Gearing - double vs. triple

[tandem_dude]

My name is Doug and I have been a lurker here for the past weeks. I should point out that I am seeing help for it though. :D

I was hoping I could solicit some feedback from everyone. My wife and I have just ordered a new tandem, a Co-Motion Macchiato, built up with Campy Record. This will be our second Co-Motion, fourth road tandem and fifth tandem all around. While we have certainly gained plenty of insight with all of the different tandems that have passed through, it has also created somewhat of a monster here as I look to tweak every bit of the new bike. The most recent change has been to drop the FSA cranks from the build and go with a set of DaVinci cranks instead. (My wife and I top out at maybe 235 lbs as a team, so there is absolutely no concern about going with a standard BB as opposed to one with outboard bearings.)

With that explained, here is the question. Every tandem out there comes with triple cranks. Is anyone running their tandem with a double set up and if so, what has your experience been? We are considering going that route as we believe it will fit our riding style better. I log anywhere from 100-150 miles a week on my single with a low of 39/25 and rarely find myself for want of a lower gear. My wife spends no other time on a bike, but is a runner, so we have similar fitness. In addition, we have similar preference for a higher cadence. While I know climbing on a tandem is nothing like a single (and yes, we certainly use the 22/30 on our MTB tandem), most of the riding we will be doing will be rolling terrain that can easily be handled by a 39/25 if not a 34/25. Thanks in advance for the feedback.

[Fenlason]

We run our newest tandem as a double. Using 55-42. The cassette is an 11-34 10sp. I would change the 11-34 if there was anything in a "tighter 10sp cassette that worked.

glenn

[Fenlason]

Sorry I forgot to say hello and welcome...

Hello Doug.. Welcome to the forum..

glenn

[tandem_dude]

Glenn, thanks for the info and welcome.

Doug

[TandemGeek]

If you were constrained by your components it would be an issue, but if you're going with the daVinci cranks you have all kinds of options... to include same-side drive... and most of them don't lock you in or out of making a configuration change later-on. A long-cage rear derailleur while not ideal for dual drive, also gives you future flexibility if you want to cover your bases.

In other words, because the daVinci cranks use a square spline and bolt-on main drive spider and spider-less cranks you can:

1. Run a standard 110/74 BCD spider for a compact crank configuration
2. Have a second set of chainrings with a granny to reconfigure as a standard triple

You could also decide later on that what you really needed was a 130/74 BCD crankset and obtain a second bolt-on spider with the 130/74 BCD spacing and the right size of chainrings to reconfigure your daVinci cranks. 4-bolts and a slight press-fit on the crank arm's square spline are all that hold the spiders and timing rings on the daVinci crank arms.

Finally, as mentioned, you could also specify that both captain's cranks have the square spline and you could run a 34t timing ring on your right front crank and mount a 34t chainring in the granny ring position on a triple crankset to have a right-side / same side drive configuration with the big and middle ring set up as your dual drive.

Again, lots of options that allow you to change your mind later-on.

While we've always used triple cranksets, the granny ring is rarely used. However, when it's needed it's always nice to have and the weight penalty (75 - 100 grams?) isn't all that bad. We've ridden with a number of teams who have either had doubles or who had on 12x23t or 12x25t cassettes who didn't realize how steep some of the mountains would be in places like North Georgia or Tennessee. Most of them grunted up the hills, where others had to bail. Again, having the daVinci triple mounted to the bike on a 130mm spider doesn't preclude keeping that Alpine chain wheel and bolts/spacers in your tool kit "just in case". The latter is obviously true of other triple cranksets.

[tandem_dude]

...but if you're going with the daVinci cranks you have all kinds of options... to include same-side drive... and most of them don't lock you in or out of making a configuration change later-on.

Having never spent time exploring the daVinci cranks in person (on-line only), combined with the fact that there is no longer a shop around here with anything more than a passing focus on tandems, I wasn't aware of the complete flexibility these cranks had in terms of set up. This certainly reinforces the decision to go with them. Have you ever tried the same side drive set up? Positives? Negatives? Thanks.

[zonatandem]

Welcome to the forum!
Our first tandem in 1975 indeed was a true '10-speed' . . . 2 chainrings, 5 cogs, French Follis.
Perfectly do-able, but then we were only in our early 40s.
However as we age a bit, or get to do some serious long/steep climbs, the value of 3rd chainring becomes apparent. Save them knees . . . got over quarter million miles on 'em and they're still working flawlessly.With the daV crankset it leaves you open to changes/options.
Our take on double vs triple: Better to have it and not need it, than to need and not have it.
Pedal on TWOgether!
Rudy and Kay/zonatandem

[TandemGeek]

Have you ever tried the same side drive set up? Positives? Negatives?

I've ridden tandems with single/same-side drive but, again, all of our tandems use cross-over cranks.

Positives?

1. When building a tandem it allows you to use a pair of standard triple cranks vs. buying a tandem cross-over crankset. This pretty much means you can use any single bike triple cranks that suit your fancy. For example, off-road tandem folks who opt for the Rolhoff hub can use a pair of Shimano XT cranks.

2. It reduces wear and tear on the stoker's bottom bracket by eliminating the torsion loads that run through the spindle which is being pulled forward on the left side of the tandem by the captain's pedal loads, while the right end of the spindle is pulled backwards by the drive train loads.

3. It puts all of the drive train components on the right side of the tandem, leaving the left side "clean".

4. It eliminates one timing ring and a crank spider on conventional timing cranks.

5. It draws lots of attention because maybe one out of 1,000 tandems are set up this way, although this could be a negative to some teams.

Cons:

1. Running a triple with single/same side drive can get tricky and is usually best left to the cross-over crankset.

2. It puts all of the frame bending loads on one side of the frame... probably not a big deal but, heh, it is what it is and some builders make a big deal about boom tube deflection. This configuration just moves it over to the same side of the bike that's already loaded up between the rear axle and bottom bracket on the right side.

3. Dropping your drive train off the middle chain ring into your timing chain get interesting.

4. If you decide you really need a triple or want to run a kid-back you will end up buying a tandem cross-over crankset.

Anyway, that's just some of the things that come to mind.

[Sevenrider]

Welcome Doug.

We are using a double chain ring on our Seven. We have a 55x44 with a 11x25 cassette with Campy Record components including a short cage rear. It is really smooth shifting and I like the close range spacing

We would probably make some changes if we were to ride mountains. So far it has worked well for us riding in Minnesota and Tuscany. It all depends upon the terrain you are riding in and the effort you want to expend for climbing.

[dvs cycles]

We run our newest tandem as a double. Using 55-42. The cassette is an 11-34 10sp. I would change the 11-34 if there was anything in a "tighter 10sp cassette that worked.

glennSRAM makes an 11-26. I don't need the 11 since we are spinners and don't try to set speed records just yet on every downhill so I have a 12-27. Don't know if that is what you meant by tighter?

[regomatic]

Doug,

Welcome to the Tandem Cycling Forum.

We have a triple. We never use the small ring on any of our local rides on the East (flat) side of Orlando, FL. We've used it on almost all the rides we've traveled to.

If you're ever going to have aspirations of riding outside of your flat terrain, go ahead and get set up with the triple. $ & G penalties are relatively low. If you don't get out of town much, and don't plan to, the double may be adequate.

[tandem_dude]

I am so used to a double set up on the road. Purely from a muscle memory perspective, I can drop from the large to small ring while shifting from a larger to smaller cog (or vice-versa) and nail the gearing so the cadence is spot on 95% of the time. It would be nice to keep with that. Agreed about changes to the set-up if we are riding in the mountains, but in that case we might just pull out the MTB tandem and go off road.

Thanks for the perspective on the pros / cons for same side drive. The one that kept sticking in my head would be what would happen if the chain dropped off the middle ring. Could certainly be interesting. Regarding the bottom bracket, I am going to think positive that Phil Wood will deliver something that will hold up with no issues for a light team that prefers to spin.

I am noticing a pattern here that everyone running a double set up is topping in the 55 range. Are you finding that you are coming close to spinning that out? We were actually thinking about going compact to give us more range for climbs. I can't remember the last time I spun the gearing out with a 53/11 and while there is certainly more speed on the downhill with the tandem, we generally find more speed by tucking and letting the bike run.

[tandem_dude]

We have a triple. ... We've used it on almost all the rides we've traveled to.

With the previous Co-Motion, I can think of two times we really took advantage of the triple. Once in Colorado traversing the Continental Divide (not in peak fitness at the time) and on a ride in Northern California where we hit a 22% grade. Other than that, for 99% of our riding we found the middle ring was a little too tall and the inner ring was too low.

Of course now having said that, we'll probably find ourselves wanting a triple more often than not.

[TandemGeek]

I am going to think positive that Phil Wood will deliver something that will hold up with no issues for a light team that prefers to spin.

Having torn-up a somewhat exotic Ti bottom bracket's aluminum end-cap back in '99 due to spindle deflection and being a lightweight team that spins in the mid-80's to mid-90's on the tandem, I've been using steel spindles ever since. In looking at the three Phil BB axle options -- Stainless, Ti, and Super-Duper Ti -- I opted to split the difference and use the stainless for the stoker's BB and the basic Ti model for my BB.

[tandem_dude]

...I opted to split the difference and use the stainless for the stoker's BB and the basic Ti model for my BB.

We are looking at that same set up or just going stainless all around. Still debating that one.

[Fenlason]

SRAM makes an 11-26. I don't need the 11 since we are spinners and don't try to set speed records just yet on every downhill so I have a 12-27. Don't know if that is what you meant by tighter?

Thank you....I very much want the 11... and I am not sure I can handle all the hills in the area all the time in a 26. I almost never need to go lower than our 25.. but I am not sure If I want my lowest to be a 42-26...

glenn

[SDS]

Given that the double and the triple shift with equal reliability and that the high and low of the system are the same, measured in ratio or gear inches, the advantage of the triple over the double is narrower splits between the gears, because the same range is spread over more steps. If it matters to you, you can stay closer to the optimum cadence more often with a triple. If you want to ride with a pack of singles, it makes sense to gear like the singles, so I prefer to use 53-39-28 chainrings, and the smallest cassette I can get away with (11-21 is ideal) for the terrain of the day.

[tandem_dude]

If you want to ride with a pack of singles, it makes sense to gear like the singles...

Which will happen some of the time.

I appreciate all of the various input here. Definitely a LOT of food for thought all around.

[ftsoft]

Depends on where you are riding and your stoker. Personally, I'd stay with the triple. It doesn't cost that much in weight and you need an out gear now and then. We are running a triple with an 11/34 here in the flatlands. Granted, we rarely use the small cog, but we when we need it we really need it (On the Hilly Hundred, for instance). We don't have a lot of long hills here, but there are some short steep climbs that, for us, demand a low gear. We find the gearing on our Co Motion to be a little odd too. We have a 53/39, but I would rather have a 55/42, I think. We mostly run the big ring around here, as we spin the middle ring out most of the time. Good idea about trashing the outboard crank, I went through a set of bearings on my single in less than 10000 miles.

[vtrich]

I'm with Dude. We're in the process of building a new bike,..and I'm wrestling with the same issue. I would like to do the Compact thingy,...mostly for the narrower Q for my stoker. And like you guys, we typically coast and tuck on the longish descents and a 50/14 allows for 25 mph at a reasonable cadence. Of course the whole gearing thing is so personal. I'm sure we all know what we need,..gearing wise,...recognizing some like pushing a big gear up long steep hills,...while others prefer the sit 'n sping thing. More important is the terrain we are not familar with,...and that's where the extra gearing may come in handy. I've gone to France a few times,..and in preparing,..I have thoroughly evaluated the various climbs we were planning on riding,...and they were always harder than I anticipated. Ya'd think 9% is 9% wouldn't you?

GOOD luck and keep us informed.

Rich

[tandem_dude]

I want to thank everyone for their input on this question. It has been a HUGE help. The final decision, and thank you to SDS for pointing out the obvious, was to go with a triple that would be set up the same as my single (53/39) with the addition of an inner ring. Not sure why I couldn't think of that on my own considering the obsessing I am doing over every details, but alas... Still debating what to go with for the inner ring, but we'll sort that eventually.

[ftsoft]

I'm with Dude. We're in the process of building a new bike,..and I'm wrestling with the same issue. I would like to do the Compact thingy,...mostly for the narrower Q for my stoker. And like you guys, we typically coast and tuck on the longish descents and a 50/14 allows for 25 mph at a reasonable cadence. Of course the whole gearing thing is so personal. I'm sure we all know what we need,..gearing wise,...recognizing some like pushing a big gear up long steep hills,...while others prefer the sit 'n sping thing. More important is the terrain we are not familar with,...and that's where the extra gearing may come in handy. I've gone to France a few times,..and in preparing,..I have thoroughly evaluated the various climbs we were planning on riding,...and they were always harder than I anticipated. Ya'd think 9% is 9% wouldn't you?

GOOD luck and keep us informed.

Rich

I ride a compact (50/34) single and I would have some qualms about using that on the tandem. It works for the low end fairly well, but I spin out my 50/12 on some rides around here and I would, for sure, spin that out using the tandem. The 50/11 is another story, but I don't always have that mounted.

Frank

[regomatic]

we typically coast and tuck on the longish descents and a 50/14 allows for 25 mph at a reasonable cadence. Of course the whole gearing thing is so personal. I'm sure we all know what we need,..gearing wise,...recognizing some like pushing a big gear up long steep hills,...while others prefer the sit 'n sping thing. More important is the terrain we are not familar with,...and that's where the extra gearing may come in handy.
Rich


On the few clean descents we've done, we've spun the 53/12 downhill to 34-35'ish MPH or until I start to get yelled at to stop pedalling, then coasted up to 40, and tucked to get about 44.

I'll have to ask permission to get more than that on our next trip downhill on the steeps.

I don't think that's too bad for a couple of "Flatlanders".

[born2pdl]

A triple allows a close ratio cassette! One can always be in the right gear, or in the sweet spot, and that always makes me much happier. With what I call a "tandem compact crankset" (~53/39/28) with an 11-21 or 11-23, you will always have the right gear, be able to do most climbs, and have a good downhill top end. (53/11 is a higher gear than 55/12)

Our good friends run a double. It occasionally limits where they/we can ride.

[aeroboy]

Hello all; I've been lurking around the WWW doing some research for, if all goes as planned, my first tandem purchase in time for the spring. I find this discussion very interesting, as double vs triple cranks is one of the main topics that keeps popping into my head. I'm full of ideas but don't have a grasp on reality, never owning a tandem. By the way, I have my sights set on the Co-Mo Periscope Trident Convertible, 700c, for family transport/recreation as well as racing. We have two kids, aged 3 and 5, and I had thought about a quad, but it is usually only one of us parents at a time that is looking after them and wants to go somewhere or for a ride. If we all travel together, one of us can ride a single. Note to self: will have to ask Co-Motion about the logistics of a Periscope Quad Convertible (to triple or double) ...

Anyways, for one, I have been a bit astounded at the prevalence of triples and high range gearing in general for tandems. Is this because tandems do not climb as well as singles, or is it that tandems are more well-travelled, i.e. get ridden in more locations and more varied terrain, and possibly need to be more versatile than say a road racer?

On my two road machines, one of which weighs ~40lb with its homemade 55W light set, I use a single 52T ring mounted on 165mm track cranks, with 12-21 and 12-23 rear clusters. The chain rarely engages anything bigger than 17T. I find that using the bigger gears up hills makes me go faster, but the hills around here aren't more than a minute or two long. I wonder if lower gears are often used as a crutch when not really necessary. On my racing bike the 52-21 combo is rarely used and I can get up almost anything without going past the 19. For a really hilly road race in '92, Tour de White Rock, I put a 48 on the front.

Based on this, it would seem likely that a double chainset would be sufficient for tandem use, but I'm still not sure. With a 55/42 up front and a 12-27 10-sp cluster, I would have access to far lower gears than with my singles and still have a straight run from 12-17 for hammering, but, and a big but it is, I have to take into account that the wife (strong) will be using it regularly to transport the kids and there could be multiple stokers/captain possibilities. I would love to get into the tandem racing scene, especially TT events.

One aspect of the double vs triple chainring consideration that has not been mentioned is q-factor, which, I would think, will be wider with the triple. This is what I have observed, but most of the triples I see are on cheap MTBs. Are there narrow-q triples out there? I suppose the cranks could be swapped between double and triple as required. For example, especially if entering the tandem in a TT, I might want double cranks on there if I will be stoker, being accustomed to the narrow q factor of track cranks. Are the road triples, Ultegra for example, any wider than the doubles? I've tried to find info on q-factor for various cranks but it is lacking. It's sounding more and more like having a triple back there is a good idea for us, but I still wonder. Would the granny gears be used as a crutch?

I like the idea of a single-side drive configuration. Wouldn't the stress on the boom tube be lower than crossover drive? Cranks rear of the captain's would have their chain tensions cancelled out between the chain that runs forward and the one that runs rearward. The downside of running a sync chain to the small ring of a triple, is that the small rings will generate more chain tension and will wear themselves and the chain faster. In fact, I'm surprised that sync chainrings aren't bigger than they are. Why aren't they, say, 52T? They would cause less stress on drivetrain components and the frame. Has anybody tried/considered this: http://www.bikexprt.com/bicycle/tancrank.htm

Don

[TandemGeek]

Anyways, for one, I have been a bit astounded at the prevalence of triples and high range gearing in general for tandems. Is this because tandems do not climb as well as singles, or is it that tandems are more well-travelled, i.e. get ridden in more locations and more varied terrain, and possibly need to be more versatile than say a road racer?

Let me twist your words a bit and see if this sheds some light on the matter: "I've always been a bit astounded at the prevalence of doubles and low-range / race gearing on bicycles marketed to the average consumer". In other words, tandems tend to come with gearing that is geared to the "average" users needs, noting that the sport riders and racers who make up a small segment of the overall tandem market can readily change the rear cluster to suit their needs. If you'd like to get some insight into tandem teams I'd invite you to visit my survey archive where you'll find several years worth of tandem enthusiast feedback on riding styles, combined age, annual mileage, etc: http://www.thetandemlink.com/surveys/surveycentral.html

I wonder if lower gears are often used as a crutch when not really necessary. ?

Again, you're painting with a very broad brush across a wide range of cyclists, where only a very small number of the teams classify themselves as hammerheads or racers. Interestingly enough, you might find the results from Part I of my 2008 Annual Tandem Owners Survey to be of interest in this regard (Question #9 & others): http://www.opinionpower.com/results.cgi?id=316051829

Are there narrow-q triples out there?

As narrow as you like and constrained only by rear spacing / chainstay clearance, noting that two pair of any cranks can be used for a single-side drive configuration.

I like the idea of a single-side drive configuration. Wouldn't the stress on the boom tube be lower than crossover drive? .... In fact, I'm surprised that sync chainrings aren't bigger than they are.

IMHO, much ado about nothing is made regarding boom tube deflection. Given that the majority of better tandems sold today use sound designs, materials, and methods I personally consider issues like boom tube deflection as primarily a marketing ploy where only a very small number of very large and powerful sprinters who team up on a tandem would really ever need to spend much time trying to address it via frame construction or drivetrain choices on contemporary, well-designed and built tandems. Dubious observations about timing chain slack being an indicator of frame flex seem to conveniently ignore the inherent elasticity of an 80" long chain that manifests itself when the chain goes from slack to full tension during power strokes to something less as captain and stoker's cranks that are in-phase (as most are) move through the top and bottom of the pedal stroke. Interestingly enough, what's not often mentioned is the much larger amount of overall side-to-side frame deflection that takes place at the captain's bottom bracket. The latter can easily be observed by placing a tandem into a wind trainer with the front wheel blocked: it is what it is and it's normal too but nothing that is overly detrimental to the safety or performance of a tandem. Thus, when I hear that someone has "thrown" a timing chain I can usually assume that it's because, a) the timing chain was not properly tensioned and, b) the tandem was likely being thrown side-to-side or hit a bump that set the slack and swinging bottom run of the chain off line enough to be caught by the stoker's crank and/or to derail itself at the rear timing ring instead of excess chain slack created by boom tube deflection.

As for single side drive reducing stress on the boom tube, yes and no. While it eliminates twisting effect on the rear bottom bracket, you still end up with the captain's power going into the sync chain and putting asymetric loads into the boom tube. However, if you really want to mess with your mind, now consider the fact that with single side drive you have now put all of the asymetrical drive train loads on the right side of the tandem: both those between the captain to stoker sync chain axles and those that exist between the rear crank and rear axle on all chain drive bikes. Is that better or worse than having them split up using a crossover crankset? (Rhetorical question here: no reply required)

As for the size of the timing rings, see all of the foregoing. Sync chains and timing rings comprise a simple 1:1, direct drive system. If you want to save wear and tear on the chain and rings, use a higher tooth count but remember, so long as you use odd numbered timing rings or keep your sync chain indexed on even numbered chain rings you can ignore normal wear / replacement indicators and run the same chain and rings until the rings look like saw blades. However, be mindful that the larger the timing ring and the wider the rear spacing is, the wider you're rear crank spindle will need to be. Conversely, a smaller timing ring can be used with a more narrow rear crank spindle can be. You could probably run the numbers on which of the two alternatives -- narrow Q & small rings vs. wider axle & larger rings -- reduces bending forces the most but, again, I really don't think it matters to 99% of the teams who ride contemporary tandems.

In closing, I don't want to come off as a contrarian. However, I hope that my feedback gives you pause to consider the larger tandem market's demographics and how they influence the component specifications used for most production and even many custom frame builds. And, with regard to the drivetrain issues you raised, everything on a tandem involves some sort of a trade off or compromise. There are really no right or wrong ways to configure a tandem -- within reason, that is -- and each team simply needs to figure out what works best for them.

[SDS]

My recollection is that the difference in width between a double and a triple, measured at the pedal holes, is 9mm. Not sure about that, but it isn't a large fraction of the normal 150mm (again, fuzzy recollection) double width. With kids I would get a triple.

I have chased narrow Q in a number of installations over the years, and on drive-side cranksets, the effort is pretty much wasted. The front derailleurs required to get the integrated brake/shift levers to work properly, prefer wide chainring spacing (wider than T.A Cyclotourist cranksets, for example) and a wide gap between the outside ring and the inside of the crankarm. And the chainstays may be wide to match, meaning that it is impossible to use a narrower bottom bracket spindle because that puts the chainrings into the chainstays. The wider dropout spacing of tandems can also cause problems.

The good news is that the front crankset on a tandem, usually does not have a front derailleur or chainstays to contend with, so it is possible to narrow it substantially with appropriate crankset and bottom bracket spindle choices. Again, it seems like a lot of effort to little gain, but if all BB spindle choices cost the same, it doesn't hurt to think about it.

[aeroboy]

TG, even after just a quick glance, the surveys were eye-opening. The people I would likely pair up with in races (my wife and training buddy) are or have been licensed racers, putting them into the elite category, and I am a current Worlds medalist (track). Our own experiences shape our perceptions.

I was under the impression that other than square taper designs, cranks now have a set q-factor - that you can't swap for shorter or longer BB spindles because they are all the same length. This is true on my Cervelo P3 anyway. It has an FSA track crank with an ISIS BB. The track crank has a narrower Q than FSA's ISIS road cranks and they all use 108mm spindles, although it may be possible to get different spindle lengths somewhere else? Is square taper still common with modern tandem cranks? I see that Santana uses Octalink. Do Octalink spindles come in varying widths?

There is so much to learn; there are so many questions. If tandems were more common it would be different because they could be observed on the road and at local bike shops. On single bikes, there are ways to deal with some "issues" that crop up, like chainring-to-chainstay clearance, for example. The chainstays can be longer, or they can be curved so that they exit the BB shell parallel, then curve outward when they are past the chainrings, or even past the crankarms. Longer chainstays would provide more stoker comfort as well. For all I know, long chainstays are common, or it is not commonly done on tandems because detrimental effects on frame stiffness are hard to overcome or unacceptable, or the wheelbase gets too long or some other reason.

Interestingly (or perhaps not) my friend and I never threw a timing chain on his old Freschi. However, we only rode it a handful of times. But we are powerful riders who love to hammer. So I would tend to believe that it is a set-up issue. I have also seen comments about out-of-round timing rings. This could possibly be improved by using track chainrings for the timing, but they tend to use oddball bolt circle diameters. Track chainrings are rounder than road rings, and they are cut deep to hold the chain. They are so good at doing this that I get away without a front derailleur on the road just fine and the chain rarely falls off, chain angle and all. Are timing rings "special" - are they cut this way as well, or are they just road chainrings? I remember a couple of years ago, in the Tour I think, a rider lost the TT because his chain dropped off the single front ring. He was chastised for not using a front derailleur. I've tried this with road cranks/chainrings and yes, the chain falls off at least once per ride, with a single ring up front and no front derailleur.

What it might come down to, is that if using a double crankset allows for a single-side drive and using a triple does not, the double would be hard to resist. I would prefer to run the timing chain on the outside of the drive crank rather than the inside, if it can be done. Is it important that the timing rings be aligned?

...so long as you use odd numbered timing rings or keep your sync chain indexed on even numbered chain rings you can ignore normal wear / replacement indicators and run the same chain and rings until the rings look like saw blades.

So why are odd numbered timing rings preferred? And then even numbered rings? Am I missing something? Are there two types of chainrings in this conversation or one? Sorry, I don't mean to offend but I didn't understand any of it.

[TandemGeek]

I was under the impression that other than square taper designs, cranks now have a set q-factor Is square taper still common with modern tandem cranks? I see that Santana uses Octalink. Do Octalink spindles come in varying widths?

Square taper remains the key to fine-tuning Q-factor to suit preferences (e.g., Phil Wood) and, yes, there are still a few cranks being made for tandems: daVinci are my personal fav's, Middleburn and Specialites TA are the ones that come immediately to mind in regard to tandem crossover cranksets. You can still find some NOS Ultegra tandem cranks as well, but they don't have as many crank arm length options as the daVinci, Middleburn, and Specialites models. The MegaExo (FSA), UltraTorque (Campy), and other overly integrated cranksets do tend to lock you in, but I believe there are a few spindle length options in both ISIS and Octalink. Santana uses a proprietary 70x129mm spindle for their 160mm rear-spaced frames: the 70mm shell allows them to use oversized, round chainstays and the 160mm rear spacing drives the need for a very wide crank axle and special front derailleur mount to move the chainline outboard. Calfee has been able to source the same cranks used by Santana and spec's a 68x118mm Octalink BB for use on their 145 rear spaced tandems and I believe that 68x113mm models may also be available that would work on a triple, noting that I've used both 109mm and 113mm square tapers on Ericksons with the daVinci cranks... but no guarantee here.


Longer chainstays would provide more stoker comfort as well. For all I know, long chainstays are common, or it is not commonly done on tandems because detrimental effects on frame stiffness are hard to overcome or unacceptable, or the wheelbase gets too long or some other reason.

17.0 - 17.5" stays are common on tandems, although we recently spec'd a new tandem with 16.5" stays. Although there are three competing issues on tandem stays: 145mm or 160mm drop-out width, heel clearance, and more recently clearance for 203mm disc rotors. Co-Motion handles this with some very stylish 17" S-shaped stays.

I would prefer to run the timing chain on the outside of the drive crank rather than the inside, if it can be done. Is it important that the timing rings be aligned?

I can't think of a good reason to run the sync chain outboard on a same side drive tandem for a number of reasons, not the least of which is rear chain line. The sync chain's rings don't need to be precisely aligned, but I wouldn't recommend having them too far off-center, i.e., a few mm difference in centerline offset.

So why are odd numbered timing rings preferred? And then even numbered rings? Am I missing something? Are there two types of chainrings in this conversation or one? Sorry, I don't mean to offend but I didn't understand any of it.

Odd aren't preferred, it's just that they wear differently than even number timing rings if the chain remains indexed whenever its removed and replaced. Rather than rambling on, let me offer a link to Sheldon Brown's site where he has an excellent page on tandem sync chains and timing rings that talks to this: http://www.sheldonbrown.com/synchain.html#chainring

[aeroboy]

I can't think of a good reason to run the sync chain outboard on a same side drive tandem for a number of reasons, not the least of which is rear chain line. The sync chain's rings don't need to be precisely aligned, but I wouldn't recommend having them too far off-center, i.e., a few mm difference in centerline offset.


Reasons I was thinking of:

1) An inboard timing chain would probably be limited in size.
2) Addressing the following scenario mentioned earlier in this thread: dropping your drive chain off the middle chain ring and into the timing ring.
3) When breaking a coupled tandem down, or converting a triple to double, I assume the timing chain(s) are removed. This would be much less pleasant an operation (on a single side drive) when the timing chain is running off an inboard ring on the final drive crank.

But then I realized later that an outboard timing ring is going to get more leverage on the BB spindle and bearings, which increases the chance of problems.

It is becoming apparent that a crossover drivetrain may be the best configuration for what I have in mind.

[mrfish]

Following your comments on gearing I was glad to hear you're winning races! You are certainly not the average tandemist.

Do post a picture of the rig you end up with. For your interest and given a picture is worth 1000 words, have a look here. These people in Berlin built themselves a nice single sided rig which uses 135mm spacing and basically mid range road components. Unfortunately only in German, but I can translate if you're interested in any short section. Click on the links where they describe all parts and the first non-working version of the frame etc...

http://www.sudibe.de/renntandem.html

[aeroboy]

Those pictures ... with the rear chainrings it is exactly as I have envisioned! What next? Since my last post, I have still not been able to find 165mm captain's cranks that are also low q factor. Standard road q these days is about 147mm which I could live with. The da Vinci ones are advertised at 158mm which is high for a road double and even a little high for a triple. And they are designed to use a short axle, which minimizes the possibility of the user puttiong a shorter axle in there to reduce q a meanigful amount. The single side config would bypass all of this; I'd love to know where they got the extra long chainring bolts needed to do that. Yes, that's all I need to make it work! Thank you!

[aeroboy]

Don't you worry. If the rig ever gets built - that is, if the builder puts up with my silly little requests, then I will proudly post pictures here. Actually, there is only one feature the frame would need, and I'm not sure if this one has it. At least I can't tell from the pictures. Are the chainstays bent?

Have they described how they got the extra long chainring bolts required to do that, and also what kind of cranks those are? The big timing rings look about right, too.

[TandemGeek]

also what kind of cranks those are? The big timing rings look about right, too.

Use this link to see component photos of the cranks and the chain ring specs:
http://www.sudibe.de/renntandem_teile.html

Per the site, cranks are Ultegra with 53/39 drive rings and 48t timing rings.

[Hermes]

Aeroboy, I think you are focusing on interesting but less important things with respect to tandems. Like road and track racing, tandem racing and performance riding are about team power, aero and power to weight ratio. Q-factor is an interesting discussion but IMHO, not where the action is.

Racing to Win

In our racing club, we have several racing tandem teams, ad hoc teams designed to win tandem races and tandems designed specifically to win a race e.g. the US National Championships. Parties and teams competing are P/1/2s and are US National and district champions.

One objective is to port over to the tandem as much single bike equipment i.e. racing wheelsets as possible and select as appropriate for the race, wind and terrain conditions.

Specially designed tandems to allow the captain and the stoker to have aero bars.

Team selection to fit into age groups and gender pairing i.e. YY, XX and XY teams where a particular team has a competitive advantage.

I am sure that the Canadian racing teams do similar things for your District and National events.

Gearing selection is done for the course and the race.

Performance Riding and Local TT Events

Teams riding the tandem in group rides or events ride the regular offering of Santana, CoMo, Cannondale, Trek and etc. I generally see triples but we have a lot of long steep climbs and on the tandem it is nice to be able to cruise up mountains.

Couples who are strong individual racers are great on the tandem.

Recreational Riding

We see a lot of tandem couples riding for recreation and who appear to have disproportionate abilities and the enthusiasts within this group seem to focus on equipment. We see a lot of very schwaggy tandems. To climb the hills in the bay area, they need very low gearing just to get around and we do not see them on the major climbs.

As always, YMMV.

Good luck with your purchase.

[aeroboy]

Aeroboy, I think you are focusing on interesting but less important things with respect to tandems.

I tend to be obsessive about certain details and q factor is one of them. Actually it has nothing to do with racing the tandem because that is not the primary purpose of the machine. Exotic? Think again. This will be a family machine and by today's standards will be heavy. It will have 48 spokes front and rear. What it comes down to is that I happen to be dialled in with respect to things like q factor and crank length, as well as my position on the bike, and strive for consistency between the bikes that I ride. I ride better and with no knee pain using 165 cranks than with any longer length, and with less foot pain using the narrower q, plus I would prefer not to feel like I am riding a MTB/touring bike when riding the captain's position. I figure that if I'm going to spend car $ on a custom bike, that it might as well have as many things as possible the way I like them.

[Hermes]

FIne...get whatever you want or need, I was responding to this..."I would love to get into the tandem racing scene, especially TT events." and this 'The people I would likely pair up with in races (my wife and training buddy) are or have been licensed racers, putting them into the elite category, and I am a current Worlds medalist (track). Our own experiences shape our perceptions."

[bikeriderdave]

Yes, you SHOULD strive to match your single position on the tandem. But you will drive yourself crazy trying to "optimize" things for young stokers or a variety of stokers. Most people -- and, I dare say ALL kids -- will be much less sensitive to position variables than you are. You should also consider that a Periscope may not even shift well with a "low Q" stoker crank, because the rear seat tube OD (1.5 inches) limits inward front derailleur movement.
Because this is your first tandem (and because it seems that you are not quite sure how you will use it), why not buy a "stock" configuration and modify it to suit as you go? In a few years, you will know what works for you and will actually have a basis for custom tandem decisions...

[Cavalão]

Use this link to see component photos of the cranks and the chain ring specs:
http://www.sudibe.de/renntandem_teile.html

Per the site, cranks are Ultegra with 53/39 drive rings and 48t timing rings.
Sorry to dig up an old thread, but I'm researching a single sided setup myself... looking at the photos in this link, it appears to me the stoker stem is not an Ultegra and rather some cheapie crank... I am guessing there wasn't room to put the chainring outboard on the Ultegra? Which means no can do for Dura Ace as well. :cry: