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Frame/seat tube issues.

JohnE

filthy rascist
May 13, 2005
12,644
661
Front Range, dude...
So my trusty 98 Jamis Dragon has developed issues with the seat tube. My seat will no longer stay up, thats right, I have problems keeping it up. There are no obvious cracks in the tube or around the seat bolt binder area. Can the collar area have stretched out? Bolt is in one peice, nothing else seems amiss to my non framebuilding eye, although there is a strange line around the collar area, inside the seat tube, about a quarter inch down. Any ideas? If it matters, it has a Thomson post in it, and a bolt, not a QR.
Anybody? Bueller? Bueller?
 

jdcamb

Tool Time!
Feb 17, 2002
15,936
3,161
Nowhere Man!
Have it reamed out to the next size up. Then replace your seatost with that size. Or shim it out with a beer can.
 

reflux

Turbo Monkey
Mar 18, 2002
4,622
2
G14 Classified
Funny, as I've been having similar issues with 2000 Dean hardtail, also with a Thomson seatpost. Part of me is thinking the seatpost has worn down (thinned) in that small section, thus preventing the clamp from applying adequate pressure. How old is your Thomson post? Mine is going on 6 years. Hmm, that doesn't sound good once I put that to words.
 

HAB

Chelsea from Seattle
Apr 28, 2007
10,581
883
Seattle
Get some special carbon seatpost compound from your LBS. It's basically grease with tiny glass particles in it. It can help stop slipping seatposts.
 

Cru Jones

Turbo Monkey
Sep 2, 2006
3,032
0
Hell Track
Which is why the "cool kids" are incapable of pedaling their bikes anywhere, so they resort to cruising sidewalks and hucking curbs on their Big Hits. :disgust1:
While I agree that is the wrong tool for the job, I'm not so sure they're incapable. Pedaling is a little old fashioned. We like to build and ride stuff that requires little to no pedaling. :biggrin:

 

CrabJoe StretchPants

Reincarnated Crab Walking Head Spinning Bruce Dick
Nov 30, 2003
11,569
422
Groton, MA
Ummm... before you try reaming or glass filled grease (ye gods and small fishes...) get out your vernier calipers and measure O.D. of seatpost and I.D. of tube. Are you sure you started out with a correctly sized seatpost?
Something tells me if it were the wrong size he would have noticed in the past 10 years...
 

DirtyMike

Turbo Fluffer
Aug 8, 2005
14,240
831
My own world inside my head
I am thnking a couple different things from a couple different people.

1st, Calipers like JBP says, Maybe not to check if you have the wrong size to begin with, but to see if its worn

2nd Might be time for a new seatpost and clamp. Get something ridged like the thompson, or others like it.

3rd If that doesnt work, the carbon grease works wonders. Great stuff, slick as hell till you put some rpessure on it.

4rth, and this is mine, Aluminum dust can be extremly slick, try taking the seatpost out, cleaning it with a decent "hot" solvent and a brush<dishsoap and hotwater works great> and also cleaning the inside of the seat tube in teh same manner, nice long bottle brush should do the trick.

5th I would only resort to reaming a tube out to the next size as a last resort, for the obvious reason, your taking metal out of it to do so, effectivly weaking the tube. How much are you weaking it? Cant tell you that part, but its a part on my own bike I dont want to fail.
 
I dunno - you can crank down pretty hard on a bolt. If you presume no movement normally, I have a hard time coming up with a rationale for a seat post starting to slip.

Most of the horror stories you hear or read about have to do with tubes stuck in by corrosion, not with them getting loose.
 

HAB

Chelsea from Seattle
Apr 28, 2007
10,581
883
Seattle
While I agree that is the wrong tool for the job, I'm not so sure they're incapable. Pedaling is a little old fashioned. We like to build and ride stuff that requires little to no pedaling. :biggrin:

I kid. Pedaling is fun, so is riding stuff that dosn't require much. Hell, pretty much anything that has to do with riding a bike is fun.
 

-dustin

boring
Jun 10, 2002
7,165
1
austin
my bet is that the seatpost is crimped. is it dropping and dropping and dropping, or does it seem to only drop to a certain point?

Is the bolt in the binder greased?
 

JohnE

filthy rascist
May 13, 2005
12,644
661
Front Range, dude...
The post already is a Thomson, and it is new as of about 18 months ago...

Yes, it is the right size...this aint my first rodeo.

It is slipping, seemingly to about the same level every time, now that I thhink about it. There is no evident crimping on or in the seat tube.

The binder is greased, but what if any effect would that have on slippage? You lost me there...

I am thinking beer can shim, but first I need to find someone who drinks beer from a can! That failing, the carbon grease.
 

brungeman

I give a shirt
Jan 17, 2006
5,173
0
da Burgh
The post already is a Thomson, and it is new as of about 18 months ago...

Yes, it is the right size...this aint my first rodeo.

It is slipping, seemingly to about the same level every time, now that I thhink about it. There is no evident crimping on or in the seat tube.

The binder is greased, but what if any effect would that have on slippage? You lost me there...

I am thinking beer can shim, but first I need to find someone who drinks beer from a can! That failing, the carbon grease.
you need to try some Dale's Pale ale... prolly the best beer you will ever drink from a can! You will thank me when you do try it :thumb:
 

-dustin

boring
Jun 10, 2002
7,165
1
austin
The post already is a Thomson, and it is new as of about 18 months ago...

Yes, it is the right size...this aint my first rodeo.

It is slipping, seemingly to about the same level every time, now that I thhink about it. There is no evident crimping on or in the seat tube.

The binder is greased, but what if any effect would that have on slippage? You lost me there...

I am thinking beer can shim, but first I need to find someone who drinks beer from a can! That failing, the carbon grease.
Crimping would be on the post, not seattube.

Bolt being greased reduces friction allowing proper torque to be achieved.
 

Wumpus

makes avatars better
Dec 25, 2003
8,164
154
Six Shooter Junction
The Thomson in my Jamis(2004) slipped when it was new. Loco gave me Stinkyboy's Salsa Liplock binder:busted:, and I haven't had any problems since.
 

JohnE

filthy rascist
May 13, 2005
12,644
661
Front Range, dude...
No, also no crimping on the post...its only been in one bike, so it stnds to reason that it and the tube would be crimped.

I think I will call the Mythbuster geeks. And then get the carbon grease.
 

DirtyMike

Turbo Fluffer
Aug 8, 2005
14,240
831
My own world inside my head
Try this, take your seat post out, reach in the tube with your finger as far as you can, and see if you can wipe anything out of the tube, like aluminum dust, I am just curious, I have seen this alot and seen seat posts slip because of it.
 

CrabJoe StretchPants

Reincarnated Crab Walking Head Spinning Bruce Dick
Nov 30, 2003
11,569
422
Groton, MA
you need to try some Dale's Pale ale... prolly the best beer you will ever drink from a can! You will thank me when you do try it :thumb:

TRUE THAT!


I couldn't think of the came of the company when I went into the store looking for some (figured keep my eyes open for the only IPA in a can).

Me - *looks around*
Employee - "Can I help you find something?"
Me - "Yea, I forget who makes it, but it's an IPA that comes in a can."
Employee - "Erm....we have bottles of IPAs."
Me - "O RLY?"
 

JohnE

filthy rascist
May 13, 2005
12,644
661
Front Range, dude...
Try this, take your seat post out, reach in the tube with your finger as far as you can, and see if you can wipe anything out of the tube, like aluminum dust, I am just curious, I have seen this alot and seen seat posts slip because of it.
Stuck finger in, rubbed it around. Came out slightly dirty and greasy, no dust.