Your take on Mcfk seatpost & seat-clamp?

Discuss light weight issues concerning road bikes & parts.
Limbo
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by Limbo

First of all, everything stated here is brand new, no pre-owned condition.

Of late, I have been experiencing slippage during each ride, despite effort to tighten the Mcfk seat-clamp with seatpost before each ride. [I am using torque wrench and are worried if I uses too much strength on the clamp, it will gives way.]
I weighed myself, and only gain few hundred grams. :oops: :oops:

[I don't even need to tighten each time for my other bike, and both bikes are usually in cruising speed.]

Have anyone using Mcfk 3K seatpost with its seat-clamp, and experienced similiar situation? (or not experiencing anything??)
What is your workaround solution? [buying another seatpost seem viable option, I keep them in mind]

bombertodd
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by bombertodd

I'd measure the seatpost to make sure it is the correct size (not just the correct number stamped on it). I had a 27.2 Easton Seatpost that measured 27.08mm and it kept slipping. I bought a Thomson and it measured in at 27.19mm and worked great. The seatpost needs to be the perfect size because the seatpost clamp needs to apply pressure over a larger area (flat all the way around). If the seatpost is too small or frame is too large the seatpost clamp will try to bend in grab around the top resulting in very little surface area to grab.

Good luck!

by Weenie


Limbo
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Joined: Sat Sep 03, 2005 12:14 pm
Location: Residing in Europe

by Limbo

I should have been more forthcoming about this problem, leaving much to speculate.
I have measured the bike frame and confirmed with its manufacturer, it is indeed 27.2mm in diameter.
Also I seek clarification from bikeshop before I placed the $$ to them for seatpost and clamp, so I am safe too.

Do you reckon I would need a shim?
Could it be the clamp was not tighten enough, leaving much room to slip?

This is dampening the christmas spirit.

bricky21
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by bricky21

Have you used assembly compound?
Image

bombertodd
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by bombertodd

Limbo wrote:I should have been more forthcoming about this problem, leaving much to speculate.
I have measured the bike frame and confirmed with its manufacturer, it is indeed 27.2mm in diameter.
Also I seek clarification from bikeshop before I placed the $$ to them for seatpost and clamp, so I am safe too.

Do you reckon I would need a shim?
Could it be the clamp was not tighten enough, leaving much room to slip?

This is dampening the christmas spirit.



I would measure both yourself if possible. Just because it says 27.2mm doesn't mean that it is. Manufacturing defects can occur and I'm pretty sure the bike shop didn't measure the post to ensure it's accuracy. They usually just look at what's labeled and ship.

Most clamps are 6-8nm in torque from what I've seen. You bike should have a recommended torque for the seatpost clamp and it should be plenty of force. I don't think tightening it is an issue, it doesn't take a ton of torque to keep the seatpost tight.

I've seen people with the same issue use a soda can to make a shim. It would be a cheap way to try it out. It would be best if you could try another post to ensure it is specific to your new post.


Oh and carbon assembly paste does not prevent things from slipping. It prevents carbon from galvanic corrosion. It may help slow down the slipping but it is not something I would rely on.

Oswald
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by Oswald

My BMC frame says 5nm and setting it at 5nm with a torque wrench left a serious clamping mark in the BMC seatpost :'( So I only use 4nm now in combination with the Tacx paste. I also wrapped a bit of tape around the post just above the clamp and it doesn't slip at all.

So it really depends on frame.

lannes
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Joined: Sat Nov 10, 2007 9:51 pm

by lannes

bricky21 wrote:Have you used assembly compound?
Image


+1 I definitely try some carbon assembly paste, it will increase the friction between the seat post and seat tube allowing you to use less force on the clamp.

Tacx Carbon Assembly Compound, FSA Installation Compound and Finish Line Fiber Grip are good products

The FSA comes in small packs, which is probably more than you need for a seatpost/ seat tube and stem/ handle bar interfaces.

http://www.trisports.com/fsa-installati ... paste.html

bricky21
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by bricky21

bombertodd wrote:Oh and carbon assembly paste does not prevent things from slipping. It prevents carbon from galvanic corrosion. It may help slow down the slipping but it is not something I would rely on.

Image
Thats some deceptive advertising then I guess. Lots of people use some sort of Carbon Assembly Compound to keep there parts from slipping.

Some carbon handlebars even come with it. I just assumed that it was because people were over tightening their bars to keep them from slipping :noidea: I was never aware that anodized stems corroding away from being in contact with clear coated carbon fiber was a real concern.

bricky21
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by bricky21

The seat clamp may also be the problem. I've not had good luck with WW carbon fiber seat clamps.

bombertodd
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by bombertodd

bricky21 wrote:Thats some deceptive advertising then I guess. Lots of people use some sort of Carbon Assembly Compound to keep there parts from slipping.



I too use carbon assembly paste (actually the same exact stuff in your picture) when the manufacturer calls for it. However I don't think it should be relied upon to hold things together. In my same experience as the OP with one of my bikes I tried all the way up to 12nm of torque and carbon paste out of sheer frustration. It just made the post slide down slower. I don't doubt that the paste will lower torque requirements in a mechanically sound setup, but that is most likely the issue, it's not mechanically sound. Unfortunately parts have tolerances. It is possible that the post is at the smallest end of its tolerance and the frame is the highest end of its tolerance. This leaves a too large of gap between seat post and frame. I don't know what the tolerances of each item are but I suspect that it is the issue, or one of the pieces is too far out (past tolerance) and not caught by quality control. I don't know how tight the seatpost/seat tube tolerances need to be to keep the post up either. But it is a simple system. When two parts seem to be the right sizes it doesn't take a lot of torque to keep the seatpost from slipping.

I still think the best method is measure the seatpost and inside the frame with a pair calipers and see what the difference is. Second I'd see if a friend has another seat post you could try and see if it stays up. If so I'd measure that seatpost to see if it differs from yours. If neither stays up, it could be a frame or seat clamp issue.

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Juanmoretime
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by Juanmoretime

When in doubt measure twice. Even if not in doubt measure twice. I have a Mcfk 31.6mm setback post in my Lynskey R320. I did use the Tacx carbon paste but my seat clamp of choice is the New Ultimate torqued to 4.5 nm. It has never slipped.
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RESIDENT GRUMPY OLD MAN.

Wcl4
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Joined: Thu Apr 12, 2012 4:33 am

by Wcl4

I have a mcfk clamp and used it with ax lightness post and it held at 4nm. I'd try putting a cloth tape around the post and then clamping personally. I agree you probably got two ends of the extreme which is creating tightening issues.

I once bought a brand new dogma 2 where the seatpost was too big for the seat tube and the bike shop didn't believe me when I told them it didn't fit until it was returned to them.

mdeth1313
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by mdeth1313

I'd still use the carbon paste to see if that solves the problem.
Speedplay is the devil!

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sugarkane
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by sugarkane

Sounds like something is not the right size and bombertodd you are kidding right.. It almost certainly does contain grit that does reduce the required torque to clamp items that are actually the right size in the first place... :noidea:


For the record I have own and have installed a number of trouble free mcfk seat posts

bombertodd
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by bombertodd

sugarkane wrote:Sounds like something is not the right size and bombertodd you are kidding right.. It almost certainly does contain grit that does reduce the required torque to clamp items that are actually the right size in the first place... :noidea:


I think me words above might be confusing. If the post is slipping I don't believe using carbon paste will magically make it go away. I use carbon paste (Finishline to be exact) and I do believe less torque is required when using it because of the grit. So if the seatpost will stay put with a given amount of torque the carbon paste will allow it to stay put with a little less torque (good for long term use of WW clamps and posts). But what I meant above is that if a post is slipping with max torque (per bike/clamp) adding carbon paste will not fix the slipping issue. There is plenty of torque which leads to a surface area mating issue. Something is not right (frame, clamp, post).

For the record I have own and have installed a number of trouble free mcfk seat posts


I'm sure these are good posts but even the best of companies can have manufacturing defects such as being too small of a diameter. Or it could be the frame. It's hard to diagnose over the internet, but a pair of calipers should be able to eliminate some of the variables.

by Weenie


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