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Di2 on the tandem

Old 03-14-13, 12:37 PM
  #51  
Dean V
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Originally Posted by Turbotandem View Post
I see that; when in the small 36t ring and high in the cogset going fast in small cogs the difference in cadence is highlighted. I was evaluating what I see as our normal riding gears, not the extremes. I wish I knew how to post a web image. Since I can, I can only implore readers to consider this cadence site, http://www.machars.net/bikecalc.htm and enter my gearing; what I see is that at speeds in the teens while riding in the 36t my shifts are a change in cadence btwn 10 and 12 rpm. However, I would suggest that we are more often in the 36t when climbing and therefore run at cadences of 75-85 so the steps again come down to 10rpm. And when riding at speeds in the 20's while in the 52t ring, the shifts are a change in cadence of consistently 10 rpm. All well within a ridable range, for us.

When confronted with the unlikely avaialbility of a triple di2, it seems worth evaluating if a cadence range of 10 is worth the gains of Di2 in a deep 2x10 configuration. It was a no brainer for me. And I am not saying it is for everyone, but the positions on the forum suggest the configuration should not even be on the table for consideration. Since the recent advent of the 11-36 light weight casette, it has opened up the potential for tandem di2 for a wide swath of riders. Ritterview's comparison of pro bikes might be more accurate to compare to pro mountain bikes where the range of speeds, including climbing, more closeley resemble tandeming range of speeds. On those pro mtn bikes wide range casettes are well suited as I suggest they are for tandeming.

I acknowledge that if you need more than 24" of gear for your climbs, triples are the only way to go. We sure don't grind to death at 24" of develpment until we get over 15% grades which is not often. Or if you need steps of 5 or 6 rpm.
Unfortunately your choice of bike and componentry is rather a bad one. Until the battery goes flat and you can't shift at all, you will be forever struggling to get the right cadence due to being one short in the chainring department.
As if that isn't bad enough your unrepairable frame will soon either crack, corrode, or maybe go up in flames.
On the bright side, this will at least give you the opportunity to make the correct decision and by a Calfee with a triple crankset. In fact maybe you could make a custom quadruple crankset and use a 11-20 straight block cassette.
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Old 03-14-13, 01:01 PM
  #52  
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Originally Posted by Dean V View Post
Unfortunately your choice of bike and componentry is rather a bad one. Until the battery goes flat and you can't shift at all, you will be forever struggling to get the right cadence due to being one short in the chainring department.
As if that isn't bad enough your unrepairable frame will soon either crack, corrode, or maybe go up in flames.
On the bright side, this will at least give you the opportunity to make the correct decision and by a Calfee with a triple crankset. In fact maybe you could make a custom quadruple crankset and use a 11-20 straight block cassette.
Yeah I guess we are now beating the ground where the dead horse used to be. We have all stated our case. Hope everyone has a great time riding whatever you like.

Last edited by waynesulak; 03-14-13 at 01:22 PM.
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Old 03-14-13, 01:14 PM
  #53  
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Originally Posted by Dean V View Post
Unfortunately your choice of bike and componentry is rather a bad one. Until the battery goes flat and you can't shift at all, you will be forever struggling to get the right cadence due to being one short in the chainring department.
As if that isn't bad enough your unrepairable frame will soon either crack, corrode, or maybe go up in flames.
On the bright side, this will at least give you the opportunity to make the correct decision and by a Calfee with a triple crankset. In fact maybe you could make a custom quadruple crankset and use a 11-20 straight block cassette.
I like it!!! Of course we ride a DI2 Calfee but it is carbon so it is subject to catastrophic failure from any trauma, especially from falling over on a climb because we don't have a little chainring. Seriously I would love to ride with Turbotandem and trade bikes because I don't think you can make a bad choice at these levels of bikes and I would really like to compare the two rides. Of course this is all in fun as we can all agree to disagree!!
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Old 03-14-13, 02:42 PM
  #54  
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Originally Posted by waynesulak View Post
Yeah I guess we are now beating the ground where the dead horse used to be. We have all stated our case. Hope everyone has a great time riding whatever you like.


If it is not dead, it is on life support.

I think this spirited debate has no winner. What works for one team may not work for another. The good news is that we are all out there riding our tandems (hopefully along with our significant other) and we have lots of options.
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Old 03-14-13, 03:48 PM
  #55  
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Thanks Dean V for your thoughtful repsonse. I was dicussing with one of the members off-line why I contribute to discussions on this forum where such a large portion or participants have no interst in exchanging ideas, only in attacking other points of view. As one of those riders out on the leading edge willing to share what I'm experiencing and risk the critisizm for not sticking to the old school; this string rather clinches it that there must be better ways to spend my time fostering the tandem knowledge base than on this forum.
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Old 03-14-13, 04:12 PM
  #56  
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Perhaps it was critisizm, or perhaps a joke that nobody else got. Either way, it didn't seem to contribute much to this thread.

Although our well tuned manual/cable setup is performing great, I do look forward to the day when Di pricing is more reasonable and a more mature product offers a guarantee of no electrical failure. I am also reluctant to give up the range of our triple rings combined with a close-block cassette. Just one missing cog like going from 15-17 in our 11-28 set irks me to no end

Those early adopters out there are forging a path for the rest of us lame-Os who take a lot longer to change up

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Old 03-14-13, 06:02 PM
  #57  
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DeanV - the tongue in cheek response above caught me off guard, mostly because there have been a lot of critical posts as of late (not just on this thread), but I did find some humor in it after it finally dawned on me that it was not serious.

I'll follow on to what Turbotandem alludes to above. I was drawn to the forum as a wealth of knowledge a few years back and there was and continues to be a great deal of insight within our little niche of cycling. I'm all for some healthy banter and spirited discussion, but lately it's risen to a level that has made me choose not to reply to many thread that I would have in the past.

I suppose this is just the evolution of the forum, just not my style. my .02 cents.
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Old 03-14-13, 09:15 PM
  #58  
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I love hearing about the new stuff and technical features.

As for riding the DI2 and your rpm Turbotandem, I asked about your climbing rpm and if you stand while turning those rpm. No reply was posted. I would still like to know, but if not, no big deal.

If it matters, we are horrible standing climbers. Seated we can get to the top when needed.

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Old 03-27-13, 12:42 AM
  #59  
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We climb standing at about 65rpm. On 15% grades or more even slower. Like you say, we can not stand climbing in a fast cadence. But seated climbing, we do work a slower cadence, like 70-85. To that end here is a chart of our cadence in both gears as we progress from 5mph to 40mph with speed across the top of the chart. The spreadsheet has conditional formatting to shade in grey all the gears you can’t use below 45rpm and above 115 rpm. Just to narrow it down a bit further, the spreadsheet has conditional formatting to bold in purple reasonable cadence btwn 85 and 105 in the big rings. And between 65 and 85 in smallest ring as used for climbing.
2x10 chart

3x10 chart


Observations
1) For any speed between 10mph and 36mph, a 2x10 offers a cadence between 88 and 98, as you pick thru the bold cells. That's a cadence range of 10rpm that many here have said is acceptable. When compared to the triple with a 12-28 cassette it produce a range btwn 91 and 100 or steps of 9rpm thru speeds of 10 to 34mph.

2) For any climbing speed btwn 6mph and 15mph I have a cadence available btwn 68 and 76 as picked thru the bold cells; a range of 8rpm. That could be a higher cadence if you elect, I just chose that lower cadence as normal for climbing.

3) As highlighted in a few example speeds in red, for any given speed, when you shift up or down the change in cadence never changes more than 12, most often it’s a change of 10. Only above 26mph do you spin more than 12 cadence change between shifts.

4) If there is anything missing in the 2x10 gearing, besides gears slower than 5mph, it’s for shifts over 26mph. But that drawback is a result of selecting an 11t cog, versus a 12t cog as included in the triple. If we selected the 12-36 SRAM cassette in the 2x12 configuration, the speeds even over 30mph resolve under 10rpm cadence range when shifting
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cadence calculator 2x10.jpg (101.3 KB, 19 views)
File Type: jpg
cadence calculator 3x10.jpg (108.8 KB, 20 views)
File Type: jpg
cadence calculator 2x10.jpg (118.8 KB, 35 views)
File Type: jpg
cadence calculator 3x10.jpg (107.6 KB, 33 views)

Last edited by Turbotandem; 03-27-13 at 01:27 AM. Reason: put highlighter on charts
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Old 03-27-13, 12:53 AM
  #60  
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In the interst of using the forum to share knowledge, for those considering Dura Ace Di2 2013, here are some tid bits on the latest news from a fit up on a new tandem:

2013 DA Di2 has really been spiffed up. Setting it up on a tandem is now a piece of cake, as you can buy the wiring (which is now common to all Di2 including Dura-Ace) in different lengths and just plug it together. In prior years you'd had to assemble a custom wire harness. Shimano also now has their own seat post-mounted battery, so Calfee and Zona batteries are now unnecessary.

If you use an 11 speed cassette then you're stuck with what Shimano offers for the casette and no long cage needed. For deep 10 speed casettes, like an 11-36 SRAM, the Yumeya long cage adaptor was made to work with an earlier-gen XTR rear der which happened to be compatible with the early DA Di2, but it is no longer compatible with 2013 DA Di2. So the only option, unfortunately, means buying an entire Ultegra mech rear derailure just to scavange the long cage which will fit on a DA Di2 2013 rear derailuer.

The 2013 DA Di2 does have ANT+ capability--or so I've been told. Don't know a lot about that. What I have heard is that the digital gear display isn't quite ready for prime time; something about the touch screen not being able to distinguish between a finger and rain or sweat. Shimano's not quite there. And I don't know if Garmin has updated their firmware to read the Di2 ANT+ signal.
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Old 03-27-13, 06:48 AM
  #61  
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Originally Posted by colotandem View Post
I'm all for some healthy banter and spirited discussion, but lately it's risen to a level that has made me choose not to reply to many thread that I would have in the past.

I suppose this is just the evolution of the forum, just not my style. my .02 cents.
I'll make a couple observations, only because I feel somewhat experienced in this area...

1. I've also withdrawn a bit from some of the discussions because as much as I like many of the esoteric aspects of tandems, tandem cycling and bicycle technology I too can find limits to my level of interest.
2. Unlike the forerunner to this forum -- Tandem@Hobbes -- readers are not subjected to EVERY posting via a direct email or compendium of emails, so we do enjoy the ability to "pick and choose" threads that may be of interest, and to otherwise steer clear of topics that aren't for any one of a number of reasons. That is a huge lead forward in technology that does afford us far greater control over the content to which we expose ourselves.
3. Active forum participation can be a challenge for anyone with thin skin or excessive hubris; you're gonna get upset now and again because it's the nature of any mostly opinion-based discussion forum where the absense of tone, body language and traditional barriers to community membership don't exist and, well, "relationships" really aren't relationships. However, being respectful and tactful can go a long way towards bridging those gaps.
4. As "rough" as some of the discussions get here, they're NOTHING compared to almost any non-tandem discussion forum and certainly no where near as contentious as even the Tandem@Hobbes discussions were back in the 90's and early 2000's before membership by most of the passionate folks wanned along with the novelty of internet/email discussion forums.

Just some food for thought. I don't have dog in this fight or any skin in the game... I'm only here because (a) I want to be and (b) can come and go as I please.

--------------------------------------------

P.S. On Topic, although I use primarily Campy and Shimano mechanical systems on our road tandems, I had the opporutnity to demo Di2 for four days on a Santana Beyond back in May of 2011. I shared my observations on the system in a blog entry that you can find HERE.

I'd put Di2 in the same category as most other subjective equipment preferences that tandem owners must make, right up there with brand loyalty, frame material, in phase or out of phase, disc vs. rim brakes, belt vs chain, etc. If you like it and it works well for you, awesome. If you have no interest and like mechanical, equally awesome. It's good to have choices.

Last edited by TandemGeek; 03-27-13 at 07:48 AM.
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Old 03-27-13, 07:37 AM
  #62  
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Originally Posted by TandemGeek View Post
I'll make a couple observations, only because I feel somewhat experienced in this area...

1. I've also withdrawn a bit from some of the discussions because as much as I like many of the esoteric aspects of tandems, tandem cycling and bicycle technology I too can find limits to my level of interest.
2. Unlike the forerunner to this forum -- Tandem@Hobbes -- readers are not subjected to EVERY posting via a direct email or compendium of emails, so we do enjoy the ability to "pick and choose" threads that may be of interest, and to otherwise steer clear of topics that aren't for anyone one of a number of reasons. That is a huge lead forward in technology that does afford us far greater control over the content to which we expose ourselves.
3. Active forum participation can be a challenge for anyone with thin skin or excessive hubris; you're gonna get upset now and again because it's the nature of any mostly opinion-based discussion forum where the absense of tone, body language and traditional barriers to community membership don't exist and, well, "relationships" really aren't relationships. However, being respectful and tactful can go a long way towards bridging those gaps.
4. As "rough" as some of the discussions get here, they're NOTHING compared to almost any non-tandem discussion forum and certainly no where near as contentious as even the Tandem@Hobbes discussions were back in the 90's and early 2000's before membership by most of the passionate folks wanned along with the novelty of internet/email discussion forums.

Just some food for thought. I don't have dog in this fight or any skin in the game... I'm only here because (a) I want to be and (b) can come and go as I please.

--------------------------------------------

P.S. On Topic, although I use primarily Campy and Shimano mechanical systems on our road tandems, I had the opporutnity to demo Di2 for four days on a Santana Beyond back in May of 2011. I shared my observations on the system in a blog entry that you can find HERE.

I'd put Di2 in the same category as most other subjective equipment preferences that tandem owners must make, right up there with brand loyalty, frame material, in phase or out of phase, disc vs. rim brakes, belt vs chain, etc. If you like it and it works well for you, awesome. If you have no interest and like mechanical, equally awesome. It's good to have choices.

As one of the primary participates in the lively discussion in this thread I will add that while Turbotandem and I disagreed on many things I think we both remained respectful of the opposite position and even mentioned in our posts the validity of the opposing position in some situations. Most importantly the discussion remained focused on the subject of the thread and did not become an exchange of personal attacks.

Hopefully the respectful exchange of strongly felt views provides insights to readers of the pros and cons of each position.
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Old 03-27-13, 07:53 AM
  #63  
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Originally Posted by Turbotandem View Post
In the interst of using the forum to share knowledge, for those considering Dura Ace Di2 2013, here are some tid bits on the latest news from a fit up on a new tandem:

2013 DA Di2 has really been spiffed up. Setting it up on a tandem is now a piece of cake, as you can buy the wiring (which is now common to all Di2 including Dura-Ace) in different lengths and just plug it together. In prior years you'd had to assemble a custom wire harness. Shimano also now has their own seat post-mounted battery, so Calfee and Zona batteries are now unnecessary.

If you use an 11 speed cassette then you're stuck with what Shimano offers for the casette and no long cage needed. For deep 10 speed casettes, like an 11-36 SRAM, the Yumeya long cage adaptor was made to work with an earlier-gen XTR rear der which happened to be compatible with the early DA Di2, but it is no longer compatible with 2013 DA Di2. So the only option, unfortunately, means buying an entire Ultegra mech rear derailure just to scavange the long cage which will fit on a DA Di2 2013 rear derailuer.

The 2013 DA Di2 does have ANT+ capability--or so I've been told. Don't know a lot about that. What I have heard is that the digital gear display isn't quite ready for prime time; something about the touch screen not being able to distinguish between a finger and rain or sweat. Shimano's not quite there. And I don't know if Garmin has updated their firmware to read the Di2 ANT+ signal.
Going to a modular plug in wiring system is a great improvement in the Di2 system. One thing both triples and wide range doubles have in common is the need for rear derailleur with more capacity than the standard racing RD. Too bad Shimano doesn't provide for a longer cage RD for Di2 or simply the ability to purchase an after market cage. Here is another place that we are "stuck with what Shimano offers."
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Old 03-31-13, 11:26 PM
  #64  
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I'll post this picture here since we've been having the discussions about drive trains in this thread. Below is the production version of Paketa's proprietary, 69 gram, adaptor. This is hot off the CNC line for mating a right side belt drive 130bcd gates sproket with a 110bcd compact crank, and a 52t and 34t chainrings in our case. At NAHBS 2013 the protoype was revealed as an option for the V2r. I'd previously posted a picture of that prototype in use on our bike, but it was hard to appreciate without removing the crank. And the final version now looks much more refined. It adds a lot of flexibility even if a team didn't want 34t inner ring, the adaptor works for any 110bcd set up, say 54-38, or 52-34 as we have. I don't think any other builders have solved a right side belt, so the details of the adaptor are not something most will need. But is is a beautifully solved bit of engineering, and the machining is sweet. Chaulk up another point for the custom world of high performance tandems where few things are off-the-shelf. Both normal chainring nut and bolts, and 12mm chainring bolts are involved in the assembly. Here, the adaptor is mating a CDC sproket, but it is also designed to propery space with a CDX sprocket. Since the belt for CDC and CDX is the same just with a groove, the front cranks use a CDX sproket to manage the drift of the belt(not pictured)
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Old 04-01-13, 12:09 AM
  #65  
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Originally Posted by Turbotandem View Post
This is hot off the CNC line for mating a right side belt drive 130bcd gates sproket with a 110bcd compact crank, and a 52t and 34t chainrings in our case...
That 52t chainrings are available for 110 BCD chainrings is a development that I missed. It is important that tandem chainrings be stiff for shifting, and a 52t 110 BCD chainring might potentially be less stiff owing to the spider's bolstering ending 20 mm short of the customary 130 BCD.

All the more reason to consider forged Praxis chainrings for this application, due to their reputed stiffness. Praxis makes a 110 BCD 52-36 'mid-compact' chainring set. I don't know if a 34t could be purchased instead to pair with the 52t.

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Old 04-01-13, 12:13 AM
  #66  
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I have considered mounting a Gates ring on a 110 mm crank before, but not actually done it yet. If I did, then I'd start with a Rocket ring, which are apparently now called Origin8, available from Harris Cyclery. They have 110 and 130mm BCD holes drilled on the same extra-wide and stiff single-speed chainring (I have a 46-hole version that I used for a while, which is what made me think of it, they really are solid beasts):


Grind off the teeth and you have a 110 to 130 mm adaptor ring. You may need to play around with extra-long bolts and some spacers to get it in the right place. The rings are only $18 each; I'm betting that Paketa's version costs quite a bit more (although it is more elegant, with chainring nuts and spacers integrated, and unnecessary material already cut away).

As well as being useful for getting good low gearing on single-side drive setups, it could also be useful for people with 110 mm BCD timing crank spiders, like on the Stronglight Impact cranks, who want to run a Gates timing belt.
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Old 04-01-13, 08:49 AM
  #67  
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Originally Posted by Ritterview View Post
All the more reason to consider forged Praxis chainrings for this application, due to their reputed stiffness. Praxis makes a 110 BCD 52-36 'mid-compact' chainring set. I don't know if a 34t could be purchased instead to pair with the 52t.
I do indeed have the Praxis who not only do a good job with ramps and pins, but also designed the compact ring to be more stiff. They are apparently only sold in sets: 50-34 or 52-36. I bought the 52-36 and a 34t SRAM ring figuring the fit of rings / ramps was not that sensitive. This 52-34 is what is in my posted picture. We are Sooo close to being able to use the 36t, but we have some very mountainous double centuries planned as well as a 15,000 foot century with 10% grades throughout and a two mile stretch 14% grade at mile 75: http://ridewithgps.com/routes/2110221. We'll want that 34t ring!

110BCD are avaialble up to 54t, TT style up to 54t which would be quite stiff:
http://www.stronglight.com/stronglig...=plateauclm110
and normal style
http://www.stronglight.com/stronglig...Compact_TYPE_D

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Old 04-01-13, 11:20 AM
  #68  
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Originally Posted by Turbotandem View Post
I do indeed have the Praxis...

110BCD are avaialble up to 56t, both TT style up to 54t which would be quite stiff:
http://www.stronglight.com/stronglig...=plateauclm110
and normal style
http://www.stronglight.com/stronglig..._Zicral_Double
The text reads 110bcd even though the picture is showing a 130
I see. You relate you have Praxis, but in the link demonstrate how up to 56t is available in 110 BCD from Stronglight.
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Old 04-01-13, 12:49 PM
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Originally Posted by Ritterview View Post
I see. You relate you have Praxis, but in the link demonstrate how up to 56t is available in 110 BCD from Stronglight.
I have the praxis.
If one wants more than 52t 110bcd chainring stronglite offers those per the links.

FYI: at 52t x 11 we spin out at 40mph without really spinning crazy, and that's fast enough for me. I am surprised to calculate that with a 54t the same would be true at only 42mph. Not as big a differnce as I had in my head.
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