Fitting new carbon seatpost
I have purchased a new 31.6 mm carbon (Cinelli Ram) seatpost, for a carbon frame bike. The existing seatpost is a 31.6 mm alloy model, and it slips in and out easily without even needing to twist it. The carbon post goes in about an inch, and sticks. I haven't forced it yet, and the Cinelli instruction leaflet warns against both greasing the post or twisting it to go in. I really don't want to ruin the seatpost, or damage the frame. Worst of all would be a jammed seatpost. Despite the warnings, I think I've got to use some sort of lubricant. Can anyone help, please?
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Thanks, Redddraggon, but it's squeaky clean. I tested this with a piece of clean white cloth tied round a stick, and there is only a trace of what I think is carbon dust. I have now written to Mr Cinelli to ask his advice.0
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you could loosen the seat clamp so its really 100% loose - some people use a hairdryer to expand things a bit - your call
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Logically the seat post sounds as if it is slightly over size, or maybe not paralell. I would measure it with a micrometer if I was you. It would be good to compare it to the old one too.0
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Well, it can go in after all.
I applied a tiny piece of (Michelin all-purpose) grease to the bottom of the seatpost, spread it around the outside of the post and then wiped it off to leave a very, very thin film of grease - hardly noticeable. I had attached a saddle to get extra leverage, and with a bit of effort it went in. Once it got past the seat collar area (and I slipped the seat post collar up the post so it would not be a constricting factor) it was relatively easier to push all the way down. I can only guess that the very bottom of the seat post, by which I mean an inch or so, is fractionally bigger than the rest of the post. It does have some printing underneath the carbon lacquer, but would that make it thicker? It must be the seatpost: if the seat tube was too small, then the seatpost would encounter the same resistance all the way down. I'm sorry I don't have a micrometer (I spend all my money on exotic Italian seatposts, to match the Ram combo at the front end).
I think that the amount of grease is almost negligible, but I am aware that lots of previous threads have said "don't grease carbon seatposts"- which is why I didn't try this way first. Is this because it would make it slippy and hard to tighten, or is there some chemical reason that the carbon will degrade? All contributions welcome.0 -
Hi Brian,
Standard greases / lubs penetrate the carbon fibre layers and cause the material to expand. This can cause the seat post to get stuck in the frame (I found this out the hard way - cue an £80 repair bill from the LBS to chisel the stuck post).
You need a carbon specific grease like this :
Tacx Dynamic Assembly Compound Carbon
http://www.probikekit.com/display.php?code=A16370 -
I really appreciate the advice from Alloneword, which is worth so much compared with the unspecific warnings from the manufacturer. It seems the answer for my problem, and I have ordered a tub of carbon assembly compound tonight (Probike is out of stock, I have ordered from J E James) which at £10 is cheap compared with the consequences described above. I can hardly wait for delivery.
This episode has annoyed me a little. Why don't the manufacturer(s) be more helpful by including a small sachet of carbon assembly compound with their product - it would cost them about sixpence, and may save their customers from comitting irreparable damage to their bikes. I shall commend this to Mr Cinelli, who still hasn't replied to this paying customer's plea for help.
I shall post another note when the stuff has arrived and hopefully it will have worked.0 -
don't worry about it..
there is such widespread debate about grease / no grease with regard to carbon that there is a chance that both sides (or no-one) is right!
make it part of your routine maintenance to rotate the seatpost in the tube every once in a while - or remove it and clean it up - it'll be fine!0
