I have just recently purchased a used Burley Duet with a Softride beam and my wife and I love it. Getting the bike to fit her has been a breeze. The adjustment flexibility of a Softride beam is much better than a seat post. The beam takes some practice to get used to but she can now spin at 94 rpm without bouncing and I don't get in trouble if forget to call out a bump.
The first thing I did for me was to shorten the ahead stem from a 150 to a 90 cm. I have always set up my bikes so the handlebar obstructs my line of sight to the front axle.
Next, I lowered the seat post down as far as is possible and still want to go down .75" inches. The seat post clamp is this huge contraption that clamps to both the seat post with the top hex bolt and then to the seat tube with the bottom hex bolt. If I had a shorter one bolt clamp I am sure I could lower the seat down to give me a more relaxed leg extension. Is there a single seat post clamp that could adequately handle the stresses of the stokers handlebars and my fat ask?
Now I am having trouble getting the seat zeroed in to where most of my weight is carried on my sit bones. The saddle has been moved forward and the seat is comfortable. But, this position has unfortunately put the "ideal" verticle line from behind the knee cap through the center of the pedal spindle to 1.75" inches out in front of the pedal spindle. I normally ride a 170 mm to 172.5 mm crank and am wondering if I get shorter crank arms I could resolve my inefficient and uncomfortable position. Is there any good reason for having a 175 mm crank for the Captain while the stoker is using a 170mm? Is it ok to move down to the 170 or 172.5?
I have noticed that many road tandems I have looked at in the LBS have these large 46cm front handlebars. This Burley is no different. Although I should use this size of bar, I am much more comfortable on 42 cm shallow drop bar. Will the narrower bars make the tandem more twitchy and difficult to steer(lack of leverage)? I am new to tandems and would be grateful for any input.
Additional information: The stand over is 30 inches and my inseam is 31.
Oh, and if you're looking for a more simple solution, just set your tandem up to match your most comfortable single road bike's position. This can be done alone or more easily with a helper but what you'll want to do is to measure your single bike dimensions for:
1. Seat height: Measure from the center of the crank axle to the top of the saddle along a line parallel with the seat post.
2. Seat Set-back: Drop a plumb bob from the nose on your saddle down to your cranks and measure the distance from the plumb bob's center line (the string it's hanging from) to the center of the crank / bottom bracket axle.
3. Reach to Handlebar: Measure from the nose of your saddle to the center of the handlebars. (NOTE: Using line-of-sight techniques for bike fitting are not reliable, e.g., handlebars block view of hub -- too many variables).
4. Handlebar Height: Measure the distance from the ground to the top of your seat and then from the ground to the top of your handlebars and subtract to find the difference. Remember, you're after the vertical difference between your seat and the handlebars, i.e., how much lower or higher are they relative to your seat. Recreational tandems are normally set up with the handlebars a little bit higher than a single road bike. I think ours are about 3cm higher which is still pretty low compared to most.
5. Handlebar Width: Personal preference here. I used to use handlebars on the tandem that measured one size (44cm) wider than my single bikes (43cm). Over time I've started to fit my single bikes with the wider bars just to keep it consistent but, ultimately, it is normal to have bars that are one size larger on your tandem vs your single bike for added control.
6. Saddle Tilt: Check to make sure the surface your standing on is level with a short mechanic's or carpenter's level. Next, put a flat plate (I use an old license plate) on top of your saddle so that it rests on the high points at the nose and tail and then put your short level on top of the plate. Note the amount of tilt based on the position of the "bubble" in your level. (FWIW: After playing around with saddle tilt for about 10 years I finally realized that zero tilt works best for me).
Apply these measurements and settings to your tandem and you should be fine. Regarding the extra 5mm in the cranks, keep in mind that it's only 5mm, or .5cm or about 3/16". (.19"). That's not a whole lot and considering how much you move around on a saddle as you ride (forward when spinning, back when hammering) so it's not going to throw you off much at all going back and forth between 170mm on a single bike. Therefore, I'd set that factor aside until you resolve the overall fitting issues.
My stoker and I have a Look ErgoStem on our Calfee tandem, which allows a wide range of adjustment in handlebar position. We wanted to both be able to captain, and It's not only made that a breeze, but it also allows us to make small adjustments to try out different positions. It's every bit as stiff as a standard stem, albeit 1/2 lb. heavier.
I actually spec'd very narrow bars on this particular bike to give me LESS steering leverage, as the Calfee has the same steering geometry as a single bike. It is VERY quick in the steering dept. When we were comparing bikes before purchase it felt high-strung, but now that it's all we ride it feels great.
The "bars blocking hub" rule of thumb applied to racers using 1970s Italian road bikes. If you change the headtube angle and the fork trail, this becomes meaningless.
Dont change your cranks to fudge a fit. Cranks are the first thing you decide when fitting a bike . How can your saddle be in the correct position, when your feet dont reach the pedals properly. This IS the definition of correct saddle placement.
Once you have your feet-saddle relationship fixed, you then work out your handlebar-seat relationship.
Is this frame too big for you? Maybe you need more standover height, so the seatpost is not at its min extension.
If the stoker and pilot are different sizes, then they should be using different sized cranks. I imagine that you have to fix the pilot seat position, before setting the stokers stem.