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Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

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Old 12-30-09, 06:43 PM   #1
fkfw
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I really want this tandem to fit...

I'm looking at a tandem that measures 54cm for the captain. This will be my first tandem so I have only my road bikes to compare top tubes with. The top tube on my road bike is 57cm which is about an inch difference between the two bikes. My road bike has an '01 OCLV Trek frame. The person who owns the tandem now has the same inseam I do but clearly a shorter torso. What are the handling implications of making this bike fit my longer torso? I REALLY like everything else about this bike so I'm trying to find a way to make it fit. Unfortunately, I don't live close enough to the bike to test ride it. I'll consider getting on a plane and do so if I think I can make it work. Thoughts?


Thanks,
Jeff
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Old 12-30-09, 08:02 PM   #2
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a little bit shorter and more upright position will be fine for the tandem versus your road bike especially at first as you get used to piloting the bike. for me i seem to have a lot more weight on my hands and arms than on my single bikes because you have to control the weight of two riders and so i run the tandem with a cm or two shorter stem and a little bit taller instead of being really stretched out like on my race bike.

there are no handling implications from the top tube differences since the tandem wheelbase is so long, it will be completely different from a single bike no matter what.
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Old 12-30-09, 08:27 PM   #3
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There's also the possibility of substituting a longer/shorter angle stem, to take up part of the 3 cm difference. Assuming you have a fairly neutral length stem for the longer top tube you're currently riding, that should get the reach where you want it. And I agree that the handling is going to be different anyhow, and slightly more upright will be better.
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Old 12-30-09, 09:42 PM   #4
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Easy enough to get a longer stem or, as stated above, one with a bit more rise.
Also there may be some room to move saddle back a bit.
And yes, totally different handling for tandem/single.
If the rest of the tandem fits your team properly, this is not a deal breaker.
Pedal on TWOgether!
Rudy and Kay/zonatandem.
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Old 12-31-09, 01:18 AM   #5
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When deciding on the size of our tandem, I did not consider the reach that my stoker would need, which was a mistake. She has a long torso, and so needs her bars to be right up under my seat. My seat is therefore a lot further forward than I would normally have it to accommodate this. To get my reach right, I've now had to go to a 130mm stem, whereas I might normally use a 110mm stem given the top-tube length.

I never realized that the two rider positions would interact like this until we started playing around. Next time (if there is one), I think we'll go for a custom build to get the fit right for us both more easily. Simply getting the next size frame would not have been better - it would have been too tall and so would have caused other problems.
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Old 12-31-09, 02:31 AM   #6
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Thanks, everyone. This is good to hear that people prefer a more upright position when two-up. My road bike is not a stretched out fit like a typical race bike. I have a 100mm stem that is flipped and pointing up for a somewhat more relaxed position. The stoker size is ideal. This is a custom built tandem for someone else and the stoker, at 57cm ironically, is the size I need for the captain so plenty of room for a stoker that is 5'6". I'm sure I can slip the seat back a bit and pop a 120mm stem on there for fit but will a longer stem decrease stability at all? Or is a longer stem preferred on a tandem to slow the steering down a bit?

Jeff
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Old 12-31-09, 07:18 AM   #7
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Originally Posted by fkfw View Post
I'm sure I can slip the seat back a bit and pop a 120mm stem on there for fit but will a longer stem decrease stability at all? Or is a longer stem preferred on a tandem to slow the steering down a bit?

Jeff
There is a right place for the saddle, and it is not a matter of distance to the bars. It is all about getting the knee joint in the right place. Moving the saddle back a little may work, but moving it more than about 1 cm back from optimal is liable to give knee problems. On the other hand, the right place depends on the rider, which is why they are adjustable.

As far as the longer stem decreasing stability, I would expect the opposite. A short stem means a shorter lever arm on the steering, so a small amount of motion means a larger amount of turn. At low speeds you don't need to push all that hard on the bars to turn (at high speeds more of the turn is controlled by lean). Which means it's more about how far you push the bars than how hard. The longer stem means you are pushing further, which is likely to mean more stable.

However I don't have experience with playing with stem length on a tandem (only a single, and I don't steer my single with the bars at all, unlike the tandem).
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Old 12-31-09, 12:29 PM   #8
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That's what I thought - that it would slow down the steering a bit and add stability. As far as knee placement goes, the issue will be whether or not I can match what I have on my road bike which I set by hanging a plumb line from my knee that bisects the pedal spindle below it. From there I tweak the seat and bars a little. I can take all my measurements from my road bike and compare them to this tandem, throw in folks advice about "being more upright" and see how it feels. I've been riding one road bike for the last 8 years so I know what feels right to me.
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Old 12-31-09, 01:50 PM   #9
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I can take all my measurements from my road bike and compare them to this tandem.
This is the right next step. Be sure to look at and compare all of the key dimensions...

1. C-T-C Top Tube length, which you've covered.
2. C-T-T Seat Tube length, relative to how long your seat post will need to be.
3. Head tube height, to get an idea of where your bars will fall in relationship to your saddle height so you can get an idea of how much rise your bars / stem will need. Given that the steerer is already cut on the tandem's fork, this is one you'll really want to pay attention to.
4. Standover height... shouldn't be a problem, but always good to check just the same.
5. Crank to front wheel axle, relative to toe clearance / overlap. Smaller tandem frames tend to have less toe clearance so, once again, this is a dimension to look at so that you don't find yourself surprised by having a minor overlap condition.
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Old 01-12-10, 07:54 PM   #10
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Just wanted to follow up. I ended up passing on the tandem in question because after doing the math with all the measurements, it was just too small. It would have required something like a 160mm stem to fit. I really wanted this tandem and I was pretty bummed about having to let it go. The seller is a super nice guy who loves this tandem but has to sell it for health reasons. We really hit it off and he was sad that I had to pass on it as well. If you are looking and 54cm is your top tube size you should have a look at this custom Erickson: http://orangecounty.craigslist.org/bik/1549757479.html

It deserves a good home - just wish it could have been mine.
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Old 01-12-10, 08:11 PM   #11
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If you are looking and 54cm is your top tube size you should have a look at this custom Erickson: http://orangecounty.craigslist.org/bik/1549757479.html It deserves a good home - just wish it could have been mine.
I can see why you wanted the bike to fit.... That will be one heck of a deal for someone.

There were only a couple of the Scandium Ericksons built, literally... I think there are just two, perhaps three or four at the most.

We have owned two steel Erickson tandems; a '98 that we still have and an '02 S&S model that was sold to help defray the cost of our Calfee S&S tandem back in the fall of '07.





Photos are linked to larger images....
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Old 01-13-10, 12:32 AM   #12
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Speaking of tandem fit....does anyone happen to have the top tube (captain and stoker) geometry for a trek t1000? I'm in the market for a used tandem so my 10 year old son and I can ride together. Seems like Cannondales and Treks fit the budget. The Cannondale site has great info on their old frame geometries (looks like an X/S would fit us - I'm 6'3" and he's 4'6") but I can't find anything other than seat tube on the Trek....my guess is the 54/44 combination would be a possibility, but I'd sure like to know the top tube dimensions? Thanks in advance..and any advice for a tandem newbie would be appreciated!
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Old 01-13-10, 10:53 AM   #13
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The Vintage Trek site has some information, including a reference to the trekbikes.com site, where you can check out their archives for component listings on various bikes; no geometry, though; here's a sample for the 2003 model year T1000

http://www.trekbikes.com/us/en/bikes/2003/archive/t1000

you could - and this would probably be accurate within an inch or so - do some measuring, figuring, and computing based on the catalog/website photos. Print the image as big as you can, measure a known item like the wheel diameter and then figure out a basic "scale" (metric ruler will help).

The Vintage site lists a few of the model year / frame color matchups, for what that is worth (maybe for confirming the age of the bike when you find one)

02, metallic green
03, starry night black
04, platinum silver
05, titanite black


Geometry on the post-Y2K Trek aluminum tandems is probably different from the steel frames from last century; frame sizes certainly vary.

Your son will surely be growing, so an adjustable stoker stem for him will give you a few more years of usefulness; for the captain's position, a different stem length would be no big deal.

And, if you get a great deal on a larger-framed bike, you could always fit a set of "kiddie cranks", so that when his growth spurt hits at age 13, 15 or whenever, he can still ride with you (or you can swap off and let him be captain)
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Old 01-14-10, 12:53 AM   #14
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Thanks, Moleman, for the advice on scaling it...I'll have to pull out my old engineering school scales and blow the dust off. Appreciate the added comments, too.
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