Bike Forums - Torquing of carbon fiber bike bolts

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Torquing of carbon fiber bike bolts

Hi, all. Just bought a new carbon fiber bike (Giant Fastroad flat bar road bike) and I'm having a problem with a rattle in the saddle. I've narrowed the noise to the saddle by eliminating other possibilities. I can bounce on the saddle or slide myself fore/aft and make the noise. Nothing else does it.

Unfortunately my Giant dealer is an hour away and all I've been able to do so far is discuss the issue with him by phone. He believes that the noise comes from either the seatpost bolt not being tight enough, or the clamp that fits over the seat rails isn't tight enough.

All of that is the backstory for my real question. How real of a threat is over-torquing and damaging a carbon bike?

Giant labels all the the bolt torquing requirements right on the bike, in N-m. I don't currently have a torque wrench to tighten to spec. I can buy one -- they're not horribly expensive. However, my bike dealer is assuring me that I cannot over-torque these bolts and to have at it.

I'm currently using 3" long allen wrenches so it's pretty hard to generate a lot of torque. I fear the nightmare of over-tightening and snapping the CF, if that's even possible. Any thoughts on torquing bolts on a carbon fiber bike, and is a torque wrench necessary for routine, at-home maintenance and adjustments?

Thanks for your thoughts, ideas, and warnings!!

Quote:

Originally Posted by FloridaDave (Post 20602059)

However, my bike dealer is assuring me that I cannot over-torque these bolts and to have at it.

Did they really say that? If so, get it in writing.

Unless your dealer is certain you are only going to use that small allen wrench he is giving you very bad advice and, as AnkleWork recommended, get his advice in writing so you will have evidence when you make the inevitable warranty claim. Your 3" allen wrench is not going to over torque any of the bolts unless you are super strong but a torque wrench is a good idea anyway.

If the noise is the seatpost itself, get some carbon assembly paste and apply it to the seatpost and then tighten the clamp bolt firmly. If it's the saddle rails, you can torque them pretty tight since they are quite strong. Again, a torque wrench eliminates the guesswork.

I doubt that the saddle rails/post clamp parts are carbon. perhaps the post shaft is. I'm not familiar with the post/rails clamp design on your bike, some are more likely to loosen or need high torque or lube. One way to start hunting down noises is to systematically taking one sub assembly apart, cleaning all and reassembling with proper lube/paste and tightness. Then ride and see if there's a change.

As is often mentioned on this forum noises can seen to come from one part but actually be from a different one. So also look at your bars/stem and the cranks/pedals. Andy

Just buy the torque wrench.

^^^^^Exactly^^^^^^

Not being mean, if you know that little, buy the wrench.

I guess I don't know enough to know what you're referring to -- I've systematically narrowed the problem down, I am being careful to not damage an expensive bike, and sadly my hands are not calibrated in Newton-meters. So what do I know too little of? I'm not being sarcastic -- just would like to know how an experienced mechanic would approach this, in a way I've not. Especially when I've got a store owner telling me to torque to my heart's content...

Quote:

Originally Posted by FloridaDave (Post 20602473)

Good, then you know what to do. Take apart the source, clean and reassemble with proper lube/paste. Don't assume that the bike parts were assembled with the best methods. Don't assume that only a tightness issue is happening. Don't assume anything. By taking the sub assembly apart you establish the base line that you determine and can go back to later if problems return.

I'm not saying that your assessment is wrong. Just that many here have thought so initially and later found out otherwise. I have found clamping noises to be as often the result of surface condition as from tightness. Mere tightening doesn't give you the complete picture. Andy

Quote:

Originally Posted by Andrew R Stewart (Post 20602532)

Thanks Andy. One thing I've not considered is that the noise could be coming from somewhere off the bike, like my own rear end. But that's a discussion for an entirely different thread.

First congrats on you purchase, my wife and I have 2015 FastRoad CoMax 1s that currently have a little over 31k miles on them without any real problems. My wife's frame does have a rattle that appears once in a while. Have traced it to either the brake or rr cable running through the frame. Not much that can be done about it. She just lives with it. Anyway if your seat post is like ours the only carbon is the stem itself. The top saddle mount is all alloy. BTW we live in the Ocala area. Have you been to the Withlacoochee? It's our favorite trail in the area. Good luck with your problem and hopefully you enjoy years of pedaling your new ride.

Quote:

Originally Posted by DowneasTTer (Post 20603006)

I've heard about the Withlacoochee Trail but haven't ridden it yet. I want to do the Clean Air Ride next March, probably only the 50 mile ride, not the century. How cool -- the entire 50 miles is on the Trail.

Hole threaded in epoxy, Bolt not carbon fiber

By Using agreed upon international standards,
the numbers imprinted on the parts , tell you "how tight",
as read by using your torque wrench markings..
of what it should be.

...

Quote:

Originally Posted by FloridaDave (Post 20602473)

I'm not being sarcastic -- just would like to know how an experienced mechanic would approach this, in a way I've not.

a) With experience.
b) With a torque wrench.

I don't think that tightening the seatpost collar is the first thing to try. That's usually done if the seatpost is slipping.
With too much torque, I'd worry more about cracking the carbon frame under the seatpost clamp, not the seatpost itself. Seatposts are strong.

What sound are you hearing? A creak? or a click?
Can you stand next to the bike and lean on the front or back of the saddle or twist it to make the noise?

~~~

I've had to lube the saddle rails where they fit in the saddle's plastic sockets. It was creaking. But that was on a 3 year old bike.
Saddle rail clamps can need lube.
My rear quick release was clicking, and I was "100% sure" it was the crank and bottom bracket! Cleaning the pivot surfaces and adding a bit of grease fixed it.

Quote:

Originally Posted by Andrew R Stewart (Post 20602532)

Andy has extensive experience. Good advice.

Quote:

Originally Posted by migrantwing (Post 20603982)

a) With experience.
b) With a torque wrench.

"Good judgement comes from experience. Experience results from bad judgement."

My advice FWIW, would be to take the bike back to the shop and have them fix the issue, hour drive or not.

I don't personally use a torque wrench but I'm pretty conservative in how much I tighten things. Also no disrespect, but if you have to ask if a torque wrench is a good idea, it probably is. Better safe than sorry.

Quote:

Originally Posted by FloridaDave (Post 20602059)

If you haven’t used carbon paste on the post you might start with that. I have the Finish Line brand. A tube is less than 10$. It has the consistency of Vaseline but with some fine grit in it. I’ve heard that the use of this paste goes a long way with carbon frames/seatposts to keep things quiet and prevent over torquing bolts.
As for the torque wrench, I would say go ahead and get one. I wouldn’t recommend the Harbor Freight one since it is crude and you have to convert inch pounds to Newton Meters. One that is bike specific might be more versatile and easier to use. The Park Tools T-shaped ones with preset clicks would probably work for you.
One tip I would share is that “T” shaped wrenches can help with applying even torque that you can feel. It is like you double the force so you’re able to really snug up a fastener much more reliably than with an “L” shaped wrench that can slip off, strip out the bolt head, or fly off at a weird angle and scratch the frame.

Be sure to post an update when you get this issue sorted. Let us know what you learned and if you are able to isolate the exact cause of the noise. I’ve got a vintage titanium bike where my Ritchey carbon fiber fork either creaks or rotates to the side during rides. I think I have the solution but I have not fully implemented it yet (I’m waiting for a slightly different dimension sleeve to arrive from China - 27.2-30.1 vs 27.2-30.0. My frame is normally takes an odd size seatpost 30.0 but is now sleeved to take the more common 27.2 size post).

On that particular bike I'd recommend removing the seat post, removing the expanding wedge, and disassembling it and cleaning it, greasing the bolt and wherever the wedge parts touch, and applying carbon grip to the face of the wedge contacting the post as well as the inserted length of the post. Also lightly greasing the saddle rails and torquing that pinch bolt down isn't a bad idea and you can probably safely go pretty high in torque on the stock saddle. If you seriously over torque the seat wedge bolt you could potentially damage the post, and potentially with wildly excessive force the frame, but if you do the above and get it solidly snug it should be fine. A torque wrench isn't a bad thing to have either-- the Park ATD-1.2 is a really convenient tool for common pinch bolt torque values on carbon bikes, although a general purpose torque wrench is more versatile.

Use a torque wrench and tighten to the spec.
Also use carbon paste.

Seatpost pinch bolt, CF frame - don't over-tighten.

Saddle clamp- pretty hard to overdo it.