Overtightened clamp on carbon seatpost – bugger

So I treated myself to a new carbon seatpost for my road bike. Cue an hour of grunting and sweating last night trying to get the old one out (been in there 4+ years), popped the new one in with a little silicon grease (didn’t have any of that carbon paste stuff), jobs a good un.

Commute into work this morning, plenty of tinkering stops to get the position just right. Didn’t bother bringing torque wrench with me as figured I’d get it right then check the torque later when I get home.

Go to work, gave it the once over to make sure nothing had slipped, noticed a crease in the post. Fu**ity ****, overtightened the collar and pinched the post. Not sure it’s completely split but doesn’t look great.

So – what can I do? I can’t afford another one so will probably just ride on this until it breaks, and hope it’s not a sudden failure involving carbon fibre splinters in the nether regions.

I could re-fit the old one as it’s perfectly OK – swapped as it was layback and new one is inline – but riding position will be back to OK but not great.

Any thoughts on how long I might be able to ride on it? It’s not like it’s MTB bars and going to be getting a lot of stresses and strains with the potential for a nasty failure.

Don’t silicone grease and carbon paste have completely opposite functions? Rather you than me though. I suppose it might be OK, but a seatpost snapping during a 40 MPH descent isn’t something I think I’d enjoy! Personally I wouldn’t risk it.

It’s not like it’s MTB bars and going to be getting a lot of stresses and strains with the potential for a nasty failure.

it will be getting lots of stresses and strains and failure could be fairly nasty.

it’s your choice but I wouldn;t ride it.

A seat post snapping at 20mph on a road bike is like falling off a roof without warning.

Do you feel lucky?

Don’t silicone grease and carbon paste have completely opposite functions?

That’s just what I was thinking as I was smearing it on, but it was after 11pm on a school night.

Thanks for the replies folks, just what I was expecting really despite hoping for someone to tell me it’ll be fine!

I’m fine with you riding it, I wouldn’t myself though :p
As above, you’d have been better off using nothing until you got hold of some fibre paste, greasing it just means you need to apply even more torque to the clamp to grip it. Obviously hard to say if it’s terminal without pics but most carbon posts will have a clear coat lacquer and a cosmetic weave top layer of carbon so it might just be one/both of those that’s damaged (although even then I guess it could create a weak point leading to an eventual failure).

if you ride on it, can you film it and post the results?

sounds like you’ve knackered it now (impressive you’ve managed to tighten it up so much that it’s split the post – what seat clamp/frame you got?), but apart from grease encouraging things to slip, it can also affect the resin/laquer used on some carbon components and causes it to swell… meaning your post wouldn’t move after a while anyway.

Well, I’m not sure it’s actually split the post – I need to wait until I get it home for a post mortem. As you say, it could just be the lacquer and top weave.

Storck Scenario 1.1 with a Storck clamp.

Sounds like an expensive lesson 🙁

I’d check the frame pretty carefully to – you’ll have compressed the top of the seat tube a fair amount in order to put that much force on the post 🙁

I had this on the stock carbon post on my roubaix. Kept slipping down, so one day i gingerly tightened it up until i heard a bit of a cracking noise, thought ‘oh bugger’ & undid it half a turn. Then went for a ride & guess what, still slipping. I then turned the seat collar so that the split in the clamp was at the opposite side to the split in the seat tube & tightened it up a bit more, no cracking but post still chuffin slipped.
In the end i just moved my rear light bracket down to it sat right on top of the seat clamp & it’s been fine ever since.

Thanks mos, that’s the kind of response I was hoping for! How big is/was the split?

I’ve mailed FSA also, telling them what an idiot I am and asking for advice (while secretly hoping they’ll take pity on me and offer to replace it 🙂 )

I need to wait until I get it home for a post mortem.

Genius 😀

So you managed to buy a post but no paste, and then fitted it for a test on your commute intending to tighten it without a torque wrench… Not a lot to add really 🙄

Not a lot to add really

Clearly. I’m aware of the stupidity of my actions, I’m asking for advice/opinions on the result of these actions.

silicone grease shouldn’t affect the resin. But it will lubricate it obviously.

tbh it will probably be fine. If worried I would get a saddle with a higher height (or some slightly lower pedals/shoes) so you can drop the seat post 5-10mm.

Bet you those 45grams or whatever it is you saved was worth it…

How much grunt did you give it anyway when tightening? I remember once putting about 25Nm into mine after I stupidly blindly relied on a torque wrench and it didn’t go click at the 5Nm I’d set but the post didn’t crack and has been fine since (2 years later).

andyl – thanks. I might leave early and swing by the LBS to get them to look it over.

turtlehead – It wasn’t a weight saving exercise, I’d do better to just lose weight. I took off a carbon lay back post and replaced with a carbon inline to improve my position on the bike, but thanks for your helpful comment.

Fuzzy – not that much, or so I thought. I just pinched it up, and probably put less on it than I’ve done with other components when I’ve not had a torque wrench to hand.

send it to someone to blather the 45g of some glue and fabric back up the inside of the post…

Just a small crack in the surface, not all the way through.
That was 5 yrs ago & i weigh 16st.