[johngfoster]

How tight is too tight to tighten a seatpost on a carbon frame? Mine is creaking but I can see small cracks at the bottom of the slot in the carbon frame.

 

[Friction_Shifter]

are you sure you know where the creaking sound is coming from? could it be coming from the small cracks in the notch of the frame? depending on the design of your frame in that area its possible that tightening further could put tensile force down in the notch which could make it worse. I'm thinking the creaking is coming from there. A couple drops of oil would probably get rid of it, but I'm not recommending to do that. If that crack is the problem you want clean surfaces to fix it.

 

[johngfoster]

Thanks for the reply. How would one go about fixing it if that were the problem?

 

[Cory]

2nd the motion on positively locating the creak

I'm with Friction Shifter--be sure you know where the creak's coming from before you apply any more torque. Bike noises are notoriously hard to find, and they can "telegraph" through the frame so they seem to be coming from somewhere else (at least that's true with steel; I don't know about carbon). Could be something as simple as a loose seat clamp, and I once chased an intermittent tick-tick-tick that turned out to be the tip of my shoelace hitting the crankarm. You might try spraying or dripping a little lube around, one potential spot at a time, to see if you can quiet it. Once you locate it, you can figure out a permanent fix.

are you sure you know where the creaking sound is coming from? could it be coming from the small cracks in the notch of the frame? depending on the design of your frame in that area its possible that tightening further could put tensile force down in the notch which could make it worse. I'm thinking the creaking is coming from there. A couple drops of oil would probably get rid of it, but I'm not recommending to do that. If that crack is the problem you want clean surfaces to fix it.

 

[Friction_Shifter]

Is the frame still under warranty? This may or may not be covered. I think it should be but they might disagree(if I was the original purchaser, and knew that I never cranked down on the binder bolt (which I never do), etc,etc I would get it covered). As far as fixing, I can't comment. I think this kind of fix is better left to the manufacturer. Patching a surfboard with fiberglass and epoxy is difn't than fixing a very small load bearing spot on a bike. More than likely if you would try to fix it youself it would be cosmetic only. If you end up wanting to go the DIY route (which I don't recommend)start by drilling a small hole at the crack tip(and it may be difficult to see the very end of the crack). Ride at your own risk.

 

[johngfoster]

Well, the deal is this: it only creaks when I rock forward and backward in the saddle. I think I may have cranked down too hard on the bolt, that's why I posted my original post: how tight is too tight? And no, I'm not about to go drilling holes in my CF frame bike just yet. That would really void the warranty!

 

[Friction_Shifter]

what brand and model of frame?

call the manufacturer and talk to one of their tech support people to get recommended torque.

in no way was I trying to imply you cranked down too hard(and I don't think you thought I was either). That slot is a stress concentrator region to begin with due to the fact its a slot(typically there is a hole at the bottom of the slot to lessen the stresses). If there were any rough areas or small chips (smaller than you could even see maybe) there to begin with it will further amplify any stresses(and could lead to cracking). It is reasonably/quite possible it wasn't your fault at all but rather a manufacturing defect. That area is a vulnerable area for CF frames(much less in metal frames bc metals are much less brittle than epoxy).

 

[BikeGeek]

50 inch pounds is about right on most carbon frames. The crack at the bottom of the slot should definitely be a warranty issue unless you cranked down the clamp with out a post in the frame which would flex the frame beyond what was intended. Calfee does carbon repair on all makes if they don't warranty the frame. I don't have any idea on cost though.

 

[Tlaloc]

50 inch pounds on your Trek. Don't lubricate it, Seats are known for creaking.

 

[johngfoster]

Thanks for all the replies. I went back and inspected the saddle and seat post more closely. I actually think the creaking may be coming from the saddle and not the seat post. The cracks in the frame are only about 2-3 mm off the bottom of the slot, so how serious this is I don't know, but I don't want to send it in and be out a bike now when I need to be training for an up-coming century.

 

[the bull]

Thats a big crack I would send it back.
If it you wait for it to break you might have problems when you go to warranty it.

BTW lube the saddle rails with a little grease.

 

[ciao bambino]

I had a similiar problem.
I went over the bike from top to bottom until I found it was at the seatpost bracket/collar.
When my collar was tightened, the two sides were pulled together and the creak came from that point of contact. I loosened the collar, and put a very small piuece of tape/foam in between the two ends of the collar and problem solved.