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  1. #1
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    Not quite happy in the saddle

    Well, I am near the end of my options, so it is time to cast about for other ideas. I got into tandems last year at about this time. I meticulously (ok, not quite so meticulous as it turned out) built the captain's area to be as close as possible to my single bike, which I am totally comfortable on. This required lots of changes to stems, etc.

    I have never been completely comfortable on the tandem. The primary point of annoyance is the right sit bone. It gets sore, and eventually the whole right leg starts to feel like it is not right. I have measured and tweaked over and over to get it identical to the "control" position on the single. [Seat height from BB axle, seat setback from BB axle, seat setback from handle bars, seat angle] After I really really got them as identical as possible, I am still having problems. So it has to be something else, right?

    The first thing I changed this year was the seat angle. I found to my surprise that the single bike saddle was a little down in front, maybe 1 degree (using a bubble, so I don't have an exact value). Changing the tandem to this made a big difference; I was able to last longer before the problems started. This also concluded all my efforts to make the position identical. I am as close as I can get.

    So I changed the saddle to be identical (Selle SLK). I had the gel version of the SLK on there before. This definitely helped a little. I now consider the Gel SLK to be a "bad" seat. But I still have the problem. It just takes 20 miles before it become noticeable, and 40 before I really start to think about it.

    But I still have the problem. I have the Eastern Tandem Rally, and the The Flattest Century in the East this summer. I need to be able to do 60-100 miles in a day. I am worried that I will not last.

    Remaining potential causes:
    1. The crank length appears to be different on the two bikes. 170 on the single (which is what I have always had), and the FSA Gossamer ones on the tandem appear to be 172.5. This is definitely a closely related dimension to the issue.
    2. The tandem sitting issue. I sit 99% of the time on a tandem. Because of stoker wrist issues, we rarely both stand while pedaling, and just me standing is a little wobbly, although doable. But it can't be done as much as on the single, where I stand a lot.
    3. The angle I am making to the saddle. I feel as if I am more upright on the tandem, even though I have gone to great efforts to match the positions.

    When I go from the tandem to the single back to back (which I often do, and now more eagerly do to try to isolate this issue), I notice that I feel slightly lower in the saddle and more flat in the back. Measurements do not bear this out, by the way. It is just a feeling.

    Another point: when I ride 25 miles on the tandem, enough to get sore, and then switch to the single, I instantly feel better, the problem goes away, and I can ride 35+ without a hint of a problem. This seems to kick out #2 above.

    There is something different about these bikes, and I can't put my finger on it. Any ideas? I would love to try 170mm cranks, but swapping captain's cranks on a tandem isn't a casual thing. And could that 2.5mm difference really cause all this pain?

  2. #2
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    #1 you gotta get out of the saddle and move around more often.

    #2 I bet you aren't pedaling at the same cadance or effort on the tandem as you are on the single. Likely you are pedaling a bit slower with more effort which is going to put more strain on your seat.

    #3 I like Brooks.

  3. #3
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    Seat tube angle?

    Also, the crank arm length difference of 2.5mm equals 5mm of change rotationally (2.5 at top, 2.5 at bottom). I think that is significant, but others may have a different opinion.

    While a commendable effort, I would concentrate on making the tandem comfortable, and ditch the effort of matching your single.

    Steve

  4. #4
    pan y agua merlinextraligh's Avatar
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    In my experience, long rides on the tandem are more of an issue for your butt, than on a single.

    I think it's largely the result of not moving around as much on the Tandem. Because you need to coordinate things, the tendency is to not stand as much and not move around as much on the seat.

    2 answers, 1) find a more comfortable seat, even if it means going with a heaver seat.

    2) change positions more. Force yourself to stand (even if it just 10-15 seconds while you coast.) Sneak in butt breaks. (for example, raising just slightly off the seat as you corner, with the weight on the outside pedal, raise just slightly off the seat anytime you're coasting, etc.) Sit on the back of the seat climbing, on the front of the seat spinning.

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    Quote Originally Posted by stevetone View Post
    Seat tube angle?

    Also, the crank arm length difference of 2.5mm equals 5mm of change rotationally (2.5 at top, 2.5 at bottom). I think that is significant, but others may have a different opinion.

    While a commendable effort, I would concentrate on making the tandem comfortable, and ditch the effort of matching your single.

    Steve
    Seat tube angle appears to be identical, but I am not using that; I am using plumb and level to position the seat relative to the crank axis.

    The crank length effectively makes the saddle 2.5mm higher (ignoring the top of the stroke). I noticed that the saddle was a little lower (than the single) after some careful measurements yesterday, and raised it 2mm. In a mile, I stopped and put it back down. Definitely the wrong direction. So, from this, I learn that 2mm definitely makes a difference, so the crank length difference could be a cause here. And, there is the feeling that the single is lower, even when it doesn't measure out to be. So maybe I need to lower another mm and see. I guess that is my next experiment.

    I would love to ignore the single and just go for comfort, but the single is my standard for comfort! Thus my energy to try to match it.

  6. #6
    hors category TandemGeek's Avatar
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    Quote Originally Posted by jgg3 View Post
    [Seat height from BB axle, seat setback from BB axle, seat setback from handle bars, seat angle] After I really really got them as identical as possible, I am still having problems. So it has to be something else, right?
    As you discovered, seat height from BB only works if you have the same crank length on the baseline bike and the comparison bike. The latter is why I use check pedal axle at the lowest position to saddle height. You must also account for any changes in pedal/cleat stack height if you use a different pedal or shoe system on different bikes. The difference between road & off-road shoes and the various different pedal systems accounts for a few millimeters of difference.

    1. The crank length appears to be different on the two bikes. Fix this first, as your tandem's saddle would be 2.5mm too high based on your earlier comments.

    2. The tandem sitting issue. This is a big issue and you'll need to incorporate 'butt breaks' into your riding regime, either incidental via riding out of the saddle more often such as on short rises or by simply standing on the pedals and coasting as often as every 10 - 15 minutes, but at least every 20 minutes.

    3. The angle I am making to the saddle. Short of using a FitStik, I've found the only thing that works reliably for me was putting a license plate on the seat with the level sitting on top of it and then finding something with the correct stack height to put under the license plate to center the bubble in the level. Since we both ride with about a 3* rise in the saddle noses on our bikes, a certain pair of needle nose pliers placed across the back of the saddle worked for me and a cresent wrench worked for Debbie's saddle. Changes of even 1* do make a big difference for us.

    The last thing about saddles that I'll mention is break-in. Even though I have six nearly identical Selle Italia ProLink saddles, the ones I ride the most often are the ones I keep on the tandems. The newer and less used saddles have on occasion ended up on a tandem and it's noticably less comfortable than the worn-in saddles. As noted, since most of us spend a lot more time off the saddle on our single bikes, my single bikes tend to get the newer saddles.

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    Quote Originally Posted by merlinextraligh View Post
    In my experience, long rides on the tandem are more of an issue for your butt, than on a single.
    Definitely true, but if you ride on the tandem, get sore after 25 miles, then jump on a single, do not stand up, just ride for a mile, and all your symptoms are gone and you have a feeling of complete relief, then it is hard to come to the conclusion that it is merely caused by sitting for awhile.

    This transition relief is what is really driving me. I just sit on the single and go "ahhhh". It is that dramatic. I know it can be better, I just need to find out what "it" is. And, each major step, changing the seat angle, and then changing the seat itself, has made a difference. I feel like I am getting there. So I am now looking at things that are much harder to change, or even test: the crank length.

    I guess I was hoping that someone would pipe up and say, "oh, yeah, I solved all my problems by going to <blank>."

  8. #8
    hors category TandemGeek's Avatar
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    Quote Originally Posted by stevetone View Post
    Also, the crank arm length difference of 2.5mm equals 5mm of change rotationally (2.5 at top, 2.5 at bottom).
    I originally learned (i.e., forced myself) to adapt to having the 170mm cranks on my single bikes, 165mm on my fixed gear, and the 175mm on the tandem per tandem lore. However, as the body aged I found myself to be less tolerant of the 175mm cranks on the tandem and moved back to 170mm in the fall of '06. It made a HUGE difference in terms of being able to spin a more efficient cadence and reducing fatigue on long distances or mountain riding.

    I'm now a strong advocate of captains & stokers using the same length cranks on road tandems and road bikes.

  9. #9
    hors category TandemGeek's Avatar
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    Quote Originally Posted by jgg3 View Post
    I guess I was hoping that someone would pipe up and say, "oh, yeah, I solved all my problems by going to <blank>."
    OK, here's a long-shot that's not as bizarre as it may sound. Does your stoker still have a habit of trying to look around your head to see the road? If so, and if she's been doing it since day one, chances are you're having to off-set your weight a bit to trim the bike's balance. The same malady can come from riding extensively on roads with a high crown.

  10. #10
    pan y agua merlinextraligh's Avatar
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    Quote Originally Posted by TandemGeek View Post
    I'm now a strong advocate of captains & stokers using the same length cranks on road tandems and road bikes.

    I take it that you're suggesting that the Stoker's crank should be the same length as their single bike's cranks, and the Captain's cranks should be same as on the Captain's single bike.

    Not that Captains and stokers of different heights should use the same crank lengths on the tandem.

  11. #11
    hors category TandemGeek's Avatar
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    Quote Originally Posted by merlinextraligh View Post
    I take it that you're suggesting that the Stoker's crank should be the same length as their single bike's cranks, and the Captain's cranks should be same as on the Captain's single bike.
    Correct. Stick with what works. There's no good reason to re-learn a pedal stroke just because you're switching over from a road single to a road tandem UNLESS there is an unreconcilable large disparity in captain/stoker cadence that warrants fitting the stoker with a shorter set of cranks (or visa-versa in the event the stoker is the spinner with the better developed stoke).
    Last edited by TandemGeek; 05-19-08 at 08:24 AM.

  12. #12
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    No one has mentioned Q factor and I'm sure no expert on it... but....while I have never gotten our tandem as comfortable as my singles I did make a noticeable step in that direction when I found that the Tandem's BB axel length was 122mm and my singles were much narrower ( around 110 as I recall). When I narrowed up the tandem as much as I could it did help some upper leg and hip discomfort...Good luck with your search for perfection jqq3.

    Bill J.

  13. #13
    hors category TandemGeek's Avatar
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    Quote Originally Posted by specbill View Post
    No one has mentioned Q factor and I'm sure no expert on it...
    If you're sensitive to Q-Factor it tends to create problems with the hip or knee joints and tendons.

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    I have 3 bikes-2 singles and a tandem. The tandem has 175mm cranks and the singles have 172.5 and 170. As I added the 2nd and 3rd bike I took the measurement from the center of the pedal at the bottom of the stroke to the top of the saddle, as opposed to the center of the BB to the top of the saddle. Once that's close I just fine tune each one until they feel "right". I have no problems switching between the bikes although I can tell the difference in ease of spinning.

    Another suggestion, we've switched over to Selle Anatomica saddles and love them. They're leather (ala Brooks) and have a cutout so the 2 sides move independently of each other. If you look at someone riding one on a trainer you see that the 2 sides move up and down differently. They take a little longer to set up and are not cheap, bet they're well worth it for us.

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    An update on this issue. I believe the solution is the crank length. It turns out, the captain's cranks are marked 175 (FSA Gossamer), not the 172.5 I casually measured/assumed (hard to measure c-to-c while everything is mounted!). This meant that my "matched by measurement" position was originally 5mm too high, and this matched all the evidence. I have since measured off the pedal platform on the two bikes, and have it pretty much in the same place. This has correspondingly reduced the butt pain to a very tolerable "slight" effect after 40 miles, which could well be simply sitting time. I no longer feel one is higher than the other when switching between them.

    But I still would like to have 170 cranks. Is there a source for these? I assume I can put just about any 130mm bcd ISIS crank on the front, but that would imply the pedal threads would be reversed from normal (because the spider goes on the left on the tandem captain). Or do they just ignore this? I shall have to have a go with the pedal wrench to see.

    Anyway, thanks for the comments. Always helpful. The Net is amazing.

  16. #16
    hors category TandemGeek's Avatar
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    Quote Originally Posted by jgg3 View Post
    But I still would like to have 170 cranks. Is there a source for these?
    You might check with Co-Motion as they were at one time stocking the Gossamers in a range of crank lengths. Of course, this could have been before the current tandem cross-over crank set drought set in with just about all of the suppliers, e.g., FSA, TruVativ, Shimano, and Martec.

    Of course, there are a few other options:

    1. daVinci offeres a very nice square taper crankset for tandems in a full range of lengths. They've also started to offer black anodized rings and arms on a special order basis. In fact, I'm thinking about finding out if any other daVinci owners would like to go in on a 'group buy' to have their existing cranks anodized. The cost is about $100 per batch and it purportedly doesn't matter if it's a single pair or multiple pairs of cranks, i.e $100 for one pair / $10 for 10 pair.

    2. Peter White offers Specialites TA tandem cranks... also square taper, in a wide variety of lengths.

    3. As you note, for the captain just about any set of cranks will work up front so long as the BB interface isn't unidirectional. You just retap the crank's pedal axle threads or drill them out and insert a helicoil to correct the thread direction. In fact, I believe this is how R&E creates their Campy cranksets for their tandems.
    Last edited by TandemGeek; 04-15-09 at 05:36 PM.

  17. #17
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    Quote Originally Posted by TandemGeek View Post
    If you're sensitive to Q-Factor it tends to create problems with the hip or knee joints and tendons.
    +1

    On my first long rides on the tandem, I used the original Suntour "blaze" cranks 170mm length for both capt/stoker (my single uses 172.5) with a REALLY WIDE Q-factor (long spindle BBs).

    I noticed some hip/knee joint pain, and I think it was the Q-factor that caused it.

    I have since switched to a new DaVinci crankset. The captain cranks are 172.5mm and the stoker is 170mm. That's fine, but the big difference is the Q-factor. I am using 107mm bottom brackets for both captain and stoker, and the DaVinci cranks are more "low profile" I definitely noticed a difference in the Q-factor.
    Last edited by uspspro; 05-30-08 at 02:04 PM.

  18. #18
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    Quote Originally Posted by jgg3 View Post
    This transition relief is what is really driving me. I just sit on the single and go "ahhhh". It is that dramatic.
    The qualitative feeling you express says the that the fit is not the same. I would measure the seat to bar drop on both tandem and single along with the effective top tube length. Are they the same? Also, I would put the tandem and the single on the trainer and take pics of you on the bikes from the same vantage point. Does your position look the same? Are the angles of the body the same? I suspect that they are not. Good luck.

  19. #19
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    The issue is that you are extending your knees too far and over-stressing your hamstring muscle group, which partially attaches to your "sit bones" on your pelvis.

    This is how you solve the problem.

    Clip in one of your cycling shoes into the pedal for your solo bike. Measure the distance from the inside of the shoe sole with the crank arm at the 6 o'clock position to the top of the saddle. Make sure that the saddle is compressed if it is spongy. This is the dimension that must be transfered to your tandem. Follow the same process with the shoe clipped in and saddle compressed. This eliminates all variables involving shoe, cleat, pedal, etc.

    This works every time. Take your time, get it right, go for a long ride and enjoy the tandem.

    I work with biomechanics for a living as a sports doctor. I use this on my bike to ensure proper fit when making any changes to components or getting a bike set up properly.

    David

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