Seat Post - Help?

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Seat Post - Help?

Postby MaxBauer » Fri Jan 17, 2014 5:37 pm

Just wondering if anyone could shed some light on a slight issue I have

I'm looking to change my seat post to a carbon one so I measured the diameter of them with vernier calipers; 27.2mm diameter which seems relatively common on most bikes.
So I went and scored one on eBay however the diameter was smaller than 27.2mm despite clearly being marked the correct size. Dissapointed, I went and got another and again
they were smaller. Both are FSA items and relatively cheap so it doesn't bother me too much but where am I going wrong?

Any help would great!
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by BNA » Fri Jan 17, 2014 6:36 pm

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Re: Seat Post - Help?

Postby Duck! » Fri Jan 17, 2014 6:36 pm

How big is the discrepancy? If it's within a few 1/10s of a mm, then it will be fine.
I had a thought, but it got run over as it crossed my mind.
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Re: Seat Post - Help?

Postby ball bearing » Fri Jan 17, 2014 7:01 pm

Don't forget to apply some carbon assembly paste after you clean the seat tube with alcohol...

http://www.ebay.com.au/itm/FINISH-LINE- ... 5660711c36
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Re: Seat Post - Help?

Postby KGB » Fri Jan 17, 2014 8:27 pm

Yep, definitely NO GREASE on a carbon part like a seat post.

Waiting to hear how much smaller than 27.2 the posts are...
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Re: Seat Post - Help?

Postby ball bearing » Fri Jan 17, 2014 8:53 pm

Speaking of seat posts....I finished my new carbon bike today and the carbon seat post is creaking like anything. I will try turning the clamp around and using a torque wrench. Geeze it makes a lot of noise.
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Re: Seat Post - Help?

Postby Mulger bill » Fri Jan 17, 2014 9:35 pm

ball bearing wrote:...I will try turning the clamp around...

Ummm, wut?
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Re: Seat Post - Help?

Postby mitchy_ » Fri Jan 17, 2014 9:36 pm

ball bearing wrote:Speaking of seat posts....I finished my new carbon bike today and the carbon seat post is creaking like anything. I will try turning the clamp around and using a torque wrench. Geeze it makes a lot of noise.


Did you use carbon paste?
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Re: Seat Post - Help?

Postby ball bearing » Fri Jan 17, 2014 9:38 pm

mitchy_ wrote:
ball bearing wrote:Speaking of seat posts....I finished my new carbon bike today and the carbon seat post is creaking like anything. I will try turning the clamp around and using a torque wrench. Geeze it makes a lot of noise.


Did you use carbon paste?


Yes. I'm just heading to the workshop and get to the bottom of this creaking, I hope.
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Re: Seat Post - Help?

Postby MaxBauer » Fri Jan 17, 2014 11:59 pm

The FSA seat posts I have are a good few mm smaller and doesn't fit snug as I've already tried. I'm tempted to go with another brand and see how that goes but thanks for the heads up on the Fibre Grip stuff guys
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Re: Seat Post - Help?

Postby KGB » Sat Jan 18, 2014 11:57 am

A good few mm?!? Thats completely fked. Sounds like they could be ebay knock-offs, I'd be chasing a refund if I were you. Seatpost sizes vary in 0.2mm increments so "a few mm" too small is never going to cut it.
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Re: Seat Post - Help?

Postby ball bearing » Sat Jan 18, 2014 12:23 pm

I'll dig out my calipers to check the tolerances. My creaking seems to have settled down. I took the bike for it's first real ride this morning. Torque wench appears to have cured the annoying racket. 5Nm is a good amount of energy. I wouldn't be comfortable pushing it that far without the proper tools.
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Re: Seat Post - Help?

Postby trailgumby » Sat Jan 18, 2014 12:29 pm

From memory, 4.8Nm is the recommendation etched on the clamp on my Scalpel, so that sounds about right.
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Re: Seat Post - Help?

Postby MaxBauer » Sat Jan 18, 2014 3:22 pm

KGB wrote:A good few mm?!? Thats completely fked.


Yeh when I went to fit it, it's completely loose and it was for both of them! I can't refund now as it's awhile back and only got back to riding unfortunately.
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Re: Seat Post - Help?

Postby Mulger bill » Sat Jan 18, 2014 7:13 pm

With that sort of difference, it might be worth cutting a beer can up as a shim.
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Re: Seat Post - Help?

Postby KGB » Sat Jan 18, 2014 8:09 pm

I've done that before but this case sounds like its too much for the old coke can shim.
For those who look down on it as a solution - it was good enough for Greg LeMond's aerobars when he beat Fignon at the Tour!
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Re: Seat Post - Help?

Postby ball bearing » Sun Jan 19, 2014 10:36 am

trailgumby wrote:From memory, 4.8Nm is the recommendation etched on the clamp on my Scalpel, so that sounds about right.

Damn! The noise is back!!! Never had this problem before. The max torque is stated as being 6.5Nm. Maybe I'll increase it in stages till the creak croaks it.
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