Dean V

Do you climb fastest at 95rpm as well?

Ritterview

If we look at pro riders, they will have a lot of watts/kg, and so don't need the low range gears that a tandem needs. So, they could dispense with gears, and have the jumps of turbotandem's. Do they use 6 speeds cassettes, or go with a single chainring sans FD? No, they use a double and 11-speeds.

Pro cassette from Cycling News:




Apparently, professional cyclists find that 'a narrow range is needed to get optimum performance'. So, the argument is settled by appeal to authority of pro cyclists. For the rear cassette, narrow jumps > wide jumps.


Turbotandem's Di2 setup (top), compared to a typical pro rider set up (bottom).




For a tandem, there are a lot of watts, but many more kg. Lower gears are needed. The question is which is preferable in obtaining the greater range needed on a tandem, (1) sticking to a double, expanding the range of cassette cogs, and accepting the jumps, or (2) obtain the needed range with a third chainring, and thus maintain the narrow jumps of a tight cassette.

It would be nice to have EPS or Di2, no doubt, and that might be reason enough. But if just mechanical shifting, I really don't see what I am giving up with a triple. It shifts just fine. The Lightning triple weighs only about 100 grams more than the double (and the smaller cassette is lighter). Because of the granny I can have both the wide range we need, and the narrow jumps of a professional cyclist.

akexpress 

We now have about 700 miles on our Di2 (Ultegra)on our coupled Calfee. We just finished a Santana tour of New Zealand. It was about 500 miles and about 24,000 ft of ascending. Our setup is a compact 50/34 and 11-36 cassette. We previously had a triple 52/39/30 and varied the cassette from 11-28 to 11-32 depending on the trip. We had climbs on this last trip up to short durations of 20% with lots of extended climbs at 8-12% per Garmin readings. The bike shifts like a well tuned single now and i will never go back to mechanical on a travel tandem. We connect one internal wire at the lower boom during assembly now and never touched the system once. There were 27 tandems on this last trip and 4 DI2 (two Dura-Ace and two Ultegra). With the exception of one Ultegra system that was on a 3 week old bike none of them ever went on to the stand for work. That one did for 3 days until the mechanic pulled the crankset and realized the inner chainring had been put on flipped and therefore the spacing was incorrect. I think almost every other tandem had adjustments done. Most were related to front triple especially going into the small chainring. One team whom are very strong riders have a great system if it doesn't drop, stoker is adept at a unclipping and kicking the derailleur to get it to drop. As this last trip had lots of very steep transitions at the bottom of ravines it did require dropping to the little chainrings under load and the DI2 did it flawlessly. When in a fast tandem paceline on the big ring we never felt the jumps were too large and only did a few double shifts which are very fast and effortless without need for communication. We are not a super strong team but always ride in the front group on these trips and tend to get gapped a bit on long climbs. We can pull our fair share on the flats and rollers. I say this just for reference so maybe you can use it to relate to your needs. I find this forum fascinating because the opinions given are hard to relate to sometimes because there is no reference as to riding ability or fitness. For us the Di2 was worth the expense and basically turned our 5 year old Calfee into a brand new bike with the latest drivetrain.

waynesulak

As a we are not a strong team and on a hour flat time trial we would be happy to average 20 mph. Last year we finished a flat 100k. Right at 20 mph but was able to draft quite a bit. We were very happy as the heat index was about 115 for the ride.

I think gearing is more important for low power teams than for high power teams. We have little margin for error in gearing and must get it right to finish a ride strong. Grunting up a few hills results in suffering to finnish the ride.

To answer another question - yes we like just the right gear when climbing too. Too low a gear and we bog down so if a gear is just a little too high and our cadence drops below 90 then. We downshift. If that took us 15 perc slower we would have to live with that. If it only takes us 8 perc slower then we might be able to go a little faster.

I can see the advantage of Di2 especially on a S&S travel tandem. We like our triple and if they had an electronic triple then we would just have to consider the price and weight. As it is i don 't get that far.

i do differ from Ritterview reference to pro teams. Maybe because we are so much lower power but I tend to think that they ride what they are paid to ride, the newest stuff. I don't think an eleven speed gives the Campy teams an advantage over a 10 speed team. Likewise I don't think. Di2 gives an advantage over a well working mechanical system. The mechanical systems do work well just like the Ad copy used to claim so there is not much room for improvement by going to electronic. I think the pros are more concerned about dropped chains or broken chains both of which I attribute to bad setup maybe by a tired mechanic who spent all Day riding in the team car and most of the night cleaning and adjusting bikes.

Turbotandem

If Ritterview or Waynesulak could put the gearing in terms of cadence I think it would be more clear. What I get is this. At a given speed, let's say 18mph at a cadence of 105, right at the point you want to shift up. On the waynesulak gearing your cadence drops 10 counts to 95 rpm as you shift in to the next higher gear. On a Di2 gearing, like mine, you drop 12 counts to 93rpm. I have trouble believing 2 counts rpm difference is really making or breaking any team's power. Ritterviews charts are unlikely to distinguish 2 points of Rpm. Seems like a lot of analysis leading to the wrong conclusion, that you must have those couple points rpm. If 2rpm really broke the bank, one thing we do is this: 1) shift up, 2) stand into the pedals for a couple strokes, 3) sit and whala you are in your sweet spot cadence. If you can't hold on, it's more likely because the extra mph are just out of reach for your power. We've been there! We love to chase down singles, especially uphill, so we've been thru every scenario when the target single is just a little too good. I've been known to push time trial heart rates in those attempts.

I certainly concur with Akexpress, that our riding is much more fluid with the Di2 and I would never go back. Although I confess I do have the braze-on to the frame as a fall back should Di2 ever fall off the planet. I certainly don't make call-outs for gear changes lest my stoker buck. The shifts are so smooth she most often does not know we have shifted. You're over stating it Ritterview! I certainly advice teams that ask me, that the di2 is fabulous. Front auto-trim not to be overlooked in itself is a great advantage. I did recently learn that the SRAM Red 2013 double front der. apparently swivels as it shift and maybe finally solved the trimming needed on all other FD's. But still, that's a double.

Another factor we considered is that going to a 2x10 drivetrain was requisite in upgrading our tandem to a right side inboard belt. The gains in performance from that Paketa advancement was well worth the change to 2x10, while giving teams the option to go Di2 in the same upgrade. Going from a paketa left side to right side belt, I've measured far in excess of 5% improvement on things like our standard hill climbs every month, but I cut that figure by three and suggest the drivetrain adds 5% to our performance. That is certainly more than the potential reduction in our power when we drop our cadence by 2 more rpm than a tighter geared tandem. So my interst in di2 is compounded when compared to a team considering replacing their current drive train. Still, I'd make that recommendation by sharing my experience with Di2 here.

Turbotandem

Oh, I wanted to share on another point. Getting the internal wiring thru a tandem, especially if you are retrofitting. As far as I know, the wiring can not be done thru the top tube because the seat posts prohibit it. But in the bottom tube the wiring has to get past the front eccentric which fills the whole shell. What was don on my frame, below, is the down tube and captains seat tube kiss each other just barely above the captains BB shell. The join looks to be full of weld, but there is apparently just enough room to get the wire over and across to the bottom tube as well. The wire harness crosses over the shell in that small gap. From here the harness goes up the captain's seat tube to the internal battery in my seat post,and then back down the seat tube to the bottom tube where it crosses to the rear. At the rear BB there is the normal room to get over the BB. Getting past the V2r yoke is another matter, but I don't have a picture of that and that's unique to this builder.

As for tandem internal wiring harnesses itself, I don't know a source. Mine was from Paketa who procured it from Bob Davis or Phil Wood, I forget. They'd got it for a NAHBS project that ended up on my bike. Is Shimano making a tandem wire harness or are people hacking them?

Ritterview

Great, now waynesulak is after me. He differs.

Ah, I had anticipated the pros-ride-what-the-sponsor-wants retort. The pros also have the UCI 6.8 kg weight limit, so that a rider dispensing with all the FD shifting would gain no weight advantage. However, if you were to attend your local crit or road race, and see how completely amateur and unsponsored Cat 1 & 2's were geared with unweighed bikes, it would be the same as the pros. There isn't any road racing bike taking advantage of the weight savings of a single chainring, 11-36 cassette, and a dummy left shifter (try and find an example. It can be seen in cyclocross, and mt bikes, but not road). The range for single chainring 53 with 11-36 is essentially the same as 53-39 double with 11-25. But the Cat 1 would look at this and recoil at the size of the jumps.


Single chainring 53 + 11-36 top, and 53-39, 11-25 bottom.

So, the appeal to the authority of pro racers (and Cat 1's) stands. Jumps matter. If jumps matter for fast-accelerating watt/kg-endowed road racers, then they matter all the more for relatively lumbering tandems. Note that Formula One racing cars have seven speed transmissions , whereas semi-trailers have 18. More intertia wants more gearing.

Yes Di2 and EPS is the bee's knees, moreso on a tandem, and it is positively heaven for a travelling coupled tandem. But that is to conflate the electronic vs. mechanical and double vs. triple issues. Gotta keep them separated. Show me a crisp, reliable and rapid Di2 shift from the 32 to 28 cog, and I'll show you a large jump. Be Di2 ever so wonderful, it makes no sense for this 295 lb team to embrace the large jumps eschewed by wispy and watt-laden Cat 1's.

Ritterview

Well, gear-calucator has several choices (see drop down on screenshot). For this comparison of your shift-like-butter Di2 double and my rheostat 33-speed triple I've chosen ratios. Does this help? I still see that the one on the top has large jumps!



I use the road bike racer authority to get away from the over-analysis. There is a free market, as it were, in gearing for road racing. If the simplicity and weight reduction of a single chainring racing road bike were worth the inefficiency of widely spaced gearing, then it would have been adopted. It has not been, even though that scenario would eliminate the FD, chainring, bolts/spacers and left shifter for much higher relative weight and complexity reduction in comparison to ditching a triple on a tandem. I go to a race, and I see it not. When I see bike racers with single chainring, then I'll start to think about maybe a double on our tandem.

So, I am immune to all this rhapsodizing about Di2 wonderfulness if it comes at the price of a double. As does the Keystone State electorate to their firearms and creed, so too will I cling bitterly to my cables and granny.

Dean V

When we went to a double on the tandem with a 11-34 cassette I was unsure if I could put up with the jumps as we were using a 11-23 or 12-25 with a triple before. What I discovered is the tandem is more suited to a wide range cassette than a single. This is because of the greater speed variations that you get. With a close cassette you are quite often going through 2 or 3 gears at a time so the wider range reduces the amount of shifting which I like. The only time I miss 1 tooth jumps is for flat time trialing where I like to have a 13,14,15 available.

waynesulak

I think we have a different opinion of the change in cadence required by going from a 12-25 cassette to a 11-34 cassette. To put my example in terms of cadence lets look at an example:

We are in the 13 tooth cog under full effort, cadence 100 and the road rises slightly, our cadence drops to 95 so we would like to shift down one gear. On a 12-25 cassette we shift from the 13 to the 14 cog for a change of 1/13 or 7.69%. At the instant of the shift our cadence goes from 95 to 102 (95*1.0769). If we are running a 11-34 cassette then our shift is from the 13 cog to the 15 cog for a change of 2/13 or 15.38%. This is roughly twice the change in cadence at the same speed. The change of 15.38% results in a cadence of 110 (95*1.1538 rounded). For us that difference in instant cadence change 95-102 vs 95-110 makes it difficult. Form my point of view there is twice the increase in cadence 7 rpm vs 15rpm and that is over our tolerance for change. Our comfort level is about 13% change in cadence. More than that is a problem and we really like it lower than 12% when possible. This keeps the cadence range generally 100-90 with some instances of 105 and 85 when the terrain wind speed changes suddenly.

As a side note here it is the percentage change and not the tooth count that matters. A 3 tooth change from 25 to 28 is OK because it is only a 12% change( 3/25) vs a 2 tooth jump in the example above which is a 15.4% change.

Some of the jumps on the 11-34 are similiar to a 12-25 cassette so are OK and if I only used part of the cassette then it might be more workable. My style of gear shifting is to work my way up and down the entire cassette and so I cross chain more than some riders. The terrain we ride has lots of quick steep ups and down with sudden and constant changes in gradient. If we road more engineered roads with constant gradients then the requirements of our gearing would also be different.

Otherwise I am in TOTAL AGREEMENT with what Ritterview said.

joe@vwvortex

To me the thoughts of electronic shifting are very appealing because of the long rear shift cable but as a team we just aren't strong enough to get rid of the gearing a triple affords us. I also like having the tighter gearing in the rear. We started out with a 30/42/54 with a 11-34 9 speed in the rear. From there went down to a 11-32 and a 28 in the front - running Campy 10 shifters. Now we are running a 26/39/53 in front with a 11-29 10 speed campy in the rear. We much prefer the shorter jumps in gearing and maybe it's because we have a fairly high cadence style on the tandem. We have no real problems shifting in the front with a Dura Ace triple fd on FSA team issue CF cranks. Does it take a bit more finesse and planning on a shift to the small ring? Yeah - but I'm so used to it - it's not an issue.

Turbotandem

It's amusing that all manual shift owners love it and do not advocate change. And all di2 owners love di2. It undermines an effective comparison if the banter is simply advocating your own. What is true from the di2 owners is that they all came from manualikes. And not one yet has regretted that change. The manual tandem riders have only charts and numers to refer to and no experience with the two systems to offer a valid expeirince. I go with my experience and not the charts. I would agree di2 is not for touring tandems or teams who are struggling on climbs

waynesulak

Every triple user I know rode a double before riding a triple and switched to a triple because they needed it. I have used an 11-34, and an 11-32 cassette. We are talking about not liking those items not Di2.

Give us an electronic triple then we can compare manual to electronic. The thought of an electronic triple that does everything as advertized would be great. No long cable run issues, great front shifting, what's not to like?

Turbotandem

Wanyenulak in your postin #35 I believe you have a math error by using the cog teeth alone rather than as a denominator in the gear ratio. When calculating cadence the chain ring matters as well and needs to be expressed as gear ratio not just cogset teeth. So were i have an average 11% change in gear ratio and you have an average of 9% change; that's a 2% difference. That is, your cadence changes from, say, 100 to 90 and mine changes 2% more from 100 to 88.
What i actually did was use the gear calculator and set it to include speed; and then slide the cadence bar around to simulate a shift. I think i have that right.

Ritterview

The thing is, we will all grow old before Shimano or Campagnolo makes a triple shifting FD. If you talk to anyone in the bicycle industry about tandems and triples, they recoil from you as does Dracula from a cross.

I think it is doable, however, to modify existing systems to shift a triple. One thing to note is that the 11-speed chains are narrower, and thus the chainrings can be more closely spaced. This requires less range of throw of the FD. There might, even now, be sufficient throw now on Di2 or EPS to shift an 11-speed FD on a more closely spaced triple.

How it could be done for Campagnolo (and presumably Di2 as well) is depicted on this graphic. (1)The new Athena 3X FD donates its cage. (2) If the throw on the EPS FD isn't sufficiently wide, then a longer arm (as depicted) is fabricated using 3-D printing (see video below) to obtain wider throw. (3) The EPS brains are hacked to get it to make 3x shifts. All of these things have been done individually. K-Edge has done more than this to produce a mountain Di2 group.



3-D Printing bicycle parts:

akexpress 

I don't think a electronic triple is happening. at not least from Shimano. About a year ago Bill McCready from Santana had been told it was in the works. Santana seems to have a good working relationship with Shimano and is in the know to some degree. A couple of weeks ago he told me that Shimano is not making and doesn't plan on a triple despite numerous requests. Your feelings regarding Bill aside he has had influence with Shimano in the past and was one of the first to display Di2 on a tandem and has embraced the technology,

zonatandem

Turbo #37 reply:
Apparently you missed our earlier posting. We went from triple to testing Di-2 on our tandem.
Great for about 1,400 miles. Wonderful instantaneous/crisp shifting; loved the automatic FD/chain alignment.
No real issues with going from triple to double chain rings.
Did not love the fact that idiot warning lights did not give warning that it was time to re-charge battery; however FD quit . . . so knew it was time to re-charge.
About 300 miles later tandem quit shifting completely. Battery connector issue + FD would not adjust via the adjusting screws.
All this happened while climbing a hill, which we ended up walking.
Went back to triple with 9-speed bar end shifters.
Reliability is important; we feel electronic shifting is still in its infancy.
Next will be we wireless electronic shifting. Just like what happened with our cyclometers back when we started in 1975 to wired computers to wireless 'puters.
Happy we tried Di-2; glad to have the more reliable mechanical shifting/triple back on our tandem.
Just our input.
Pedal on TWOgether!
Rudy and Kay/zonatandem

waynesulak

Given the chain ring and wheel size are constants I often use the cog size change to estimate the change in cadence. I have found it a very handy shortcut if not exactly accurate. The change is the beginning cadence denominator at various speeds causes small variations in a gear calculator's results depending on the beginning speed chosen while the cog method ignores this small effect. The example below uses 20mph. If you look at the 15 mph column in the graphic the results support the same conclusion but are altered slightly due do the different starting cadence.

See graphic below for internet gear calculator:

At 20mph with a 13 tooth cog and a 36 tooth chain ring the cadence in shown as 92. Moving from the 13 tooth cog to the 15 tooth cog we get a cadence of 107. Diff in cadence is 15 or increase of 16.3% (15/92).

At 20mph with a 13 tooth cog and a 36 tooth chain ring the cadence in shown as 92. Moving from the 13 tooth cog to the 14 tooth cog we get a cadence of 99. Diff in cadence is 7 or increase of 7.6% (7/92).

7.6% vs. 16.3% is more than double the percentage increase. My prior posting #35 mentioned a change of 7.69% and 15.38% so it actual is slightly less of a difference than the web site gear calculator.



Numbers aside, well before Di2 came along the vast majority of tandem riders have decided a triple served their needs better than a double with a wide range cassette and was worth some level of additional shifting hassle. We fall into that category and Di2 is not practical for us as long as it will only handle a double. For those tandem teams than are happy with a double then Di2 or Campy’s electronic system are options to be considered. I suggest that those that like a Di2 double system may also have viewed a double manual system with the same gearing as a small improvement over a triple. The problem with Shimano’s inability to downshift the to the granny under load would have been avoided and shifting improved.

The possibility of a major brand electronic triple is appealing. Triples are a small market to begin with and the high price point of electronic systems further reduces any potential market so I don't see it happening in the foreseeable future. Possibly a boutique builder will put one out and do the needed software and hardware modifications.

I would like an electronic system to allow for shifting from aerobars or from the tops or both!

While I do have a substantial bike budget I think I will spend my thousands first on pedal power meters before electronic shifting.

joe@vwvortex

We don't "struggle" on climbs necessarily - but then again we ride because we enjoy it and not because we have to post our times on Strava. It's also called being realistic and the amount of long steep climbs that we encounter where we ride dictate having gears that don't require us grinding ourselves to death. I've been building and riding road bikes for the better part of 42 years - I've seen it all. I'm happy to embrace advances in technology. However - if it doesn't make sense for a particular circumstance - it simply doesn't make sense.

akexpress 

The best part of all of this is that one has a choice Mechanical or electronic they both work and allow us to enjoy our tandems and time with our stokers!!!!!!

DubT

I have no idea how old you are but one of the things that I have learned in my short 70 years is that once a person has spent their hard earned money on something, then in their mind it is the best and it will remain so until something or somebody comes along to change their minds. That is one reason companies spend billions on marketing.

Our tandem is mechanical, Ultegra 6700 brifters, DA 7803 series FD and Rd, new Ultegra cranks, SRAM 11-28 cassette, and it shifts good. I can always get the triple to shift and if the rear needs to be adjusted I know how to adjust it. The parts are available, prices are decent and I can work on the complete system. Have you gone to the Shimano tech site and looked at the tech manual for electronic shifting? At this time we will stick with mechanical shifting. I believe that in the next 2-3 years I might change my mind but for now we will stay mechanical. I like close ratios, in my racing days I always ran a straight block rear freewheel/cassette. If you are going to stay with the pack you have to have the right gear.

We rarely shift off of the big ring here on the prairie, I use all ten cogs on the rear with the 52 on the front and the FD does not rub. We rarely use the middle ring and even use the small ring less frequently, but when we need it we have it. I am not willing to go wide ratio and give up the triple. If there was a way to simplify the system and use just electronic in the rear I might be more inclined to try it.

Rudy's experience has caused me to decide to wait and see!

Wayne in Illinois

Turbotandem

I did see your entry, and appreciated that you shared the gearing was not the issue, but that the battery died. I understand when the battery is low shimano opted for programming that disables the less critical FD in order to keep the RD running longer. We've not had battery issues after the initial start up period. And it would be nice if there was a true battery life indicator: I don't think they're made since the new batteries are designed to hold a strong level sharge for a long time, and then die sharply. There is no warning. We charge our battery every quarter or so.

Turbotandem

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, https://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.

PMK

Your comparison to MTB riders does support your choice. Where we live it is for the most part flat. Unfortunately we don't have the means to do a lot of climbing and then descents.

We ride both road and off-road tandems. The road tandem is a pretty tight spaced 12/25, while the mountain tandem is 11/34. Trail hopping and on some of the hard pack double track roads, the MTB tandem lets you feel the gearing jumps. These jumps are more noticeable, since we do ride a tighter spaced road tandem.

Not saying wide jumps don't work, just seems that on road, on the flats, tight spacing easily finds the sweetest rpm to turn.

With the flats often providing long runs in one gear, not sure electric shifting would be a plus.

Our luck, we would get caught in an intense thunderstorm, have lightning strike nearby and end any shifting at all.

PK

waynesulak

We ride in the 36 x 13, 36 x 14, and 36 x15 a lot of the time. Just because those gears don't support your case or because you don't ride them seems to make them "extreme". I want a cassette with no large jumps while it appears that you are OK with a mixture of wide and narrower jumps. I don't think my requirement is extreme but if it is then I am OK with that.

Your logic and the use of the word "confronted" implies to me that you are starting with the desire to run Di2 and confronted with lack of triple use a wide range double and say it is just as good. We triple users start with the gearing we want and then use the system available to accomplish that gearing.

I don't see why anyone should give up the gearing they like and convert to a wide range double just to have Di2. If I wanted that gearing I would have been using it on a manual system. Now if they like a double then sure go with Di2 (or Campy - Shimano is not the only system).