arod

I have a Merida Big Nine CF XT mtb.

Over the last couple of weeks the seat has started twisting around a bit. It appears that this is due to the connection that allows the seat to screw into the top the seat post being loose. I've highlighted this using the arrow in the below picture.

Based on the feel of how this connection moves, it appears like the connection at the top of the seat post might be clamped to actual seat post and that there are 'teeth' as part of the connection. When it moves it feel like it is jumping from one tooth to the other.

For reference the seat post is a Merida Carbon H SBO 27.2mm.

Is there any way to fix this or is it time to look at a new seat post?

Thanks

dsbrantjr

If there is not a bolt holding the clamp to the post or a threaded connection it is likely a press-fit with knurling which accounts for the notchiness. If this is the case I would advise applying some wicking-grade adhesive into the joint. I have used this method to stop a shimmed handlebar from creaking which is a similar application.

fietsbob

Bike under a year old? new bike, 1st owner? warranty claim thru dealer..



Or Time to go shopping? ... get a forged and machined single piece aluminum seatpost , there are many.. buy Quality.. Thomson?

if 1 piece, then there will not be any separate pieces.. head and tube..

Or, you must take off the head entirely and then clean it and re apply fresh epoxy..
On other posts running a pin thru it has been done.. to further join 2 parts..


IDK who Merida buys seat posts from, they own a big chunk of one of their client companies Specialized.

SBI sends bike designs Merida builds for them.. and other brands.. and exports them..





....

Kontact

Stop riding this post!

You can't reliably fix this in a way that will assure you aren't grievously hurt if it fails.


I would try to get it warrantied, but if not replace it. It is a common enough zero set back post.

dabac

The saddle clamp loose in the tube of the seat post?
I’ve tried fixing a few.
Never managed a good fix w/o working the clamp loose entirely first.
Never tried it on a CF post.
Might do if I got the top out with both parts in good condition.

Andrew R Stewart 

First step might be getting a replacement post so you can continue to ride while trying to fix the old. There's a lot of very low cost posts out there. I doubt you or the bike will be able to tell how much it cost when you're riding.


As dabac suggested completely pulling out the clamp top/plug will likely give you the best chance to clean up the mating surfaces and try rebonding the head back in. Make an indexing mark on both the shaft and head to allow for realigning at the same rotational position. Don't be surprised if this doesn't work. Andy

Kontact

A very painful surprise.

Andrew R Stewart 

Agreed although far less likely to be a fall down then a bar, stem, pedal spindle breakage Andy

Kontact

I suppose it depends if you manage to catch yourself before your butt lands on the rear wheel and you manage to hang onto the handlebar without putting the shaft in your abdomen. If it goes, it will go when you hit a bump sitting up.

Obviously, I think trying to re-engineer a bonded post is a questionable concept.

phughes

If it were me, I would but a new seat post. If the seat post wasn't too old, I would be inclined to reach out to the company for a possible warranty claim. You may be a able to bond it together, I am very practiced at reparing things like this, but I still would most likely buy a new post.

Ghrumpy

True. But you don't have to fall down to get injured. A friend of mine once broke an aluminum post and it put a nice deep gash in his thigh. CFRP would probably leave a gash and splinters.

Andrew R Stewart 

I have a friend who peed blood after hitting his saddle really hard... So no need to even break anything. Andy

ThermionicScott 

And that's if you're lucky enough to catch the broken post with your leg, rather than where it usually points.