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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 01-19-09, 11:22 AM   #1
swc7916
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Suspension Seatpost Failure

This was an unexpected failure: Karen and I had just finished our ride on Saturday and as she was dismounting the bike the stoker's seat fell off! It turns out that the head of the seatpost is just pressed onto the post and it had worked itself off. It's a good thing we were at the end of the ride instead of being stranded in the middle. What scares me most is what could have happened if it occurred while we were riding.

This was a Tamer PivotPlus. We got it with our Rodriguez tandem and it has about 2,500 miles on it. I took the post back to R+E and since they didn't have another Tamer in 25.4mm, Scott gave me a Crane Creek ThudBuster to try. I hope that Karen likes the ThudBuster because it looks more trouble-free to me: The base of the head is a machined part of the post - it is not pressed on - and there are fewer moving parts. I have heard of cases where the elastomer insert ruptured, but I hope that sort of failure would not be catastrophic. The Tamer design is always under spring tension and depends on a friction fit to keep the head on.

Last edited by swc7916; 03-18-09 at 08:42 AM.
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Old 01-19-09, 11:27 AM   #2
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While we do not use a suspension seatpost for stoker, we have test ridden several. The Thudbuster (in my stoker's opinion) was the best after the Allsop c/f beam.
Someone can always make something cheaper and the Tamer failure proves that point.
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Old 01-19-09, 11:32 AM   #3
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Someone can always make something cheaper and the Tamer failure proves that point.
I don't know that the Tamer is cheaper - it's just a different design. My concern - now that I know about it - is that the spring inside the seatpost pushes up against the suspension mechanism, which is a press-fit on the seatpost.
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Old 01-19-09, 04:54 PM   #4
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While we do not use a suspension seatpost for stoker, we have test ridden several. The Thudbuster (in my stoker's opinion) was the best after the Allsop c/f beam.
Someone can always make something cheaper and the Tamer failure proves that point.
Interesting! My stoker hated the Thudbuster because it moved down and back, effectively moving her away from from the pedals with each depression, rather than the Tamer which just goes down. So the Tamer is on it's 7th year.
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Old 01-19-09, 05:35 PM   #5
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I don't know. The Tamer Pivot plus that we have has a paralelogram shape that moves the seat back once it is depressed as to not to drastically change the distance from the seat to the pedals. Ours failed, collapsed, after 15K miles
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Old 01-20-09, 07:29 AM   #6
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Originally Posted by swc7916 View Post
I hope that Karen likes the ThudBuster because it looks more trouble-free to me: The base of the head is a machined part of the post - it is not pressed on - and there are fewer moving parts. I have heard of cases where the elastomer insert ruptured, but I hope that sort of failure would not be catastrophic. The Tamer design is always under spring tension and depends on a friction fit to keep the head on.
FWIW: the Thudbuster's head used to be pressed on. Several years back they switched to the machined head because too may Thudbusters lost their head

Friends of us have had a telescopic Tamer fail some years ago: the 'rod' that actually carries the saddle snapped.
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Old 01-20-09, 08:47 AM   #7
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We had continual problems with Tamer seatposts and gave up on them. When we contacted Tamer their response was "you are the only ones that have had that problem."

Sheldon and Martha
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Old 01-20-09, 08:56 AM   #8
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We have a Thudbuster and my stoker loves it. It sure looks like a solid design.
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Old 01-20-09, 12:18 PM   #9
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Had a thudbuster on since 2004- and it is an offroad tandem. No problems and I wouldn't use anything else.
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Old 01-20-09, 09:54 PM   #10
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Stoker Malkin says +1 on the Thudbuster. She also uses a much stiffer insert than suggested for her weight so the thing doesn't bounce at all--it just provides firm damping for the hard hits (which, of course never happen because I'm such a competent captain...)

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Old 01-21-09, 09:52 AM   #11
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Originally Posted by antiquepedaler View Post
Interesting! My stoker hated the Thudbuster because it moved down and back, effectively moving her away from from the pedals with each depression, rather than the Tamer which just goes down. So the Tamer is on it's 7th year.
The Tamer PivotPlus is a parallogram design similar to the the ThudBuster; it's just that the spring design is different. The Tamer uses a spring and a piston inside the seatpost whereas the Thudbuster uses an elastomer "puck" inside the parallogram mechanism. According to my stoker, the Thudbuster bounces more and is harder on her sitbones; the Tamer "floats" and the bumps don't hit her as hard. I'm guessing that the force required to compress the Thudbuster is non-linear - that is, it gets stiffer the more it's compressed - whereas the spring in the Tamer exerts a more constant force. It also appears to me that the Tamer has more travel.
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Old 01-21-09, 10:16 AM   #12
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What we like about the Tamer is the ability to set the force required for actuation. Properly set for the weight of the ridder, the seat does not float. It only actuates when a critical force is reached.
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Old 01-21-09, 05:27 PM   #13
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What we like about the Tamer is the ability to set the force required for actuation. Properly set for the weight of the ridder, the seat does not float. It only actuates when a critical force is reached.
Our Thudbuster LT has an adjustment for pre-loading which sets the activation force. It also came with a selection of inserts that can be mixed or matched for six firmness adjustments. There are even more inserts available for an extra light person.

I understand the Thudbuster ST is much more limited.

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Old 01-22-09, 05:32 AM   #14
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Stoker loves her thudbuster ST.

She used to hate the original suspension post as it kept "bouncing" when we put the power on
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Old 01-27-09, 08:21 PM   #15
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My stoker has used the PivotPlus for many years and is very happy with it once it is adjusted properly. The pins wear out after a while. I contacted Tamer - they had me ship it back and they replaced the pins for a reasonable charge. It's been working fine ever since (> 1 year).
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