act0fgod

So I didn't grow up with bikes and don't fully understand gearing ratios and such. What I do know is we took our coupled tandem on a vacation via air last week. When we got there and I was setting up the bike I found the little plastic piece broke that's at the rear of the bottom tube where the rear derailleur and rear brake cable run, making shifting impossible. I was able to make the bike ridable by looping the cables around a screw that held the plastic piece in place. We effectively lost quite a few of the gears. Also it's always been tough to get the front 3 gears to shift smoothly. Usually we're stuck with either little/middle or middle/big.

We've been looking at electric for awhile but now we're going to do it.

So trying to decide between sram etap and shimano di2. It looks like the etap system is what I want as it appears to be the easier setup and gets ride of cables all together (since we have a coupled tandem that we like to travel with).

The bike currently has a sram 9 speed rear cassette with a campy derailleur with shimano dura ace index shifters.

Reading online it looks like the sram etap can handle 11-40 rear cassette with a roadlink. Will a standard 11 speed chain need to be modified? I believe that I can buy a shimano 11-40 mountain bike 11 speed cassette that will fit on my current freehub (likely requiring removal of the final spacer on our current setup). On the front I don't know what rings I'll want. Also not sure how difficult it will be to convert the front triple to a double. Is it as easy as taking one of the chainrings off?

When looking at di2 I mentioned the disadvantages of cables. The advantages I see are increased battery life and an auto trim. Also assume we would go with the xtr rear derailleur but it looks like they are compatible with the road shifters.

I'd appreciate any insight or recommendations. Thanks.

fietsbob

OK, this is about electronic shifting , not an electric motor to make the bike go, right?

I have not seen any on tandems ... if you have doubts , stick with cable shifting that you can trouble shoot..

...

Alcanbrad

mtseymour

If your frame doesn't allow for internal cable routing, then eTap is the way to go. If it's easy to modify your frame for internal cabling, then Di2 offers several advantages that you didn't mention:

-Synchro shifting. You use use one shifter to control the front and rear derailleur. The "full" synchro mode eliminates cross-chain and works very well. Auto trim is a plus.
-Visual display. The MT800 shows battery life, gear position, and shift mode (Full, Semi, and Manual). You don't have to ask your stoker about gear position.
-Ultegra Di2 is less expensive than eTap. However, eTap is slightly cheaper than Dura Ace Di2. Ultegra Di2 shifts as well as Dura Ace Di2 and eTap.
-Customization. You can use an iPad to change shift speed, synchro pattern, and gear sweep (2 or 3 gears with one touch).
-Availability. Ultegra Di2 is much more common than eTap so it's easier to find parts and get service. This may be significant if you travel off the beaten path.

If you're going with a 11-40 rear cassette, any 11-sp chain will work if it's the right length.

If you're running a triple crank, removing the granny will provide the right chainline and gear ratio. The eTap or Di2 front derailleur may not reach the big ring. To get the full benefit of electronic shifting, you should switch to a double crankset with 50/34 or 52/36 ratios. Don't exceed the 14T gap between rings because it will compromise shifting.

Unfortunately, your choice of tandem double cranks are limited to da Vinci and Lightning. I'm not a fan of da Vinci because it uses a square taper BB. We're really happy with Lightning cranks but it's more expensive.

With either eTap or Di2, the shifting is far better than a cable-actuated drivetrain. If you can afford it, you won't have any buyer's regret.

Artmo 

I can recommend the SRAM etap Wifli, having recently fitted it to our CoMotion Macchiato.It is very easy to fit and complete instructions are here Once you have the SRAM kit, you will have to convert your triple to a double, decide what gearing you need, change the cassette and add a road link.. Ric and Marcia at House of Tandems in TX (713) 725-6554 can help you with this. In fact they are here at the Georgia Tandem Rally in Athens, GA showing their SRAM setups.
You will love it.
Good luck!

obrentharris 

I do not know of a Campagnolo rear derailleur that will play nicely with Shimano shifters, though I have gotten Shimano 8-speed derailleurs to work very nicely with Campagnolo 10-speed shifters.

Perhaps this is at the root of some of your current shifting problems.
Brent

OneIsAllYouNeed

act0fgod

Based on no internal routing going with etap.

A bit confused with what I should get on the double because you mention a double crankset with 50/34 and 52/36. Do you mean a 16T gap?

My wife is a bit worried about the loss of gearing. I went and counted teeth and we have and we have 11-34 cassette with 28-something-53 on the triple.

I went to Berkshire Sports - Bicycle Gear Ratio Comparison Calculator and found that our low end comes in with some reading of 22 and high end is 127.

If we go 11-40 and 36-52 we loose a bit at the bottom (24) and at the top (125). The top is more of a concern, we honestly couldn't ever get into our smallest gears anyway. Can I just buy a 37 to put on our current middle position and get ride of the small? We have da vinci cranks.

mtseymour

My typo. Chainrings using are usually 16T apart.

Before you remove the granny on your triple, check that the front derailleur clamp will allow the eTap to reach the big ring. The chainline may also be problematic, especially with the tighter 11sp cassette spacing. Since DaVinci offers interchangeable spiders and different BB spindle lengths, they should be able to help with the 2x11 conversion.

You must be a very strong team to worry about the top end! We've ridden with very fast riders (on singles and doubles) and spinning out is the last thing we worry about. We're more concerned about getting dropped on long or steep climbs.

sch

Perhaps 4-5 mo ago an etap setup (R/L brifter, FD, RD two batteries and charger) was ~$1300, but lately prices have drifted up to $16-1700 for same.
By comparison an Ultegra Di2 groupo is about $1200 (includes surplus stuff such as brakeset, singleton crankset, cassette which are of little use on
tandem). Probably do better with individual components for Di2, be a bit more but you get what you want once you figure that out. The display
(eg https://www.bikeinn.com/bike/shimano...E&gclsrc=aw.ds )
is invaluable on a tandem. If you go with etap, be sure to get the WiFli version, which is a longer cage RD, that as is will handle 11-36 cassettes, and with a bit of fiddling or
a wolftooth extender an 11-42 cassette. The Shimano XT Di2 FD will handle a triple, the etap does not. An FD mount angle adjuster may be needed to cant the FD up a little.
Cables can be handled with the dumb 4-way connectors placed at disconnect spots. It is really nice to have access to a full set of cable lengths so as to optimize cable length
to your frame and not have to deal with any extra cables. Shimano XT RD Di2 variant will handle 11-42 stock.

act0fgod

Figured I'd give the update since I've completed the eTap upgrade.

It's not perfect. It's tough to spend nearly 2k and not get perfect but I did have some understanding that it wouldn't be perfect prior to the transition as I'm operating outside the specs.

Cassette is shimano M8000 11-40. I thought I would have to remove the spacer on my hub when switching out the 9 speed cassette but it is built to fit with the spacer in place.
I put a 36T chainring on the inner location of the davinci triple crank, a 52 chainring on the middle then I put a bash guard on the outer position (my wife really likes the bash guard to prevent grease tattoos).
I needed a 120 link chain but can use all gear options due to the wolflink at an angle off my derailleur hanger. It's not tight on the 36-11 but it doesn't flap around and I avoid it anyway.

I love that I can see my current gear position on my garmin. The garmin also gives a battery level.

The problems are:
1) It doesn't shift from gear 8 to 7. Once I shift to 6 it jumps to 6 skipping 7. Micro adjustments will allow the shift to 7 but then it rubs loudly. What I do now is from 8 shift twice and then back once all in quick succession, it works.
2) The shift on the front derailleur 36T -> 54T often takes multiple attempts to change. This is the part that bothers me. I've tried to adjust and it's improved but if I get the shift to always work it ends up rubbing the chain. Maybe someone with more skill (ie any skill) could get it dialed in better than I have. I'm working on it after each ride.

If I were to build a new bike right now I'd probably go with di2. My wife has given me the go ahead to switch the etap to my single and trying di2 to compare. We will see how it works out over the next couple months.