Seat post keeps sliding down!

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rapid_donkey
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Seat post keeps sliding down!

Postby rapid_donkey » Thu Feb 21, 2013 19:43 pm

I have a Giant with the standard Giant connect seat post and QR clamp.
When I bought the bike it all worked fine.
Before xmas I bent the seat post with a dodgy landing and replaced it with another new Giant connect.
When I fitted it I put grease on the shaft to prevent it getting stuck in the frame. The seat post kept sliding down, so I have wiped away all the grease on the post, as much as I can out of the frame, and do the clamp up as tight as it physically goes. My seat still drops. Today I had to stop and adjust it 3 times on a 12 mile ride.
Im no bloater at 82 kg's. Anyone got any suggestions?

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nicklouse
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Re: Seat post keeps sliding down!

Postby nicklouse » Thu Feb 21, 2013 19:46 pm

it the seat post the same size?
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ilovedirt
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Re: Seat post keeps sliding down!

Postby ilovedirt » Thu Feb 21, 2013 19:54 pm

Strange, mine sometimes does that if I put too much grease on it, but stops if i wipe it off.
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MTB1997
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Re: Seat post keeps sliding down!

Postby MTB1997 » Thu Feb 21, 2013 20:12 pm

Perhaps definetly check if the new seatpost is the right size as this may be what's causing the seatpost to fall down?

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bennett_346
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Re: Seat post keeps sliding down!

Postby bennett_346 » Thu Feb 21, 2013 20:13 pm

Bad QR possibly, i used to have one that came with my bike that didn't clamp the post enough despite having to use a rediculous amount of force to close the lever. Replaced it for a good clamp and it grips fine now.

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Batmo
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Re: Seat post keeps sliding down!

Postby Batmo » Thu Feb 21, 2013 20:19 pm

I had this problem and replacing the clamp was the answer.

Of course, I am a bloater...
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rapid_donkey
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Re: Seat post keeps sliding down!

Postby rapid_donkey » Thu Feb 21, 2013 20:42 pm

The replacement seat post is the exact same item as I bent, same length and width.
It could be the seat clamp, just strange as it was working fine before.
What seat clamps to people rate?

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bennett_346
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Re: Seat post keeps sliding down!

Postby bennett_346 » Thu Feb 21, 2013 20:43 pm

I personally rate the Hope QR seatclamps, but i got mine for £5 in halfords, not sure i'd pay the full RRP :lol:

2x10
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Re: Seat post keeps sliding down!

Postby 2x10 » Thu Feb 21, 2013 22:54 pm

I put a turn of electrical tape around mine, problem sorted, and Im super bloater!

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The Spiderman
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Re: Seat post keeps sliding down!

Postby The Spiderman » Fri Feb 22, 2013 06:34 am

When I had this problem with my XTC a cheap m part bolt up clamp cured it.


BigAirNig
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Re: Seat post keeps sliding down!

Postby BigAirNig » Fri Feb 22, 2013 10:20 am

I use a HOPE QR and it holds my Thomson post fine .... never slipped ....
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rapid_donkey
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Re: Seat post keeps sliding down!

Postby rapid_donkey » Tue Mar 05, 2013 21:03 pm

Quick update on this thread as its become a really annoying problem!!

I tried to put a small amount of tape around my seat post, but it never stayed on when I fed the post back into the bike.

I have disassembled the Giant QR clamp, fully cleaned and regreased it, still made no difference.

As this has all only occured since I fitted the new Giant seatpost, Im hoping it is that. When the seatpost is in the frame, there is a bit of lateral movement without the seat clamp tightened.
Im going to take the post into work tomorrow and measure it with some digital calipers.

I really hope it is the post, otherwise could I have possibly stretched my frame with the dodgy landing that bent my original post?

I did buy the post from an eBay seller for £15. Depending on tomorrows measurements, Im wondering if it is genuine...

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WindyG
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Re: Seat post keeps sliding down!

Postby WindyG » Tue Mar 05, 2013 21:20 pm

I would try a standard bolt clamp first rather than the QR one.

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Giraffoto
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Re: Seat post keeps sliding down!

Postby Giraffoto » Wed Mar 06, 2013 08:02 am

rapid_donkey wrote: When the seatpost is in the frame, there is a bit of lateral movement without the seat clamp tightened.
Im going to take the post into work tomorrow and measure it with some digital calipers.


I strongly suspect you'll find it's the wrong size. There should be zero lateral movement but smooth up-and-down movement when the clamp's not done up. Also you could have got one for less than £15 and the right size from several places - On-One and Superstar spring to mind
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ljs1977
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Re: Seat post keeps sliding down!

Postby ljs1977 » Wed Mar 06, 2013 08:23 am

Degrease the post and the bike and the clamp.

Apply carbon assembly paste to post in lieu of grease.

Report back.

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.blitz
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Re: Seat post keeps sliding down!

Postby .blitz » Wed Mar 06, 2013 08:48 am

As above carbon assembly paste: http://www.wiggle.co.uk/ritchey-liquid-torque/

There's enough in that sachet for several seatposts/bars

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rapid_donkey
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Re: Seat post keeps sliding down!

Postby rapid_donkey » Wed Mar 06, 2013 10:56 am

It was suggested by my LBS that I try some fiber paste on the seat post, but its an option I would like to use only if it comes to it.

So, this morning I measured the width of my seatpost with digital calipers.
It is supposed to be 30.9. Along the length of the post, I am measuring between 30.79 to 30.81. I am guessing that could make a difference. It is 30.8 where my seat post sits in the clamp on the frame.

I have now ordered another Giant Connect seatpost but from a Giant dealer this time. It was still only £20.
I went for the Giant one as it comes in 375mm length, instead of getting a 400mm and cutting it down.
However, if the new seatpost also measures short on width, I will be sending it back and getting an aftermarket post.

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stubs
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Re: Seat post keeps sliding down!

Postby stubs » Wed Mar 06, 2013 11:09 am

Did you measure the frame internal diameter sometimes they can be reamed oversize by mistake. I would just make a shim out of a coke can.
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Chinley Churner
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Re: Seat post keeps sliding down!

Postby Chinley Churner » Fri Mar 08, 2013 14:29 pm

+1 for assembly paste... no brainer


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