# Tarmac seatpost clamp...why backwards?



## skygodmatt (May 24, 2005)

I have been racing with many riders on their Tarmac SL's. Seems as though they are having problems with seat post slippage. 

What I noticed is the Tarmac seat post clamp has the pinch bolt placed on the opposite side of the split in the seat tube. Why did they do this? I rotated the clamp 180 degrees. This placed the bolt next to the split so when you tighten the bolt, it pinches together the gap in the tube. This works great...no more slippage.
Anyone know the reason why they designed it like this? Am I missing something?

I am sure this problem has come up before.


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## Stratmosphere (Feb 28, 2007)

I didn't ask. I just torque it down!


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## mh3 (Mar 8, 2006)

According to Specialized, placing the slots opposite each other, more evenly distributes the clamping force around the seat post, lessening the chance of the seatpost cracking and failing at the pinch point that's created. From a waranty standpoint, turning the clamp around could technically void your seatpost warranty. As far as slippage is concerned, the various carbon prep products from FSA, Tacx, and Ritchey do a great job of eliminating slippage without forcing you to push the limits of torque.


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## skygodmatt (May 24, 2005)

*Makes sense but....*

I can see that point. The only problem is I know two riders that mistakenly over-torqued their posts and they cracked them because they thought they were not tight enough due to the slippage. At the proper torque setting, checked with a snap-on wrench -- with the clamp lined up the standard way-- there has not been slippage yet. As a matter of fact, I've seen bike shops reverse the clamp too. I have also been told by a specialized rep. that sometimes minute post diameter differences can be a culprit and they replaced a buddy's post with no problems with the new one in the Specialized clamping way. Another buddy put a thin layer of masking tape around the post. It hasn't slipped yet due to the rough texture and fine thickness of the tape.


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## NewTrekRoadie (Sep 13, 2004)

The carbon prep products mh3 referenced above worked like a charm for me. They have tiny beads in the goup that prevent slippage when putting a carbon post in a carbon frame. Since I put just a bit on my post it hasn't slipped a single bit. A specialized rep actually recommended using the Tacx carbon prep product....


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## skygodmatt (May 24, 2005)

*sounds good*



NewTrekRoadie said:


> The carbon prep products mh3 referenced above worked like a charm for me. They have tiny beads in the goup that prevent slippage when putting a carbon post in a carbon frame. Since I put just a bit on my post it hasn't slipped a single bit. A specialized rep actually recommended using the Tacx carbon prep product....




Sweet...that's the ticket then.


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## Tugboat (Jul 17, 2006)

Crimping of the carbon by the pinch point is a common problem. I had a correctly torqued Deda Magic Stick literally snap off in my hand when I lifted my bike of a rack (not a Specialized). When examined, the post showed clear signs of damge to the carbon at that point. Has happened to a number of other riders I know as well. Reversing the clamp works in eliminating the problem and there's no way I'd ride a bike now with a carbon post where the clamp wasn't turned.


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## MaestroXC (Sep 15, 2005)

*Ditto*

The clamp slot should not be on the same side as the frame slot: bad things result.


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## roubaixowner (Sep 22, 2006)

I was having the same problem with my Roubaix and just put climbing chalk around the post and problem solved. Definitely a cheaper solution.


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## CtG (May 13, 2021)

It is not the clamp who bite into the post. The edges of the seat tube will. If you align the slit of the tube with the slit of the clamp the tendency of the edges will be to follow the easy resistance path which is a straight line and not a curved line. If the clamp is reversed, using a relative thick non deformable clamp, the edges of the tube will follow the radius and not crimp into the post. Of course the effort of tightening will be substantial cause now the clamp act to the whole section of the tube and not just to the edges. And mainly it have to compensate the friction between the clamp and tube till the circumference of the tube is tight deformed over the post. I wonder if a regular 6 Nm collar can ensure this ?


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