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Di2 & Discs

Old 06-18-15, 01:47 PM
  #1  
oldacura
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Di2 & Discs

Still gathering information and opinions on a new tandem build. I have done a search but have not found any objective discussion of:

Mechanical -vs- electronic (Di2) shifters - and - Rim / caliper brakes -vs- hydraulic discs for tandem application.

These technologies are evolving pretty quickly and a comparison that is 5 years old may no longer be valid.

I spoke with Mike at Calfee and he was pretty adamant that mechanical shifters on a modern tandem was like buying a modern supercar with a manual transmission. Di2 was far superior.

He also thought that hydraulic discs were an unnecessary additional cost, weight & complexity.

I realize that Di2 precludes a triple chainring. Mike claimed that fairly widely spaced dual front chainrings and an 11 x 36 or 11 x 40 11 speed cassette was a "better" solution than a triple up front with mechanical shifters.

I'm fairly certain that there are strongly held opinions out there on both sides.

Please enlighten.

Thanks in advance.
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Old 06-18-15, 02:33 PM
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Here ya go for the gearing:
HTML5 Gear Calculator

The top box is Di2 with 30-45 chainrings and an 11-40 cassette.

The bottom box is our current 9-speed triple setup with 26-39-52 chainrings and a 12-34 cassette.

As Mike says, Di2 looks pretty good.
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Old 06-18-15, 02:55 PM
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I think there are good arguments both ways. As I said before I used Di2 for several years and decided to go back to mechanical.
If you run double with 11 x 36 or 11 x 40 the jump between gears are going to be big and I think to use Di2 with that requires derailleur modifications.
If you don't do a lot of hills and depending on how steep they are and how strong you are you could use a cassette that is closer range.
Here are some examples of cassettes and the jumps between gears:

Shimano 10 speed: 12-13-14-15-17-19-21-24-27-30

Sram 11 speed: 11-12-13-15-17-19-22-25-28-32-36

Campy 11 speed:
12,13,14,15,16,17,19,21,23,26,29

I prefer cassettes that start with 12T, I would rather have the 14 and 16T than a 11T. Once we hit 35 MPH I don't feel a need to keeping pedaling. Obviously others will feel differently.

I will admit shifting a triple front can be clunky compared to a double, but for me I think its better than having the larger jumps between gears.
If you are stuck on having Di2, then your only choice is going with a double. I talked with Mike a lot when we bought our Calfee, I think he is trying to sell you what in his mind is the latest greatest thing.
There was a period in time when everybody wanted to change from a chain to Gates belt drive. I never felt the need to do so and now probably can't because our frame was built before what is now the current standard spacing for belt drives, but at the end of the day its not going to matter to me. So I think it come down to this:

If you want the latest technology with flawless shifting, no shift cables and don't mind the larger jumps or can tolerate a narrower range of gears then go double with Di2.

If you want a wide range of gears with smaller jumps and feel mechanical shifting is adequate, then go triple with mechanical shifting.

I don't think there is a right or wrong answer, just what works best for you.

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Old 06-18-15, 04:24 PM
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Originally Posted by Carbonfiberboy View Post
Here ya go for the gearing:
HTML5 Gear Calculator

The top box is Di2 with 30-45 chainrings and an 11-40 cassette.

The bottom box is our current 9-speed triple setup with 26-39-52 chainrings and a 12-34 cassette.

As Mike says, Di2 looks pretty good.
That Di2 actually has good spacing if you treat it kind of like half step gearing, and shift the front chainring along with 4 shifts in the back. That might actually work with Di2, but would be hard to keep track of, and probably wouldn't work well with a tandem. But if you just shift the cassette, the jumps are pretty big.

Perhaps you could switch between the 11-40 and a more normal cassette if there weren't steep climbs on the ride.


Mike Sherman's Gear calculator with these settings. Both the Di2 and the triple give up close spacing above 15 mph to add the really low gears.

The Di2 gearing link. (The popup box just tells you that you can save those settings in a bookmark/favorite.)

Each chainring is a different color.



The 9-speed triple link.



~~~~~~~~~~~~~~

For comparison


Here's a Campagnolo 30-39-52 and 12-29 11 speed. It loses the lowest gears but gains close spacing at higher speeds. However, the Campagnolo triple crank can't go lower than 30.

Campy triple link.

Attached Images
File Type: jpg
30-45 and 11-40.JPG (89.9 KB, 44 views)
File Type: jpg
9 speed triple.jpg (64.3 KB, 41 views)
File Type: jpg
30-39-52 and 12-29.jpg (76.4 KB, 41 views)

Last edited by rm -rf; 06-18-15 at 04:37 PM.
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Old 06-18-15, 04:25 PM
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In my mind the Di2 decision boils down to three factors. All depend on personal choice:

First is cost. Since you are talking about a Calfee I assume cost is not a barrier.

Second, do YOU think you need/want and triple? You and your stoker will be riding the bike (hopefully a lot) so all that really matters is what you will enjoy. If you need/want a triple then Di2 will not meet the requirement, period. Weather you need/want a triple is a personal choice. The best way to make this choice is install a mechanical version of the same wide range double that you would get on your Calfee on your existing tandem and ride it for a while. Can you live with those gears? If so then Di2 is a good option.

The third factor may not mater to a lot of folks but some just don't want to be unplugged. They don't like batteries that need to be recharged. Expensive generator hubs can sometimes be found on bikes to avoid having battery powered lights. Like riding a single speed this is valid choice and has some real advantages.


We need/want a triple and await Shimano expanding thier mountain Di2 line to cheaper alternatives. Until then we enjoy our triple and a car with a fun standard transmission too!
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Old 06-18-15, 05:39 PM
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Perhaps I, for one, don't understand how Di2 works. My understanding was that one pressed the up or down button and the electronics put the bike into the next higher or lower gear, meaning higher or lower in gear-inches. Thus one wouldn't care what was being shifted nor would one have a choice of what shifted. Thus in my Di2 chart in post 2, changing gears in the midrange would involve one shift in both front and back every time one pressed a button.

Is this correct? If so, to you Di2 users, does that work on a tandem? And what do you do when the next change is only 2 or 3 gear inches?

I was quite surprised to see that the Di2 spacing throughout the same gear-inch range was almost identical to what I'm getting with our 9-speed triple.
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Old 06-18-15, 06:27 PM
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We have had both mechanical triple and Di2 on our tandems. I have also had caliper and disc brakes. It is all about where and how your ride in my opinion. For us we will never go back to mechanical or even caliper brakes. We seldom ride for extended periods (days)on flat terrain. If you ride mostly on flat terrain you are probably more sensitive to larger jumps in the sweet spot of 15-20mph. We currently ride an 11-36 50/34 and tend to ride in hilly or mountain terrain and need the low gears. If you have never ridden Di2 you really can't make a judgement or even have an opinion as it is really impressive how well it shifts on a tandem. Battery life is measured in months of riding and is very simple to charge. I don't even take the charger on trips that are ten days of continuous riding or less. There are clear indicators when to charge. There is even a nice digital display available to show gear positions and battery level. We have climbed some classic big climbs with it with out issues. The new hydraulic brakes are the best brakes we have ever used on the tandem with great power and modulation. After they are set up they are very simple even on a coupled travel tandem. It is also rather simple to have a couple of cassettes and chains to reconfigure if you are doing a very flat trip and with tighter ratios and wide range cassette for the mountainous trips. 15 minutes to change setups with quick link chains. I don't think there is a thing I'd change on our current setup. YRMV
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Old 06-18-15, 06:31 PM
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Originally Posted by Carbonfiberboy View Post
Perhaps I, for one, don't understand how Di2 works. My understanding was that one pressed the up or down button and the electronics put the bike into the next higher or lower gear, meaning higher or lower in gear-inches. Thus one wouldn't care what was being shifted nor would one have a choice of what shifted. Thus in my Di2 chart in post 2, changing gears in the midrange would involve one shift in both front and back every time one pressed a button.

Is this correct? If so, to you Di2 users, does that work on a tandem? And what do you do when the next change is only 2 or 3 gear inches?

I was quite surprised to see that the Di2 spacing throughout the same gear-inch range was almost identical to what I'm getting with our 9-speed triple.
Di2 works exactly like mechanical in that each shift lever has two buttons one shifts up the cassette or chainring and the other shifts down. they are not linked for sequential shifting on the road version. The new mountain XTR Di2 can shift sequentially with only one right side shifter. You can program the button to shift more then one gear if you hold it down longer just as you can shift more them one gear with mechanical. the di2 shifts are instantaneous .
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Old 06-18-15, 07:34 PM
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We took delivery of a Landshark with Di2/Shimano hydraulic disc brakes a few months ago. (Second post, I know I am new here). I would echo what akexpress said: test out the expected range of gearing that you would expect from a Di2 double. You don't even have to buy a cassette or anything. You could just not shift into the smaller (or bigger) gears you wouldn't have for a 'typical ride'. We have a compact (50-34) with the ultegra 11-32 cassette. It works out to about the same gearing range as a a standard road triple with an 11-26. The jumps are bigger than with a tighter cassette, but 11 speed does fill in a lot of the gaps.

We have also have a tandem with a triple (9 speed) and TRP mini-Vs. I would not buy a tandem with rim brakes again. Although I can't speak to the quality of other systems (shimano with mechanical and hydraulic, Hy-Rd, Spyre) the shimano R785 road discs are excellent. We have 180 mm freeza rotors front and rear.

The shifting performance of Di2 on the tandem is amazing, which is to say that it is exactly the same as Di2 shifting performance on a single. I would never say that shifting performance of the mechanical shifting tandem is exactly the same as my single with the same components. This has been covered elsewhere, but the mountain bike Di2 gear indicator is a great addition to the tandem. It even has a more exact battery indicator than the 'road' junction box, so you don't have to worry about forgetting to plug in the bike, which I have actually not yet had to do.
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Old 06-18-15, 07:49 PM
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Originally Posted by oldacura View Post

He also thought that hydraulic discs were an unnecessary additional cost, weight & complexity.
A few things to add about the above quote: They aren't that much not expensive than a Di2 setup with other discs, $100 to $200. The total weight of our Landshark is 25.0 lbs, with the hydraulic discs and Di2, which I think is pretty good. Yes, it could get a bit lighter with caliper brakes and mechanical shifting, but then I would be prioritizing a number on the scale ahead of overall performance.

The complexity thing is where I think that it would have some drawbacks. Others have had some issues with a less than optimal rear brake feel (squishy), but I have not found that yet (fingers crossed). I'm sure that I will not enjoy bleeding them when that time comes - or I could just pay my local bike shop to do it for me (kind of like when I really don't want to service my fork on the mountain bike and it has be to done - "I could do it, or I could part with $50"). As of now, I think the braking power and modulation are worth it, others may disagree for completely logical reasons - such as they want to be able to easily work on their bikes without buying new tools and reading the fine print on shimano service manuals.
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Old 06-18-15, 11:38 PM
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TooMany


Nice posts, very nice information and analysis.

Now post a picture of your two tandems in the 'what does your tandem weigh? thread and pictures in the 'pictures of happy tandem couples' thread.


WPH
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Old 06-19-15, 07:26 AM
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Thanks for all the inputs. A bit of background on us: Team age = 115. Weight = 290#. We used to ride "quite a bit" but less miles lately. We've done the Ride The Rockies tour around the Colorado mountains about 4 times. We've ascended & descended almost all the the high mountain passes (12,000+ feet) in the state.

Our bike is a 1998 steel Co-Motion Co-Pilot with couplers. It probably weighs about 45 pounds. We have wide gearing - from 32/34 low (I think) to 54/11 high. This is a 3 x 8 drivetrain. We have had need for the low end - climbing a hill with both standing and seeing the speedo read between 3.4 MPH - 3.8 MPH (this is rare). I also revel when we get to do "tandem time" when we pull past a go-fast single and do the 12 - 11 drop and watch him try to hang on. We have pedaled the bike up to 45 MPH on a downhill.

So maybe this is like comparing a 60's muscle car to a modern Ferrari. If we get a Calfee it will be without couplers & we will keep the Co-Motion for travel.

Please keep your views coming.

Thanks.
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Old 06-19-15, 07:37 AM
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Ok, so here is a followup question. We have a Macchiatto and are wondering about converting only the rear to Di2. We'll keep the front triple. Any thoughts on that?
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Old 06-19-15, 08:09 AM
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Originally Posted by JMarino View Post
Ok, so here is a followup question. We have a Macchiatto and are wondering about converting only the rear to Di2. We'll keep the front triple. Any thoughts on that?
You could do it, but you'll be paying most of the cost of a full setup, and getting less than half the benefit. You'll save on a front derailleur, and one brifter, but you'll still need the same battery, and junction box, and the rear deralleur is the more expensive derailleur.

And the big advantage of Di2 is the awesome front shifting.
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Old 06-19-15, 08:14 AM
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Our coupled Paketa has 10 sp DI2 and I would never go back willingly. (Our old Erickson has mechanical mix of XTR/Ultegra/Durace bits and even when in perfect adjustment doesn't hold a candle to DI2 shift speed and reliability.) We currently have it set up with 50-34 and 11-32, but switch the cassette to 11-36 when traveling to more mountainous terrain. We have the K-edge long cage modified rear derailleur. I will upgrade when the sychronized shifting becomes available (as mentioned above, it is currently only available in the XTR line). I'm intrigued by the idea of hydraulic disks, but can't yet overcome my hesitation regarding the forces on the fork. I mounted a TRP Hy/Rd on the rear recently to give that a try. It is OK, but I'm not wowed like I had hoped. Granted, that is not any indication of how the R785's might perform, and in that regard I would take Akexpress' comments as the best info.
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Old 06-19-15, 08:17 AM
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Originally Posted by akexpress View Post
The new hydraulic brakes are the best brakes we have ever used on the tandem with great power and modulation. After they are set up they are very simple even on a coupled travel tandem.
So AK, how do you manage the hydraulics when you pack the bike? I looked around for quick disconnect hydraulic couplers but found nothing.
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Old 06-19-15, 08:19 AM
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We're going with Dura Ace Di2, and Lightning cranks. I believe that the setup is going to give us the gearing we need.

Our normal setup for Florida is going to be 52/36 front, 11-23 rear, wich will give us enough low gear up for anything around here.

For really hilly terrain, we'll go to a 50/34 front, and 11-32 in the rear. (with the K Edge modification we could go to 36) That will give all the low end we could need even for something like Everest Challenge. And with 11 speed, the spacing really isn't that bad.

Only thing that doesn't cover is a big gear for time trials. On courses with downhill, downwind segments, 52-11 is not big enough. (At Masters Nationals last year, 53-11 wasn't big enough given the downhill sections.) This is where the Lightning crank with interchangeable spiders comes in. We'll go to a 135BCD spider and a 56 tooth chainring for TT's.


With all the current options, including compact cranks, mid compact front chainrings, and 11 speed rear cassettes, I think it's much more practical to cover a wide range of gearing with a double crank setup, than it has been in the past.
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Old 06-19-15, 08:31 AM
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As for hydraulic discs, I think it really depends on how you ride.

We've always used rim brakes, and have never felt the need for anything more. There's no problem with the stopping power of rim brakes. So it's a matter of heat management, and modulation. We descend aggressively, braking only to set up turns, and haven't had problems with overheating the brakes.

We did put a rear mechanical disc on for the descent of Haleakala (because Santana tours made us) I didn't find it to have any better stopping power, or modulation than a dura ace caliper.

In my experience hydraulic brakes on mountain bikes do offer great stopping power and modulation, and I would expect that to carry over to a tandem.

But there are a number of downsides to hydraulic disc brakes: they're harder to work on than caliper brakes, or mechancial discs, the whole setup is likely to add more than a pound to the weight of the bike, there isn't a great answer for packing a coupled tandem with disc brakes, they tend to squeal, they're less aerodynamic, and the weigh more.

For all those reasons we're going with dura ace calipers on our new Calfee. However, I'm sufficiently ambivalent on the issue to hedge my bet, and am having the frame built with a rear disc mount for future flexibility.
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Old 06-19-15, 09:17 AM
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Originally Posted by merlinextraligh View Post
You could do it, but you'll be paying most of the cost of a full setup, and getting less than half the benefit. You'll save on a front derailleur, and one brifter, but you'll still need the same battery, and junction box, and the rear deralleur is the more expensive derailleur.

And the big advantage of Di2 is the awesome front shifting.
I don't see a problem with doing that and I don't see why it is "less than half" the benefit. You will have Di2 shifting on ten or eleven gears and missing it on two. I am not sure if the rear derailleur can handle the range of a triple and may need a longer cage.
IMHO any front double these days shifts extremely well. I have Chorus 11 on my single bike and front shifts every bit as well as Di2 did on my old bike. It just takes slightly more effort with my finger.
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Old 06-19-15, 09:50 AM
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The less than half the benefit is based on the fact that Di2 is a bigger improvement to front shifting than it is to back. Flawless, almost instantaneous, shifting under load, with no trim issue in any gear combination.

And good point about range. Depending on the cassette, and the chainrings you're running, the long cage Ultegra Di2 would likely have enough capacity. Although you might want to go to the K edge modification
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Old 06-19-15, 10:22 AM
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I would have to agree that mechanical front / Di2 rear isn't worth it. Our mechanical rear works pretty well. It is the front that take some finess & timing to do it right. Sounds like Di2 front takes most (if not all) of the skill out of shifting. Like a manual transmission in a car. It takes skill to shift well. Modern dual clutch automatic transmissions shift faster and probably better than the best manual transmission drivers.
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Old 06-19-15, 11:41 AM
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We're in a similar situation as the original poster. We have a 15 year old coupled Comotion with 3 x 9 gearing. As we look around for a new bike, finding good wide ranging gearing is our biggest challenge. We currently have 54-44-28 chainrings, an 11-32 cassette, and the convenience of gear indicators on a shimano flight deck. We live in a hilly area, and do need the range of gearing that we currently have.

My local bike shop is testing out a bike with XTR Di2 shifting front and back. The front has is a stock FSA 52-39-30 standard triple crankset, with the XTR Di2 triple front derailleur. The back has the XTR Di2 rear and the XTR 11-40 cassette. I'll be riding it this afternoon to get an impression of how well it shifts. Some potential issues I'll be considering:

1. The angle of the cage on the front derailleur is clearly not optimal for the large road chainring size. The mechanic at the bike shop says he has gotten it to work fine, as long as you avoid extreme chain angles (in either direction).
2. The FSA crankset is officially rated for 10 speed shifting, not 11. Will that affect shifting under load?
3. The low gear is much lower than I need -- I'd be quite happier with an 11-36 cassette. My bike shop believes that sticking with a Shimano cassette is best, so they haven't wanted to try other brands that offer an 11 speed 11-36.
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Old 06-19-15, 12:46 PM
  #23  
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Originally Posted by tandemraw View Post
We're in a similar situation as the original poster. We have a 15 year old coupled Comotion with 3 x 9 gearing. As we look around for a new bike, finding good wide ranging gearing is our biggest challenge. We currently have 54-44-28 chainrings, an 11-32 cassette, and the convenience of gear indicators on a shimano flight deck. We live in a hilly area, and do need the range of gearing that we currently have.

My local bike shop is testing out a bike with XTR Di2 shifting front and back. The front has is a stock FSA 52-39-30 standard triple crankset, with the XTR Di2 triple front derailleur. The back has the XTR Di2 rear and the XTR 11-40 cassette. I'll be riding it this afternoon to get an impression of how well it shifts. Some potential issues I'll be considering:

1. The angle of the cage on the front derailleur is clearly not optimal for the large road chainring size. The mechanic at the bike shop says he has gotten it to work fine, as long as you avoid extreme chain angles (in either direction).
2. The FSA crankset is officially rated for 10 speed shifting, not 11. Will that affect shifting under load?
3. The low gear is much lower than I need -- I'd be quite happier with an 11-36 cassette. My bike shop believes that sticking with a Shimano cassette is best, so they haven't wanted to try other brands that offer an 11 speed 11-36.
Well heck, if that even sorta works, how about going 48-36-24 in front and 11-28 in back? That gearing looks better than what you have now except for giving up a tiny bit in top end:
HTML5 Gear Calculator

You wouldn't use the smallest 3 cogs in the middle ring nor the largest three in the big ring.
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Old 06-19-15, 01:05 PM
  #24  
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Sounds like tandemraw will be on the cutting (bleeding) edge. I will be very interested to hear how it works.

I spoke to Mel at Tandems East. He clearly has a lot of experience and very strongly held opinions. He agrees that the Di2 shifts very well but as one gets older and is riding steep(er) hills, he's not convinced that the snappy shifting is worth the loss of range. He does not use Di2 on his own bike. I imagine he can choose any combo he wants. However, I think that he is a fan of hydraulic discs. Our phone connection wasn't very good and I'm not sure that I heard all he had to say.
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Old 06-20-15, 12:47 AM
  #25  
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Originally Posted by 2frmMI View Post
So AK, how do you manage the hydraulics when you pack the bike? I looked around for quick disconnect hydraulic couplers but found nothing.
When our new Calfee frame was built we were planning hydraulic from the start so the frame was built with guides that allow the tubing to be turned 90 degrees and it comes out of the guide. I just take the two bolts on each caliper and coil the caliper and tubing up and pack it with the handlebars; It actually makes it easier to fit in the case because now the front bar is completely free of the frame. I knew this would work as we have coupled Ventana mountain tandem and have been doing it this way on it however it has traditional mtn bike style guides that use zip ties. When you put the hydraulic calipers back on you just squeeze the lever and tighten the bolts as they will self center since both pads move evenly.
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