Seatpost problems

pholt89

Hi
I recently replaced the stock alloy post that came with my planet x frame with an Easton EC70 carbon post.
When I first fitted it it didn't seem to be as snug a fit as the previous one and even after applying fiber grip I am still having problems with it gradually slipping down when I'm riding.
I have checked and both seatpost and frame say they are 31.6mm however before I do up the seatclamp there is even a tiny bit of play between the post and the tube.
Has anyone else had a similar problem or have any suggestions for how to fix it?
Thanks
Phil

Burt25

You may be able to get a seat post shim that will do the job for you- I think you would need about 1.5mm of space between the post and down tube when loose for that to work.

bernithebiker

Piece of paper round the post, thin or thick bit depending how big the gap is.

You won't see the paper as it will be inside the frame.

pholt89

Hi thanks for the replies.
Definitely not as much as 1.5mm of space between the frame and post, it is a tiny amount of play when the bolt is undone but enough to lead it to slip when done up.
Will try the piece of paper tomorrow and see if it works.
Its just so annoying that they are supposedly the same size and yet aren't.

Burt25

You, might be better wrapping some insulating tape round the post as paper will deteriorate when it inevitably gets wet

desweller

Burt25 wrote:

You, might be better wrapping some insulating tape round the post as paper will deteriorate when it inevitably gets wet

I wouldn't do this. After a year or so of being in there the tape will break down into a gungy horrible sticky mess. Ugh.

sungod

try some carbon assembly paste, tacx or the grittier one from finish line

pholt89

Thanks for the suggestions.
Still not sure what I'm going to try yet.
Sungod: I have already tried finish line assembly paste and it helped but still just a very gradual slip down (aprox 5mm over a 30 mile ride)

freezing77

Coke can shim.

sungod

if there's noticeable play between post and seat tube then probably the the seat tube is out of spec.

if it's too small for a shim, then to increase the od of the post slightly, you could try this...

degrease it fully, start with white spirit, then remove any remaining residue with acetone or isopropyl alchohol

mix up some epoxy, you only need a drop but to ensure correct mix ratio you'll need to do more, use a piece of lint free cloth to wipe a very thin layer onto the area of post where it will be clamped by the seat tube

let it dry *completely*

try post, see if it still slips, there'll still be traces of assembly post in the seat tube

if the layer is too thick you can reduce it with fine abrasive, too thin and you can always repeat the process to build up thickness

pholt89

Thanks again for all the help I may try the epoxy method as a last resort. Does it require a specific kind of epoxy?
Do you think it is worth contacting Planet x about it before attempting it or will they just say its not their problem?

gaddster

How about some clear nail varnish on the post if you don't fancy the epoxy route?

desweller

I would think very carefully before trying to skim a layer of epoxy onto your seatpost. You'll have a hell of a job getting it round; the seat post will have lots of high spots unless you're very, very skilled. And once it's on there you'll not get it off again.

I would go down the shim route myself.

sungod

i'm suggesting wiping the post with a cloth that's 'damp' with epoxy, not skimming a layer on like plaster which i agree would be a nightmare, given the degree of clearance the op says exists, which seems to be too small to shim, it's a reasonable approach, also easy enough to buff off if too much is applied, i've done similar on non bike parts

op:
unless it's a brand new frame and you can demonstrate it is out of spec i don't think planet x could/would do anything about it

if you've got some (accurate...) calipers you can measure both posts, but aside from knowing the diameters it probably won't help get a resolution

btw another possibility is that the clamp is no good, depending on the frame you may be able to change it

any general purpose epoxy should be ok, you could use varnish etc. but i think it will be more likely to flake off or be abraded, and may be more susceptible to sticking the post into the seat tube if it gets exposed to a solvent when you clean the bike

Ouija

You may have a mislabelled seatpost. It might be the 30.9mm version of the EC70 mislabelled as the 31.6mm version (0.7mm difference). Having worked in factories, i've seen stuff like this slip past quality control way too often.

dgunthor

^^^ good point

get it measured with calipers before you try any 'fixes'