Diagnostic Help
11-06-08, 10:31 AM
#1
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Diagnostic Help
I have taken up bike commuting this year and am slowly learning my mechanics but this has me stumped and I'm hoping someone can help me out.
The problem: When pedaling I recently/sometimes get a kunka, kunka, kunka sound and vibration through my pedals to my feet.
1. It's intermittent
2. It starts for know reason but will consistently quit (more than 50% of the time) if I drive over a significant bump. But sometimes goes away on it's own without a bump.
3. It's loudest in the small chain ring and the 3rd gear of the rear cog; or the mid and large chain ring and 4th gear of the rear cog (7 on the cog). It gets significantly quieter the further you are away from these combination's.
4. Bike is Davinici Milano
5. Happens only if I pedal
6. Is not consistent through the pedal stoke but not random either. Meaning it doesn't happen at 2 o'clock and 8 o'clock every time. It's more like 2, 7, 12, 5. Sequential but by an odd number increment that I haven't figured out.
I suspect the crank bearings but it doesn't make sense to me that it would be louder in certain gearing then others.
Thank you in advance for your thoughts.
The problem: When pedaling I recently/sometimes get a kunka, kunka, kunka sound and vibration through my pedals to my feet.
1. It's intermittent
2. It starts for know reason but will consistently quit (more than 50% of the time) if I drive over a significant bump. But sometimes goes away on it's own without a bump.
3. It's loudest in the small chain ring and the 3rd gear of the rear cog; or the mid and large chain ring and 4th gear of the rear cog (7 on the cog). It gets significantly quieter the further you are away from these combination's.
4. Bike is Davinici Milano
5. Happens only if I pedal
6. Is not consistent through the pedal stoke but not random either. Meaning it doesn't happen at 2 o'clock and 8 o'clock every time. It's more like 2, 7, 12, 5. Sequential but by an odd number increment that I haven't figured out.
I suspect the crank bearings but it doesn't make sense to me that it would be louder in certain gearing then others.
Thank you in advance for your thoughts.
11-06-08, 01:17 PM
#2
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Bottom bracket bearings would probably make the same noise at the same spot on every crank-revolution. I'd try a new chain first.
11-06-08, 02:13 PM
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You trying standing to the side of your bike and tugging (not too hard) back and forth on the crankarm. If there is play or clunking then it is probably the BB.
Could be chain or RD but I would start at the BB.
Could be chain or RD but I would start at the BB.
11-06-08, 02:20 PM
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I'd check the pedals too. Pull on the body of the pedal and see if there is play in the bearings.
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Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
11-06-08, 05:39 PM
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Thanks guys for the thoughts. Appears I've found the answer, on this mornings commute the rear cog fell off. I guess that would do it :-)
