A couple of carbon questions

Neddysmith
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A couple of carbon questions

Postby Neddysmith » Mon Sep 25, 2017 10:19 am

Hey Guys,

So recently got into road cycling and bought myself a second hand road bike to test the waters and see if i liked it etc.

I have noticed when i initially start riding there seems to be a few creaks and groan from the bike, usually when putting the power down so assuming from the crank area but havent had a good indepth look because after maybe 5-10km the frame seems to settle and there is no more creaking noises and i can ride without drama.

So does carbon shrink and expand slightly with different temps, or does it settle at all which could be causing the creaking? Or should i be more looking torque or various bolts etc or possible cracking?

Cheers

madmacca
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Re: A couple of carbon questions

Postby madmacca » Mon Sep 25, 2017 11:53 am

Certainly it's worth checking the tightness of the chainring bolts.

But the most common cause of creaking in the bottom bracket area is actually the headset, as a little bit of frame flex under load will often show up there. A clean and re-grease of the headset can work wonders on the sound of your bike.

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RonK
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Re: A couple of carbon questions

Postby RonK » Mon Sep 25, 2017 12:20 pm

Depends on the bike. Pressfit bottom brackets are commonly used in carbon-framed bikes and are notoriously noisy. What bike do you have?
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Philistine
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Re: A couple of carbon questions

Postby Philistine » Mon Sep 25, 2017 1:43 pm

My first (second hand) carbon bike had a noisy bottom bracket when I bought it. I rode with it for a while, intending to fix it myself, but I couldn't do it without special tools. I eventually took it to my LBS, who replaced the bearings and warned me that the "fix" might not last long as the crankset was worn. About 3000km later the noise came back, but only at the start of a ride, rather than all the time. I ignored it at first, hoping it would go away, but, eventually the LBS had to replace the crankset and bearings. I learned the hard way that it is better to replace the bearings as soon as they need it, rather than soldiering on and stuffing up the crankset as well.

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Duck!
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Re: A couple of carbon questions

Postby Duck! » Mon Sep 25, 2017 7:00 pm

Neddysmith wrote:So does carbon shrink and expand slightly with different temps, or does it settle at all which could be causing the creaking?

No, carbon composite (to use its correct term) is the most thermally stable material used in bikes.

Start with the suggestions above. While not entirely innocent, bottom brackets get blamed for many more noises than they are actually responsible for; the worst offender is the headset. Seat post head assemblies can also be noisy, so it's worth chucking a bit of grease on the contact areas and making sure the bolts are tightened properly. Check hubs for bearing play, they can gat noisy if they're sloppy, and while you're there ensure the quick release skweres are securely tightened; if they're not tight enough they'll "walk" in the dropouts & make noise.

Modern frames with large tube sections and thin walls, regardless of material are excellent amplifiers, which will does make tracing noises difficult, because the noise resonates through the frame a long way from its source.
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Neddysmith
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Joined: Mon Jun 26, 2017 11:10 am

Re: A couple of carbon questions

Postby Neddysmith » Tue Sep 26, 2017 8:47 am

Thanks for the tips, give me a few places to start looking at, i am not overly concerned as the noises do disappear or are infrequent, just wanted to try and sort it out.

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