Tandem Cycling - Stoker handlebar position
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11-19-03, 10:04 PM
My wife and I are proud new owners of a Burley Rock and Roll tandem we got for a great price this past weekend. We are new making all the adjustments, and I have one question. It has an adjustable stoker stem, and even setting it at the shortest position, the seat to handlebar distance is significantly shorter than that on her road or mountain bike. I can solve this issue by installing a fixed length stem 110 or 120 mm, but then I started thinking...should I be using her other bikes (which fit well) as the correct distance or are tandem stokers naturally using a shorter distance? Any advice before I go out and buy a short fixed length stem? A similar question is regarding the handler height, should I use her current bikes as a gage, or should I set those higher, which may be more comfortable?
11-19-03, 11:18 PM
Generally speaking, the stoker is often slightly more upright than the captain. Therefore, if both of you normally ride your single bikes with approximately the same position, your wife would be slightly "straighter" than she is on her other road bike. So you may try raising that stem to see if it helps.
Regarding replacement stems, many manufacturers make adjustable ones. The adjustment range is approximately 20-30 mm.
Also, if your wife stokes and if she has longer legs than you, you may need a stem with a right angle, so her bars would be higher than your saddle.
Finally, does she use stoker bars or road bars? Road bars would put her hands a bit further away than stoker bars.
11-20-03, 01:08 AM
Thanks for the reply.
The bike originally came with an adjustable length stoker stem, but the minimum length is HUGE, nearly 200mm. All the adjustable stems I have found have a minimum length much longer than fixed length stems, which vary between 110 and 130mm. The Rock and Roll is officially a mountain bike tandem, and came with mountain bike handlebars, though the large majority of our riding will be on the road. We chose a "riser" bar for my wife, which gives us some flexibility to add height to the bar, even if we choose a short stem that attaches to her handlebar under my saddle. Plus, we will add bar ends to it to give more hand positions. Without a doubt, she will be more upright, with the bar height capable of being higher than her seat height. It's the length that I'm wondering about. With the current "cockpit" her length from seat to handlebars on the tandem would be a few inches shorter than the equivalent space on her road or mountain bike. Is this also typical on tandems, or should we try to get the same cockpit length she has on her single seater bikes?
11-20-03, 07:34 AM
It's the length that I'm wondering about. With the current "cockpit" her length from seat to handlebars on the tandem would be a few inches shorter than the equivalent space on her road or mountain bike. Is this also typical on tandems, or should we try to get the same cockpit length she has on her single seater bikes?
Yes, it is unfortunate but true that most stock tandems are designed with stoker compartments that don't allow a proper fit for stokers who have been properly fit to a personal road or off-road bicycle. Back in the 80's, 25" stoker compartments were not all that uncommon. Burley used a 26.75" stoker compartment for many years. 27" - 27.75" seemed to be the more popular rear compartment in the 80's by the 90's some grew to 28.25" - 28.5" which is still too short to allow most stokers to achieve a natural riding position that replicates what they would ride on their personal bicycles. In fact, many stokers -- knowingly or not, depending on how attentive their captain's are to bike fitting -- have their seats positioned well back of where they should be relative to the crank axles in an effort to extend the handlebar reach and/or to get out from under their captain's butt.
Therefore, if you're looking to replicate your stoker's single bike riding position you'll be hard pressed to do so on a stock tandem unless they are very short or just took up cycling and ride a "comfort bike". Is it essential that you pursue a better fitting tandem? That's a personal call. Keep in mind, of the ~5k or so tandems probably sold in the US each year, only a very small percentage are custom made. Therefore, you'll find that many stokers are riding on tandems where they can't achieve a fit that would match what they would use on a properly fitted personal road or mountain bike. So, it's not necessarily an insurmountable issue, just another consideration.
I've never read a good reason for why proper stoker fit and comfort isn't considered a critical factor in the design of a tandem frame, but the often cited reasons for not providing longer top tubes include issues regarding the loss of aerodymanic advantage, harder to communicate, and amplification of excess stoker movements. What I believe is at the root of the issue is demographics. Historically, the largest group of tandem buyers are more mature couples who -- based on what I've seen and been told over the years -- prefer the more upright riding position. In fact, when Santana lengthened its rear stoker compartments from 27.75" to 28.125" (or is it 28.250"?), there were some unhappy campers who need to get longer stoker booms for their new Santanas.
The only builders who have long recognized that the average stoker needs more room are Erickson, Rodriquez (custom builders in Seattle, WA) and Ventana Mountain Bikes USA (MTB fabricator in Rancho Cordova, CA). All of Erickson's and many of the Rodriquez tandems are built to order. Almost every Erickson made features a rear stoker compartment in excess of 30" as do most of the custom Rodriquez models (Note: Erickson & Rodriquez started off their carries as R&E Cycles in Seattle and Glenn's first tandems were all sold under the Rodriquez brand name -- which explains the close ties even years after Glenn & Angel parted company and after Rodriquez sold his brand). Glenn Erickson is perhaps the original stoker-advocate when it comes to tandem frame design. Ventana builds all of it's off-road tandems with a 30.5" effective rear top tube, again, to give stokers the room they need to achieve a proper fit. It's probably worthwhile to note less than 500 Erickson tandems have ever been built and less than 500 Ventana tandems as well.
Other builders will take custom orders for tandems with extended rear compartments and of late Meridian Tandems has upped it's standard stoker compartment to a length of 29.375", which is about 1" longer than any other stock tandem. Some do a better job of designing the longer frames than others and, back to the reasons for long tandems, long framed tandems do require a more practiced technique to minimize stoker-induced steering corrections. Like all things, over time a team that is predisposed to want a high-performance tandem that is fitted to their ideal riding positions will quickly adapt to the qwerks of their tandem -- and all tandems have handling qwerks.
Personal Perspective: I'm 5'8" and Debbie is 5'2". Our first road tandem was a small size '96 Santana with a 28.25" rear stoker compartment. Once she acclimated to cycling, Debbie felt a bit cramped on that bike. We discovered and subsequently purchased our first Erickson in '98 and it features a 31" rear top tube -- Debbie loves it and will no longer ride on a "short" tandem. Our first off-road tandem was a Medium/Small '98 Cannondale MT3000 which had a 28.5" rear stoker compartment. After taking delivery of the Erickson, we ended up with a Ventana off-road tandem. We now have two Ericksons and are on our 2nd Ventana.
11-20-03, 11:20 AM
Thanks livngood for your detailed reply.
After reading your response, I decided to measure the stoker top tube distance. Since it is a softride suspension, I just measured the center to center distance of the two cranks, and found it at 27", definitely on the short side.
Your comments about alternative tandem choices are very good, and we will keep this in mind. Right now, we will keep this tandem (we just bought it this weekend!) and have some fun on it and find out what we like, don't like, and how much we will actually use a tandem before committing some serious money.
So, given all this, I'm leaning towards getting short fixed stem that will allow my wife to be a bit more stretched out. Maybe not quite as long of a cockpit as with her single person bikes, but significantly longer than with the current stem. It is interesting that the fixed length stems seem to be built between 110mm and 130mm, while the adjustable stem I have has a minimum distance of 200mm!
11-20-03, 11:49 AM
You might want to check with TandemsEast or one of the other tandem-specialty dealers as I believe there are shorter (5.75 - 8.5" projection) stems available:
Obviously, some adjustable stems can be shortened a bit by hacking off an inch or two from the handlebar clamp boom that slides into the stem's base.
As for fixed stem lengths, I have ones in use that range from 85mm - 100mm (Ritchey WCS) so I know they're available as are the shim's needed to reduce the clamp diameter to fit your Burley's (26.6mm?) seatpost.
Given that seat tubes will not vary much from 73 degrees, and that most stoker's horizontal-center-of-seatpost-to-center-of-handlebar spacing can be set on most tandems with the horizontal stoker stem length taking up the remaining distance between the seatposts, it is clear that the horizontal bottom bracket spacing sets rider spacing on a tandem.
What is generally not clear in today's market is the answer to this question: what is the best rider spacing from the stoker's point of view, expressed as a multiple of the spacing between the stoker seatpost and handlebars, or as a fixed number of inches in excess of that, given no limitations set by materials?
Material limitations in part led to current design. Older tandems made with less satisfactory tubing were reported to have flexible frames that tended to twist and oscillate due to aggressive steering and imperfectly coordinated riders. The solution was to make the rear end of the tandem as short as possible, thereby shortening the entire frameset, and keeping the frame flex to a minimum. Modern tubing and better frameset designs permit a wider range of fits, but the market still prefers tandems that look like all the other tandems, and with the average female height in the country being around 5'4", with a horizontal fit of 23" or so, tolerable (barely!) stoker fit can be had on a typical Santana with a stoker stem of 150mm or so. Bill McCready (Santana) absolutely insists on staying that short, saying that anything longer decreases the drafting effect of having the riders close and raises the power requirement. This sort of fit does impose some limitations on stoker position (can't put head down to prone because in many cases it won't clear captain's butt) and makes standing difficult.
But....National tandem time trial championships are generally won on long wheelbase custom tandems with stoker compartments long enough to permit some kind of triathlon-type aerobars in addition to stoker single bike fit. This narrows the stoker position enough to improve aerodynamics, though on a few bikes, having achieved the narrow position, the stoker hand position at the forward end of the aerobars is set near the captain's seatpost to keep close rider spacing for better drafting.
Given a blank sheet of paper, and a custom tandem budget, I would be inclined to set the bottom bracket spacing to accommodate the single bike seatpost to handlebar dimension of the most frequent stoker, plus room for aerobars, which might be about 15", depending on rider sizes (you have to consider whether or not the captain's saddle imposes limitations on aerobar position that matter.). The neat thing about this sort of rule is that you can generously fit female stokers of average size, fit female stokers who are larger than average, and fit men of average size or a little larger with their normal single bike fit, though in that case the aerobars are backed up some. Instead of the limiting factor being the horizontal spacing in back, the limiting factor tends to be how far you can safely run the seatpost out. After you have spent a hunk of money on a tandem, surely it should fit as large a portion of the population as possible without consequent disadvantages?
Wind gusts to 40 mph out of the south are predicted for North Texas today. I'm going to take the 12-23 off and put the 11-23 on the rear end. Gonna need the 11T today....
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