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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 02-09-09, 10:41 AM   #1
duppie
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Stoker seat post replacement

All,
We bought a used 2004 Co-Motion Speedster Co-Pilot over the weekend. (I'll post a picture soon, hopefully)
It appears to be lightly used and in great condition. We took it for a testride, and returned to the seller with a big grin on our faces.....
The one issue that probably needs a quick resolution is the stoker seatpost. It is a after-market tapered seatpost. Therefore it has to stick out about 4 inches. Ideal height would be about 3 inches, but when i try that, it simply sinks in all the way.
So we are looking for a replacement. A thudbuster probably won't fit (and stoker doesn't seem to care for it much). Will a carbon seatpost have a noticable dampening effect? Is it money well spent? or should I simply go with an alloy seatpost?

Thanks, Duppie
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Old 02-09-09, 11:37 AM   #2
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First, you have to decide if your stoker needs/wants a suspension seatpost. If she does, then there are other types that would work, although your requirement of 3" is pretty tight. Other members that use them will be able to advise you on the best one. When we bought our new tandem, we built it up w/o a suspension seatpost. My wife actually likes the non-suspension post better. Regarding carbon vs. aluminium or steel non-suspension seatposts...I have tried both. My wife doesn't notices a little more damping with our carbon post, but she has no real preference. Maybe your LBS will let you try a few seatposts out before you buy one. Hope this helps.
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Old 02-09-09, 12:15 PM   #3
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In my experience, I've found no difference in the ride quality between carbon and aluminum seatposts.

Moreover, even if there is any theoretical dampening benefit to a CF seatpost, the less the post is extended, the less of an effect. Thus, with only 3" of post extending, I think it is very unlikely that she would notice any difference in ride quality between cf and al.

5lbs less tire pressure would have a dramatically more noticeable effect on ride comfort.
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Old 02-09-09, 01:06 PM   #4
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Another possible solution if stoker wants/needs some sort of cushioning back there is to buy a saddle with springs. Brooks, among others, offers several models.
A wider rear tire can also help; and as Merlin X-tralite suggests: a bit less air pressure.
Stoker Kay has ridden 34+ years on our tandem(s) without any type of suspension seat post.
Pedal on TWOgether!
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Old 02-09-09, 04:59 PM   #5
PMK
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If I read your original post correct, it sounds as if the seatpost is set to high on account of the taper.

You might see where the stoker stem sets and may possibly be able to move the seatposts from front to rear.

The Speedster we had was real smooth, ride it a bit before committing to a suspension seatpost.

PK
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Old 02-10-09, 08:21 AM   #6
duppie
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All,
Thanks for your replies. Given that people do not find that a carbon seatpost provides significant better damping, we decided to go for an Alloy seatpost. Mrs. Duppie is OK with it and I find them online for $20 + shipping

Separate question: The diameter of a Co-motion stoker seatpost is 29.8 mm, correct? Right now the stoker seatpost is 29.4 mm and the captain's, which is original, is 29.8. Btw, this is not the cause of the seatpost sliding down.
Thanks, Duppie
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Old 02-10-09, 08:37 AM   #7
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Yes, 29.8 on my 2006 Co-Motion.
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Old 02-10-09, 10:19 AM   #8
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We put a Specialized Pave CF seatpost with the Zertz insert on for my wife in our Speedsteer. It has great dampening abilities but doesn't change your seat or knee position as do suspension posts. We briefly tried the S-Works model with a smaller Zertz fitting and different design but went back to the original per her request. It's a standard 27.2 and we simply use an aluminum sleeve adaptor.

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