad height with clip-ons on regular drop bars.
This is the third iteration. Regular clip ons sit too high above the road bars.

Second iteration was Oval Concept under bars, which mount to the faceplate of the stem, have the pads even with the road bars, and the extensions under. That worked well, except for the construction was flimsy, they broke, and Oval quit making them.

Current setup is as low as it will go with the current -8 degree stem. And right now its about the right palce for me in trading off power versus aero, although I think I could be a cm or so lower, and flatten the extensions.

I've got an adjustable stem that I'll put on as I spend more time in the TT setup, and dial in the position. That will allow dialing it in finer, and acouple of more inches downward range.
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Old 04-07-14, 06:58 AM   #16
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Worked out ok.

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Old 04-07-14, 08:27 AM   #17
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Big Congrats
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Old 04-07-14, 08:48 AM   #18
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Congratulations

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Old 04-07-14, 12:09 PM   #19
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Awesome twosome!
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Old 04-08-14, 06:04 PM   #20
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Congratulations

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Don't think you could say riding a TT is fun!
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Old 04-08-14, 06:23 PM   #21
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Don't think you could say riding a TT is fun!
Misery loves company......

Congrats on the win!!
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Old 04-08-14, 06:43 PM   #22
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Respect, looking at the front crank assembly, remembering my thoughts when first torquing a right hand drive(75'), my body turned a little right, infinity,but noticeably, wondering if "anyone" feels the difference when going from a left drive to a right drive, actually, I'd like to spend some hours on a left drive to unbend, infinitesimally. ymmv
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Old 05-16-14, 06:54 AM   #23
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SRAM wireless electronic shifting is being tested now at the Tour of California.

It could be very nice for a convertible road/TT tandem.

With no shifter wires, you set up road handlebars with road shifters, and TT bars with TT shifters. Only cables that have to swap are brake cables.

Presumably there would be a pairing issue with the shifters, but I'm betting that it won't be that difficult to pair multiple shifters to the same derailleur. You'd want to be able to do so for multiple sifter positions anyway, the way Shimano allows you to add auxillary shifters to Di2.
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Old 05-16-14, 09:55 AM   #24
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The thought of having a bunch of separate wireless components makes me nervous, but then so did the Shimano electronic shifting until it matured into eTube. Wireless = more batteries, more communication links w/possible interference. On the plus side, install on virtually any bike without frame modification required of any sort.

BTW, we have been running Di2 TT extension shifters on our Zefiro drop bars, plus a 5-port front junction box (up from 3) for a little over a month now. Taking the extensions off is as simple as disconnecting the 2 wires from the junction box and unscrewing the extension mounts from the bars which leaves a clean set of drop bars. Done in maybe a minute if you're quick.

I know this isn't a pure TT bar setup and swapping the base bars for a TT wing bar would mean messing with brake cables, it's just an example of what we have for general use. The TT extensions stay on for cruising rollers and such, then come off when we head to more serious hills. With the extensions on, there are no arm pads getting in the way of the base bar tops, or flip-ups to get in your face when tucking downhill. I chose the "ski" type extensions as these align best with my forearm position on the flat tops on the Zefiro base bar.

The built in forearm pads on these bars are not super cushy, which is why you see some people mounting 3T pads & bars on the top of the Zefiro.

Here's some pics:

Attached Images
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File Type: jpg P1040031 (Large).jpg (92.1 KB, 36 views)
File Type: jpg P1040033 (Large).JPG (89.2 KB, 45 views)

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Old 05-19-14, 07:45 AM   #25
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^ that setup with the extension shifters would work for us.

The only thing you're really giving up with "clipons" (assuming you can get the position dialed in) is the ability to shift without breaking aerodynamic form, and the extra set of di2 shifters solves that.

Just have to convert the whole bike over to Di2.
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