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Jason B
12-09-2012, 04:30 AM
Finally put together my new fixie (old parts). Everything is great, but I am getting a random hollow sounding tapping noise. it sounds like something hitting the carbon frame on the inside. It only happens when riding, it doesn't happen when shaking or bouncing the frame at a stop. The sound is inconsistent but will randomly happen at higher speeds. Any help appreciated for I am about ready to rip out some floorboards to find this beating sound!

Dirt
12-09-2012, 04:58 AM
Main thing to check is drivetrain clearance up front. Seems obvious, but sometimes I overlook that. Make sure the chainring isn't too close to the frame. The occasional flex could cause it to rub or knock.

Look at water bottle cages. Make sure they're tight.

Front brake mounting bolt (if you have one) is an option They have different lengths of recessed nuts to deal with different forks.

Can you feel anything in the steering? Headset?

Loose rear wheel axle.

Those are the obvious ones and ones that you've already looked at.

Do you have a seat bag on the bike? If so, could your multi-tool be knocking on the frame through the seat bag? Make sure that the tubes are in between the multi-tool and the frame.

Sorry to be so vague with the solutions. It is hard to diagnose problems over the Interwebs.

Good luck! Love to see the new build.

Pete

dcv
12-09-2012, 06:36 AM
Sometimes I get a regular clicking under hard pedalling, synched with the pedal stroke. I haven't figured it out yet but it's bad when chain is too tight, but almost imperceivable when chain is loosened. (carbon frame).

Once I disassembled the bottom bracket (gxp) and re-greased the bearings, that made the sound go away. it's been about 1-1/2 years and think I'll try that again.

Also in the past a loose seat clamp was the culprit, had to grease the seat post too (different steel frame)

Definitely post pics, let us know if you find the source.

Vicegrip
12-09-2012, 09:13 AM
I had a rattle in my crabon framed bike that turned out to be one of the internal cables. High energy, high frequency vibration was needed to meake it sound. Added a small zip tie to each end of the cabel and pulled it tight inside the frame to fix.

Had a tight chain chainring related click on another bike. I ended up finding it when I got around to cleaning and and inspecting the big chain ring. I found a slightly bent and dinged tooth. Unbent it with an ajustable wrench and filed off the ding for the fix. Only clicked when on the big ring in front and a one of big sprockets in back. (Did someone say "sprokets"? Now we dance!)

Steve
12-09-2012, 10:53 AM
Had a tight chain chainring related click on another bike. I ended up finding it when I got around to cleaning and and inspecting the big chain ring. I found a slightly bent and dinged tooth. Unbent it with an ajustable wrench and filed off the ding for the fix. Only clicked when on the big ring in front and a one of big sprockets in back. (Did someone say "sprokets"? Now we dance!)

I'd be careful with messing with the chainring. If you look closely at one you will see that the teeth are not uniform in size or shape, and sometimes even a little out of line. It looks like the tips of some have broken off too. But that's intentional and how it looks brand new. These little differences help with the chain catching more easily.

Vicegrip
12-09-2012, 01:17 PM
^yes some systems use asymmetrical tooth groups, gearwall indentations and other methods to help instigate and complete shifting. In my case it was clear it was a rock ding and was the only tooth in the same condition. The chain would hesitate slightly then drop into the tooth gullet when rolling into the bad tooth. It did not do it when on the small sprokets and i am guessing it was due to the big cog to big ring cross chain angle. YMMV.

Jason B
12-09-2012, 03:40 PM
Thanks for the help. I am going to check the head set. Took it for a spin and really think it coming from there. I am not sure how , but it just sound like something is knocking in the headset.
Btw, here is a picture of my latest build. It was my old Postal that I cracked the hanger cranking up a hill. It killed me when my LBS said it could not be repaired. I about to hang it as a wall ornament, when I came across an ENO hub on Craigslist. I retooled it with a 46 sugino crank and a white industries 17 cog. It is amazing how light the postal is after stripping all the extra medals.
Again, thanks for all the great advice,
Jason B
2136

dcv
12-09-2012, 04:01 PM
Thanks for the help. I am going to check the head set. Took it for a spin and really think it coming from there. I am not sure how , but it just sound like something is knocking in the headset.
Btw, here is a picture of my latest build. It was my old Postal that I cracked the hanger cranking up a hill. It killed me when my LBS said it could not be repaired. I about to hang it as a wall ornament, when I came across an ENO hub on Craigslist. I retooled it with a 46 sugino crank and a white industries 17 cog. It is amazing how light the postal is after stripping all the extra medals.
Again, thanks for all the great advice,
Jason B
2136

Nice job, I love that your frame gets a second life. Personally i think the ENO hub is the key to my happiness.

Vicegrip
12-09-2012, 04:40 PM
If you get a bike that is otherwise not considered repairable let me know before trashing it. I have welded a lot of aluminum things that were deemed not repairable by others. I am not in any way a pro bike mechanic but have a good bit of experence welding up various metals.

(the car in the avatar is one of my ground up hand builds)