Slipping Seat Post / Seatpost slip

As the title says!
My seatpost keeps slipping on my BJ because I can't tighten up the binder tight enough.
I have snapped two binders already and now on my third, (some dodgy looking thing!)
But my big concern is I am going to snap the the ears on the seat tube because of the amount I have too tighten the bolt.
The seat post i am using is the right size (27.2).
Any ideas?

are you sure the seatpost is a 27.2, it sounds like it isn't????
that is what i would put it down too. if it is, then fuck knows.

first step surely it is to try another 27.2 seatpost...?

If the seatpin is 27.2, then clean the pin and the inside of seat tube with petrol or white spirit.
If it's 27.2 and that doesn't work, then the seat tube prob isn't 531 but older Columbus tubing and you need 27.4, But I doubt that.
M

Had same problem on my brand new BJ; bust the one hat came fitted, and a spanking new Campy one from Condor before the £2 decathlon one let me tighten it enough to hold post in place. Even more of a pisser cos i had to get tube reamed to even get a 27.2 in here in the first place.

I've had this on a steel frame where the slot that's cut into the top of the seat-tube wasn't deep enough. You could get the hacksaw out and lengthen the slot by 5 or 10mm, which would help the tube compress against your seatpost enough; if that's the issue.

And as usual, make sure the bolt is greased - threads, and under the bolt head.

Thanks for the replies everyone.
It is defiantly a 27.2 post and I have tried two other posts too.
I think it is o.k for the time being with the big ugly ass bolt I have in it atm until I can figure out what to do.
To make sure it don't slip, I have cleaned the post and put a mark to see if it starts slipping.

Now my other problem is...lol...anyone know why there is slack in my hubs? No up and down play, just back slack, if that makes sense?

Hairspray ... clean the grease off the seat pin and inside of the seat tube with acetone, or some degreaser, mark the correct height, spray hairspray on the seat pin, tighten seat bolt, and .... see if it works ... it did for me in a similar situation.

Buy one can of larger and a small tub of assembly paste.

Make a single layer shim from a neatly cut rectangle of beer can material (one or less wrap around the post).

Lightly 'key' (sand the surface very lightly to increase friction) both the inside and outside of the the shim - also key the part of the post that is hidden in your frame - and you could even try a light keying of the inside of the seat tube.

Now get your assembly paste.

Put a thin (must be thin!) layer of assembly paste on both the inside and outside of the shim and assemble the shim/post/clamp to taste.

Cheaper beer cans (supermarket own brand) = thinner alloy, more expensive booze = thicker cans. By the sound of it thinner may be better.
(Do not use Kronenberg - steel not alloy, will rust - Do not use Stella - embossed can causes tolerance problems)

I have just done this exact fucking thing, WAC. Anyone know the shop most likely to do a replacement, between Chiswick and say, South Beers?
I'm thinking Putney Cycles. Really looking forward to riding several miles out of the saddle in the rain.

PUtney cycles had one for me a few months back.. it took a lot of looking though!

If not them then Holdsworth, but they may be closed now..

There's also a little place on Dawes Road or Evan's in North End Road (I think?)/Clapham... BC are only open 'til 6 tonight if you don't have any luck elsewhere...

Thanks guys!

I had the same problem when building my bike up not long ago, my seat tube seemed to be between 2 sizes so had to use a coke can shim in the end, although its still not quite right. Although the post holds, it can twist slightly, therefore I may buy a can of plack spray paint just to up the thickness a little, tho Ive allready snapped my campag seat bolt :(

This is exactly what I did on my mountain bike beater when I couldn't be arsed to buy the right size post. I used a coke can which worked great.

Buy one can of larger and a small tub of assembly paste.

Make a single layer shim from a neatly cut rectangle of beer can material (one or less wrap around the post).

Lightly 'key' (sand the surface very lightly to increase friction) both the inside and outside of the the shim - also key the part of the post that is hidden in your frame - and you could even try a light keying of the inside of the seat tube.

Now get your assembly paste.

Put a thin (must be thin!) layer of assembly paste on both the inside and outside of the shim and assemble the shim/post/clamp to taste.

Cheaper beer cans (supermarket own brand) = thinner alloy, more expensive booze = thicker cans. By the sound of it thinner may be better.
(Do not use Kronenberg - steel not alloy, will rust - Do not use Stella - embossed can causes tolerance problems)

shim?

Shim

Also this site will help you.

Hello there,

I have this problem with my fillmore, which is slowly doing my head in:

The seatpost slowly slowly keeps slipping down, no matter how much tighten the clamp. The bike is a year old, and it always happened, but lately it's just happening faster for some reason? Before I had to adjust the seatpost every week or so. Now after a 10 mile ride the thing moved down like 3.5 - 4 cm.
I already changed have the clamp. I even tightened the thing up that the screw snapped. Tuesday I got myself another clamp (more expensive one, seemed more solid) but the thing still moves down, even thoiugh it seems to sit rock solid, can't move it with bare hands.

Any ideas?

https://www.londonfgss.com/thread2357.html

and/or replace the seatpost clamp. I had the same problem and it was resolved by getting a better clamp.

wrong sized seatpost? (try a shim)

Well, it's the one that came with the bike. The clamp is an 11 pound one, and the 3rd I tried, from various shops. I'm a bit at a loss with this. I think I still have warranty on it from Brixton Cycles, but the problem is that they're always closed when I have time :(

Evans really the only shop that has its doors open a bit later? I'd prefer a decent shop!

Coke can shim.

tim tam slam

sounds as if they stuck a 27mm, in a 27.2mm hole