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Thread: Tandem sizing

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    Tandem sizing

    I have been interested in getting a tandem for our family, but am confused on sizing. I am 6'3, and ride a 62cm bike. My wife is closer to 5'3". I have seen many used tandems advertised as large or medium. Others are measured in inches. Could someone set me straight on about what size tandem to be looking for?

    Thanks

    Steve

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    hors category TandemGeek's Avatar
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    949Short answer: You probably should be looking for a 24 or 25 x 19, aka. Extra Large/Medium.

    -------Details------------

    Upright tandem frame sizes are usually expressed as a front/rear, e.g., 23" x 18" or Large/Medium. Some builders only use one size, e.g., Small, Medium, Large, Extra Large which pertains to the frame size relative to the Captain's position with a proportionately, slightly smaller riding position for the stoker. These builders assume the stoker's seat height isn't as critical as the captains relative to their ability to touch the ground since it's assumed the stokers will stay clipped-in from the time they start riding until they're done; similar to riding a horse. The captain, on the other hand, will have to have a proper fit so they can safety mount, start and stop the tandem with the stoker clipped in.

    As for how to establish the proper sizing for tandems, it is arrived at in the same way as single bikes. Assuming you're talking about purchasing a road tandem, the approximate seat tube or frame size to look for can easily be established through multiplying your inseam by .64 (64%). The result will be the approximate seat tube length you should be looking for.

    For instance, if you're riding a 62cm frame right now I'd assume you have an inseam of approx. 37" - 38". Since you already know you ride a 62cm frame simply convert that into centimeters (divide by 2.54) and you'll find you should be looking for a tandem with a 24" - 25" long seat tube at the front. This would be an "Extra Large".

    For your stoker, at 5'3" let's assume she has an inseam of about 30" - 31". Multiply that by .64 and you'll find 19" - 20" (49mm - 50mm) is about the right size. This would either be a Small or Medium depending on the builder.

    So, what you're looking for is a 24 - 25 x 19, aka. Extra Large/Medium. Obviously, this is nominal and not exact but it will at least put you in the ballpark.

    Some dealers would most likely have you try out a Large sized tandem (23") and perhaps suggest that an extra long stem would give you the right fit: be skeptical. A really good dealer would ask you to take the measurements off of your single bike (reach, seat height, saddle set-back) so they could compare your fit requirements to their stock-sized tandems before making a recommendation.

    Here's a snap-shot of what's available:

    -- Cannondale makes a 25 x 21 (Extra Large/Large) which could be made to work if your stoker was willing to live with a top tube to straddle when they get on and off the tandem (see note above regarding stokers). They also make a 23 x 19 (Large/Medium) which might be a touch too small for you but perfect for your stoker.
    -- Bilenky in Philadelphia also makes stock-sized tandems in a 23 x 20, 24 x 20 and 25 x 19.5
    -- Co-Motion makes a 23 x 18 and a 23 x 20: Custom size available for a few bucks more.
    -- Santana makes a Large and Extra Large and seem to be offering custom size on their higher-end tandems for very little extra cost.
    -- Burley makes only a large (23" x 18")
    -- Meridian will build you a tandem to order for not much more than a stock-sized bike from it's competitors (Call Jim Leis at MeridianBike.com)
    -- Bushnell will make a custom sized tandem for about the same price as a stock size since they build all of their tandems to order (just deal directly with Dennis Bushnell).
    -- There are others but these are the ones that immediately come to mind.

    Bottom Line: If you have the opportunity to take a test ride on a few tandems do it sooner rather than later. This will give you a chance to really figure out what size ranges will work and/or if you'll really benefit from a custom-sized bike. You'll definitely want to write down your and your wife's bicycle dimensions before heading off to the shop so you can borrow a tape measure and check the in-stock bikes.
    Last edited by livngood; 04-01-03 at 05:28 AM.

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    Dang Mark, if you are not in the industry, you should be. You've got more know how pertaining to tandems than any bike shop I've ever visited (I'm in the industry and I've been to hundreds of bike shops). When ever I have a question, I just post it here in hopes you'll check the site and tell me what I want to know. On second thought dont open a shop, because then you'd charge for your knowledge.

    Steve, I ride a 23 Co-Motion and I'm 6 ft tall. I have no doubt that this size would work for you with the proper stem size. I have loaned my tandem to someone 6.2 with a 100mm stem that worked out great.
    My wife is 5 10 so we have the 23X20 I'd think you'd want one size smaller for the stoker.

    Go to the Co-Motion web site and fill out the "fit chart" and send it in to Dwan. They'll be able to tell you what you need. Co-Motion is the only high end tandem I've ever owned so, I cant give you any other names that I've actually put miles on as our other tandem was a Trek hybred that was given to me (wouldnt suggest a hybred to anyone).

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    Mark and Brad -

    Thanks for the sizing info and for the bike recommendations. This clarifies things for me.

    Appreciate you taking the time.

    Peace

    Steve

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    hors category TandemGeek's Avatar
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    Originally posted by brad
    Dang Mark, if you are not in the industry, you should be. You've got more know how pertaining to tandems than any bike shop I've ever visited (I'm in the industry and I've been to hundreds of bike shops). When ever I have a question, I just post it here in hopes you'll check the site and tell me what I want to know. On second thought dont open a shop, because then you'd charge for your knowledge.
    I'm humbled and not worthy. And to prove it let me point out that I had a senior moment when I wrote my note (I have a problem with keeping numbers straight - dyslexia limited to numbers, if you will) Anyway, the number that I should have used is .65 (65%), not .64.

    I don't think it will change the answer too much but I would point out that some bike fitters / calculators use a factor as high as .67 (Colorado Cyclist is one of them I believe). Again, they're just starting points -- they key is finding a bicycle that fits you well and then writing down those numbers for future reference. My bikes are all funky when it comes to size -- but so's my body.

    Getting back to the factors, .65 assumes you're using a Center-to-Center measurement: that would be center of the bottom bracket to the center of the junction of the seat tube with the top tube. I'm showing my my age. Center-to-Center works fine with conventional frame designs but is nearly meaningless in the age of slopping top tubes and compact frames. The other factor I mentioned, .67 is used as a reference for bikes that are sized based on the Center-to-Top of the Seat Tube which is what is more common these days.
    Last edited by livngood; 04-02-03 at 08:26 PM.

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    Senior Member JustsayMo's Avatar
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    In my limited experience (two tandems) I would say the captain should buy a tandem with a similar top tube length to their single bike.

    I purchased a tandem based on my seat tube length and the top tube is WAY too long for me.

    I typically ride a single bike with a 55 cm top tube. The tandem I mistakenly purchased has a 60 cm top tube and even with a short stem and the seat scootched all the way forward I'm still 2 cm longer than my road position. I can mount/dismount and stradle the tandem easily. The seat tube length is fine.

    2 cm may not seem like much but after an hour of riding I'm ready to get off. My previous tandem has the same seat tube length with a shorter top tube. I did Centuries and Double Centuries on it without comfort issues.

    Anyone want to buy a Cannondale RT-1000 in nearly new condition?

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    I may be wrong, but the trends in bicycle frame sizing seem to have shifted from one that emphasizes seat tube dimensions to one that focuses on top tube length. IMHO, it is far better to focus on the top tube length and adjust the seat post height than to try and squeeze onto a frame with a shorter seat tube jus to get a more rigid frame and perhaps lower center of gravity.

    That being said, I am also in a bit of a sizing quandry. My wife and I are sold on a Co-Moton Speedster with a carbon fork, but we seem to fit smack dab in the middle of the medium and large frame sizes.

    I currently ride several road bikes with 23 inch (roughly 57.5 to 58 cm) top tube lengths and 11 cm stems. I also have a 35 inch inseam. I sent all of our measurements to Alan at Co-Motion and he and the rest of the folks at Co-Mo suggested that we purchase a large/med frame set with an 11 cm stem. My problem is that while I beleive that the large is correct for our inseam measurements, the top tube on the large frameset is 23.25" (59 cm). I spoke with Alan and he said that they thought that the 11 cm stem they recommended was as short as they would like to see anyone go on their tandems. So there I am, trying to get comfortable with the idea that I am going to buy a $4500 tandem (upgrades included) that has a top tube that seems to be a bit long and a stem recommendation that is hard up against the minimum length for proper handling.

    I think I know what I need to do and that is visit a Co-Motion dealer that has a full size run (unlike the one here in Albuquerque) and actually get fitted on a large frameset. Then I can go ahead and determine if we can fit on a large/med or if we need to spend a few more $ and shorten the top tube to meet my current road specs. I guess our next trip is to Denver (8 hour drive) for a true sizing session.

    Any thoughts regarding the stock Co-Motion sizing would be much appreciated.

    Rgds,

    Steve

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    Senior Member JustsayMo's Avatar
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    Hi Steve,
    What is a few hundred more for custom sizing after $4500

    We were in a similar situation with CoMotion and ended up going with custom sizing.

    My advice if you do go custom is speak directly with Dwan. I'm still not sure what the heck Alan does there. Go over the details and confirm them and then do it again. As great of a Tandem builder CoMotion is they are still a company with a long chain of communication. The word doesn't alway make it to the guy with the torch.

    Once we took delievery of our Custom Comotion tandem we have been very satisfied. The details are well done, the frame was perfectly straight and required very little in the way of prep to assemble (comparitively).

    I have a few custom bikes (road & track) and could never go back to my stock bikes (and be as happy). This was our first custom tandem and the difference between it and our previous two tandems is significant. It was well worth it to get the fit I am comfortable with. My wallet might be lighter but my butt is happy.

    Mo

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    Mo,

    I hear what you're saying about the few extra $ to get it right. I don't mind spending it either if that is what's required. I too have gone the custom road bike route and have not been disappointed.

    The key issue is finding out if it is necessary. My wife and I talked about things this afternoon and we decided that we need to make a trip to Tandem Cycle Works in Denver just to make sure that the fit is right. If we can get away with stock, cool. If we need to cut 1-2 cm from the top tube, we will go with that change.

    It's difficult when the only CoMotion dealer in the state (Albuquerque, NM) only has small frame sizes. It's a bit much to trust that the size will be correct when the better part of $5k hangs in the balance.

    I guess we will think about a trip up north within the next month.

    Thanks for the help,

    Rgds,

    Steffan Marley

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    SDS
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    Don't forget, shock-absorbing seatposts require room for travel. So the minimum height above the seat tube for a shock absorbing seatpost is greater than for a fixed post. If you use a fixed post, you can fit a woman of 5'2" on the back of a Cannondale pre-'98 J/L with a 23" seat tube (center to top), but when you set out to properly fit the back of a tandem that would be a very poor choice.

    I think the average female height in the USA is 5'4", but of course the average height of the population (men and women) is greater than that. If you look for the largest tandem on which your wife believes she fits well, you may be able to offer better accommodations for guest stokers.

    Your wife might find short cranks in the neighborhood of 165mm helpful if she has trouble spinning as fast as you, though I know of one woman of 5'2" who uses 175mm cranks quite well.

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    It's not really the seat tube that I'm worried about. I think that the CoMotion large (23" Captain/20" Stocker) is about right. I have a 35" inseam and my wife has a 33" inseam, so I thnk that the basic size recommendation from CoMotion is correct.

    My concern centers on the top tube, which, to me, is more important. I have ridden and raced over the past 30 years and have come to enjoy being stretched out on the bike with my back more or less parallel to the top tube. To do this, I have found that a 57.5 to 58 cm (22.5" - 23")top tube is required with an 11-12 cm stem. With the CoMotion top tube dimension at 23.25", it may be a bit too long. I say this because CoMotion themselves told me that they would not recommend going shorter than an 11 cm stem. So if I currently ride with an 11 cm stem and a 22.75" top tube and I add choose a tandem frame with an additional 1/2" of top tube length, I'm may feel stretched out a bit too much and have no "wiggle" room if I need to go to a shorter stem.

    I will have to visit Tandem Cycle Works in Denver (closest to me) to make sure that I know what to order before plunkin' down the bucks.

    As far as seat posts go, we have ridden with both the solid and the shock absorbing types and I guess we are so used to regular road bikes that the solid types work out best for us.

    Thanks for the input and help. We will get it all sorted out soon and will have the right tandem in the right size. It just may take a bit more driving that we had planned!

    Rgds,

    Steffan Marley

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    Senior Member JustsayMo's Avatar
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    Hi Steffan,
    I think the "wiggle room" factor is very important. While I was able to duplicate the exact position of my road bike it was less comfortable on the tandem. I believe reason is I spend a LOT more time seated on the tandem than I do on my single bike so a lower stretched out position was more fatiguing.

    By simply adjusting the stem height and saddle relation to that I was able to achieve a comfortable "all day" position even though it's slightly different than my "all day" position on my single bike.

    Best of luck! It sounds like you are doing all the right things to get a most excellent tandem!
    Mo

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