tough_boots

Hi all,
I have a seatpost that keeps slipping. I’ve tried liquid torque and I’ve replaced the old binder bolt but it’s still an issue. It’s better than it was but still dropping slightly. The new binder bolt is the same length as the old one which I believe was the original for the frame and is 19mm. I just ordered a 16mm to see if that might do it but I’m also thinking I’ll throw some blue locktite on the threads. Is there any reason I shouldn’t use locktite on minor components like this?

Dsprok

The seat post might benefit from a shim

Iride01 

What kind of seat tube and binder clamp is it? Just a typical slot cut into the top of the seat tube with a clamp around it? Check to be certain the clamp isn't closing up completely when tightened or that the slot isn't closing up underneath the clamp. If one or both are, then you need to address that.

Locktite is a desperation move that will haunt you or another at some later date.

tough_boots

Its a Thomson Elite seatpost and it’s not a clamp— just a binder bolt. The slot is not closing up all the way.

Iride01 

So what prevents you from tightening up the clamp more? If the bolt has a shoulder on it, then maybe you are against that with the nut. In that case I'd imagine you got the wrong size post for your tube. That particular post has eighteen different diameter selections.

And even if you used the originally spec'd diameter, your your seat tube might not be that anymore.

tough_boots

Well, I imagine the binder bolt might be preventing me from tightening more. As I said, the new one is 19mm just like the original so I’ve ordered a 16mm in hopes of that allowing me to tighten it up more.

I’m pretty positive the seat post is a good fit. There’s no play at all before tightening it. Even when I use grease or liquid torque, most of it ends up on top of the tube once I re-insert the post.

thook

you should make sure it's the right size. if it's .2mm smaller, you may not notice play, but it will surely slip if you're unable to get the binder to squeeze the seat tube anymore. someone suggested a shim. you might try a cutting from a soda can. that, or tell the forum what bike what you have and the diameter size stamped on your post

btw, i don't imagine the thomson post is original to your frame. do you have the original seat post?

tough_boots

No, the Thomson is definitely not original. It’s a 26.8. I do not have the original but the only reference I can find to the bike’s original specs are for 26.8. It’s a 1987 Raleigh Technium Trilite.

When I get the smaller binder bolt, I may try the can trick as well.

MudPie

Loctite thread compound will not help.

Friction between the seat post and interfacing seat tube is what keeps the seat post from slipping. As you tighten the binder bolt, it squeezes the seat tube to the seatpost. The more squeezing force, the more friction generated.

Perhaps you can try a carbon assembly paste, which is used to increase friction with less squeezing force. I imagine it like a gritty compound that ensures carbon parts don't slip without applying so much squeezing force that it crushes the carbon members.

https://www.amazon.com/Park-Tool-SAC...92580281&psc=1

mdarnton

I had a seatpost reflector on my bike that I pulled down as a stop to keep the post from going in farther. Worked perfectly. You can even take off the reflector, if you like.

tough_boots

I tried Liquid Torque which I’m guessing is very similar.

thook

how much of the thomson post are able to insert into the frame? did you buy it new? did you cut any of the length off?

if you're using the original length for a binder bolt, i can't understand what the problem with it would be. i mean, there shouldn't be problem with it. my '82 trek came with a 27.2mm seat post...which surprised me because i thought for the age of the frame, it'd be smaller....like 26.8. as many frames of the era were.

anyway, i sold a '94 trek 520 i had to a friend and made a recommendation to him on a seat post to buy. i told him 27.2 should be the size. i even looked it up on the web. the info i could wasn't clear and i was wrong. it was 26.8, so i gave him a nice one i had to compensate for the mistake. iow's, it's quite possible your seat post is just too small. it could be 27mm for the correct size. in which case, shimming it would be a better idea than using shorter binder bolt and therefore crimping the seat lug beyond what's intended

dsbrantjr

If your binder bolt working itself loose is not the cause of your seatpost slipping, thread locker will accomplish nothing except for making it more difficult to loosen the bolt. You might try some valve grinding compound, it may be grittier than the Liquid Torque.

MudPie

You are correct. I wasn't familiar with Ritchey Liquid Torque, but after reading its description, it looks to be the same friction enhancing compound.

tough_boots

I tried the aluminum can shim. I can’t even get one layer of aluminum in there so the seatpost size must be appropriate. I’ll have to wait for the shorter binder bolt to show up and hopefully that will do it.

dabac

The slot is not meant to close up all the way.
At least, I’ve never seen one designed to do that.
The edges of the slot should remain pretty much parallel when the bolt is torqued down.

I suppose it’s possible that the binder bolt is running out of thread before it gets tight enough to hold the post.

Litespud

Loctite on the threads isn't going to help unless the binder bolt itself is loosening, but that doesn't sound like the issue, which appears to be that you're not getting sufficient clamp to start with. Could try a beer can shim if it'll fit, rough up the inside of the seat tube with sandpaper, try a different seat post (pretty much every seat post with have an actual diameter slightly different from its nominal diameter - your current one might be on the narrow end of the range). Remove the seat post and tighten up the bolt enough to ensure that there's not something preventing it from tightening all the way. A little grease on the bolt threads to ensure that it's not jamming before it reaches full "clamp". If you're not choosy, a hose clamp on the seat post will likely stop it slipping (last resort)

MudPie

Can you post a picture or two?

gkamieneski

Try another brand of carbon assembly paste. Finish Line perhaps.

freeranger

Have you tried cleaning the seattube, maybe use an alcohol soaked rag on a broom handle, or paint pole, something like that. Maybe there is some really slippery lube in the seattube. Just don't soak the rag so much that it runs down to the bb.

tough_boots

I hadn’t thought of that but I was under the impression that grease actually prevented seat post slippage.

freeranger

I always looked at grease as a preventive measure--to keep the post from fusing to the seat tube. You still want something on the post, but maybe something like carbon paste, which from what I understand, has a bit of grit to it. Sounded like you've tried other things, and that the post is sized correctly, so figured something in the seat tube is letting it slip. Let us know when you get it to stay instead of slip. I know at least one (me) who is curious.

thook

if i were you, i'd either go buy a set of digital calipers at the auto store, or take your frame and post up there and let them measure it. you really shouldn't have to go through this much trouble to get a correct seat post to stay put. unless you're running out of threads on the binder bolt like someone suggested

CliffordK

He put a couple of photos on his album page:

@tough_boots's Album:
https://www.bikeforums.net/g/user/348045
https://www.bikeforums.net/g/album/21153738



Unfortunately not a closeup of the rear... yet.

Personally I'm not a big fan of greasing seatposts. And, at least in this case, aluminum (or composite) frame, and painted/anodized seatpost, it should be fine assembling dry (if that is the case).

I like the idea of a reflector or second clamp just above the lug.

tough_boots

now looking at the close up— it’s gotta be the bolt. Strange that the original bolt was too big.