[Dave In Florida]

I have a Redline Monocog 29er with a fixed seat post clamp that keeps sliding down during a ride. I was thinking of maybe crimping the seat tube of the frame a bit (its got a notch cut out of the front to allow it to compress) but don't really want to screw anything up.

How have you corrected this?

 

[majura]

1) Make sure there is a lot of grease inside the seat tube, if not whack some in.
2) Take out your seat post on the trail, get a handful of dirt and lightly coat it.

Sometimes with manufacturing either the seat tube or seat post can be slightly off. In this case sometimes a shim or larger seatpost diameter may work. But I'd take it to the LBS before committing to a new purchase.

 

[Ericmopar]

You may have a undersized seat post.
Notice how close the sizing is.
26.8 mm
27 mm
27.2 mm
30.9 mm
31.6 mm
You may have a 27 mm post in a 27.2 mm seat tube for example.
You may also have a seat post clamp that is the wrong size for the outside diameter of the seat tube.

Later, Eric.

 

[DIRTJUNKIE]

You may have a undersized seat post.
Notice how close the sizing is.
26.8 mm
27 mm
27.2 mm
30.9 mm
31.6 mm
You may have a 27 mm post in a 27.2 mm seat tube for example.
You may also have a seat post clamp that is the wrong size for the outside diameter of the seat tube.

Later, Eric.

I agree with Eric this is a common mistake.

 

[Dave In Florida]

I'm not doubting you guys, but shouldn't it have the correct parts on it since it was a built-up bike and not a frame that the shop put together?

 

[DIRTJUNKIE]

I'm not doubting you guys, but shouldn't it have the correct parts on it since it was a built-up bike and not a frame that the shop put together?

Well hopefully, but people do make mistakes. The builder may have grabbed the wrong size and installed it. Seeing how the tolerances are so close, it some times is not noticeable until it is ridden for awhile. Take the bike back and have them check it. Better yet take it to another bike shop first and have them check it. I would highly suggest not riding it like this any longer before figuring out the solution. You are at high risk of cracking your frame in that area if you continue riding it like that.

 

[KONA_in_SB]

2) Take out your seat post on the trail, get a handful of dirt and lightly coat it.

I would advise against this. If your like me and are constantly rasing and lower your your seat during rides the dirt + grease will act like sandpaer and over time bore out the seattube on your frame. That wouldn't be too good. This might not be an issue if you keep your seat at the same hieght all the time but I still wouldn't do it myself.

Also, aluminium from your favorite beer can makes a good, cheap shim.

 

[oohsh_t]

I had the same problem,
Turned out to be my seat post collar slot didn't line up with the tube slot...
I had it bass ackwards.

Works much better now.

 

[Finch Platte]

There's a thread about this on the NorCal board.

fp

 

[ettore]

I had this problem on my Superlight (30.9 or whatever I believe, not that it really matters). I found that adding or removing grease really made no difference. What "DID" make a difference, however, was greasing the little screw that tightens the clamp.

I found that the bolt was binding, giving me a false indication of tightness. Basically, I was putting 65in·lb of force without grease and the seatpost was sliding. When I greased the bolt, it now only requires just over 40in·lb and the seat hasn't budged in a few months (since I figured out this "trick").

 

[Manmountain Dense]

Forget grease. Get the good stuff. Works like a charm.

 

[SSteve F]

I would also recommend against dirt. Clean the seat post/tube and coat the seatpost with...chalk. Old tip from MBA that worked for me.

 

[ArmySlowRdr]

seat pots can be maddening. On my roadie I've found if I have it tight enough to not slide it creaks--grease or no.

 

[Bartman]

I finally solved the creeping seet post once and for all. Purchase a seat tube clamp that is the same size as the post, or as close as possible. Dremel off the ridge that is machined onto the clamp. Place it on the post above the original clamp and it acts as a stop and you won't be forced to overtighten the clamp. I also slide an O ring in between to stop the metal to metal contact. Hope that helps.

 

[Verewolf]

What Manmountain Dense said above.

I use Tacx Dynamic Carbon Assembly Paste on all my carbon and aluminum seatposts and bars.
Will not slip plus you use 30% less torque.

 

[texas]

what worked for me.

Mine used to slip. My problem was I didn't have it tight enough. Make sure everything is clean and well greased, including the cam on your clamp. Then get the thing as tight as you can. i.e. if you can close the thing without pushing fairly hard on it you may want to make it tighter.

 

[Atomic300]

I have this same problem on my hybird but not on my mtn bike. My hybird has the allen wrench type (don't know how else to explain it) closure. Is it possible to put the old fashion close do hickey on it?