jnbrown

We also have a Pave seatpost. My stoker only complains if we have been riding on bad roads. I think it is certainly better than the our old Santana even with a Thudbuster.
I do mount a rack to the seat post, its a tubus rack and is also attached at the rear dropouts so the seatpost is not taking much of the load.
The only other way to mount a rack would be use the brake mounting bolt or straps around seats stays neither of which i liked.
Next time she complains I will let her decide if she wants us to spend $300 on the Ergon.

oldacura

Though I have never tried Di2, the Luddite in me wants to stay away. A bike is one of the last entirely mechanical machines that I use on a regular basis. As a Mechanical Engineer I appreciate that. I like the convergent evolution of all of the components. That said, the Shimano brifters are very complicated and un-repairable. The Di2 replaces a very complex mechanical device with a switch. I would like to try Di2 without buying (yet).

With regard to brakes: My mountain bike has hydraulic discs. My old bike had direct-pull rim brakes. I'm not certain that the discs are "better". They do add a level of complexity. Our tandem has direct-pull "V" brakes. They have worked very well but they do squeal occasionally. On the normal rides we do, I try to plan very carefully to avoid using the brakes whenever possible. However when we have descended a steep hill with lots of switchbacks, we do have to use the brakes a lot. The rims get hot and sometimes the brakes squeal but they do work. I've heard instances of heavy use of disc brakes where the brakes can fade.

Tandem Cycle Works here in Denver is a Calfee dealer. We haven't been there in a long time but a visit is probably in our near future.

oldacura

Another thing occurred to me. We bought our current bike used and have lived with the geometry that it is. Now that we have the opportunity have a custom made frame, how do we choose the geometry? I know that the stoker compartment in our bike is pretty short & the stoker would like more room. How much is enough? How much is too much?

TeamG

Regarding stoker compartments......check out the Tandem Geek's blog ....very informational.....and call Mel at Tandems East and he can advise frame sizing based on measurements.

The Calfee has 29.5in of rear compartment space second only to CoMotion and or Ericksson....and Calfee can custom build to spec the rear compartment as well

jnbrown

Actually Di2 shifters are more than just a switch. There is a chip that converts the switch input to a protocol. From what I read it is based on CAN bus which is used in cars and is like a network.
I am an electrical engineer and when i first got Di2 I tried to reverse engineer it thinking I would make my own Di2 shifter using Campy shifter bodies. I got to a certain point but then decided it was going to be very hard or impossible to decode the protocol. Its even possible Shimano used encryption. That is why they can sell a brake lever with a switch and chip that cost then a few bucks for several hundred dollars, the profit margin must be huge. I also thought if I did spend the time to try and figure it out I couldn't do much with it without Shimano suing me.

As far as brakes go, our previous tandem had V-brakes. Hated them always screaching and grabby. Now we have caliper brakes and find them to be fine, no desire to have a disc.

twocicle

Fairwheels in Tucson has been hacking Di2 for years. Look them up. Some articles online.

jnbrown

"hacking" means they take parts out of Di2 components and reuse them. This is one example:

Hacking the Heck Out of My Di2 9070 ? Dino Sarti

AFAIK nobody has reverse engineered the Di2 chip.
I think it is possible but would take a lot of time and I have better things to do with my time.

bradcycles

Here is a photo of our almost complete build. We are going down to Calfee tomorrow to take it on its first ride.

mtseymour

Brad: You’ll love your new ride. We have a 2014 Tetra with similar specs to yours. Why did you go with TRP Cross Fork? At some point, we will convert from Reynolds Ouzo Pro to a thru axle fork.

Bryan: Nice to meet you at NWTR Bellingham. Hope you have a speedy recovery. Would like to see you latest build when you’re done.

Oldacura: I think you get the biggest payoff with Di2 on a tandem. The shifting is so fast and precise that it’s much easier to coordinate pedaling with my stoker. There’s also no rubbing (due to automatic alignment of front cage) or grinding from mis-shifts. I use SRAM Red mechanical on my road bike, and don’t feel the need to switch to electronic shifting-it would only be a luxury.

We use Ultegra 11sp Di2 with 50-34 chainrings and 32x11 cassette. At the low end, our 30x32 ratio is the same as a triple with 30x 28. For loaded touring, it’s possible to go with a 34T or 40T cassette. We don’t worry about the high-end because it’s a pleasant problem to spin out at 121 gear inches.


Paul

Goldrush

[QUOTE=mtseymour;17962597

We use Ultegra 11sp Di2 with 50-34 chainrings and 32x11 cassette. At the low end, our 30x32 ratio is the same as a triple with 30x 28. For loaded touring, it’s possible to go with a 34T or 40T cassette. We don’t worry about the high-end because it’s a pleasant problem to spin out at 121 gear inches.


Paul[/QUOTE]

Does this work okay?

Our 2012 Tetra is off to Calfee for the Di2 retrofit. Our local mechanic will rebuild it after Calfee makes the need changes to the frame. We want to run 50/34 chainrings with a 11/32 cassette with the ability to go to a 36 or 40 cassette. Shimano told my mechanic that we need to use XTR front and rear to do the. I prefer Ultegra.

mtseymour

If you prefer Ultegra, one option is the K-Edge long cage mod to allow the 11sp rear derailleur to handle 36T cassette. Alexpress had gone this route. According to Lennard Zinn, it's possible to mix the XTR Di2 with a road shifter (presumably Ultegra). Here's the link to the article:

Technical FAQ: Di2 XTR opens up gear options for road bikes - VeloNews.com

You may want to check with Shimano before you spring for a XTR R derailleur. We decided on the 50/34 and 11/32 combo by climbing a nearby 12% hill on our Co-Motion (with triple crank). We figured that our Calfee with Di2 and double rings should climb virtually any hill in the Pacific Northwest, and like the 50/34 & 11/32 combo. The 36 or 40T might be necessary if you do loaded touring or climb Alpine passes.

Paul

merlinextraligh

We went with the K Edge option which gives you capacity for a 36, or 40. So far it works great, but we haven't put a large cassette on yet.

I'm not so sure about using the XTR FD with an Ultegra rear. I believe there are some people on the forum that have had trouble with that setup, even though Zinn's early report was that it would work.

Also the XTR FD is designed to run with MTB rings, where 44 teeth would be a large MTB ring.

akexpress 

We have been using Ultegra 10 and 11 speed with 11-36 cassettes for a few years now with excellent results but you need the K-edge cage modification. The new 11-40 XTR cassette will also work if you put the K-edge in the high spring tension hole and of course use a longer chain. From all indications XTR DI2 deraillures only work with both front and rear together. Ultegra shifters will work with them but you can't mix the derailleurs. I think Zinn did a correction about his statement. Your mechanic is wrong you do not need XTR nor even want it as it will not handle a 50/34.

Goldrush

Can someone explain the K Edge option. Is this a modification to the Ultegra or a different derailleur? Where can I buy them?

akexpress 

It is a new long cage with a repositioned upper jockey wheel that replaces the cage on an Ultegra or Dura-Ace DI2 rear derailleur. If your frame is at Calfee you can get it direct from them or you can send your derailleur to Ace co (K-edge)in Boise Idaho. Get the latest version of the Ultegra Di2 GS cage version to modify as it is proven to work with 11-40 cassettes but the SS version might not work. The derailleurs are on sale for under 200 all over the place.

tandemraw

For those using the 11 speed Ultregra Di2 with K-edge modification, a few questions:

1. Which crankset are you using? I ask because it seems there aren't many double tandem cranksets available. Especially if you want 110 bcd for the drive side, and 130 bcd for the timing side for a gates belt.
2. Also, which 11-36 cassette have you found to offer the smoothest shifting?

akexpress 

Lightening cranks Santana cassette 11-36 very nice shifting. I bought the cassette before Sram came out with theirs so it might work as well

merlinextraligh

We also went with Lightning. It's light, relatively stiff, and has an interchangeable spider, so you can go 110 or 130 BCD. Problem is it's very expensive.

Another option is to use a regular road triple, and run the timing belt on the driveside replacing the outer chainring on the triple.

Paketa is big on this one side setup.

Mike at Calfee said they can do it, but aren't high on it. While it saves weight, it's a bit of a cobbled together approach.

mtseymour

We also use the Lightning cranks and really like them. The low Q factor is another plus. One minor glitch is that the over-sized external bearings are not compatible with the Calfee eccentric. The cups partially cover the two Allen bolts for adjusting the eccentric. Rather than removing the right side cup to adjust the eccentric, we switched to the Bushnell. We didn't have this problem with the Hollowtech bottom bracket.

The da Vinci may be another option for double crankset because it offer interchangeable spiders in 110 BCD.

merlinextraligh

My understanding is that the Bushnell eccentric is an upgrade over the Calfee anyway.

akexpress 

+1

tandemraw

Is the Bushnell eccentric already compatible with inside Di2 wiring, or does it have to be drilled to accommodate the wire?

mtseymour

Di2 does not require any modification to the eccentric. Since our Calfee frame was configured for Di2, the BB shells are slotted. This makes it possible to fish the Di2 cable through the frame. Once the Di2 is properly connected, the wire can be tucked into the slot and out of the way. I believe that Calfee puts a dab of silicon on the slot to prevent the wire from dropping into the eccentric or the stoker BB.

bradcycles

I think it was the only thru axle fork option that would work with the calfee geometry. Some have also used the whisky fork, but that was out of stock and unavailable when we were having our tandem built up.