Clunking bb or cranks?

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DickP

Regular
Good morning,

Since my last posting on here I have purchased a Cannondale CAAD8, and done >300 miles on it so far. It'll be going in for its first free basic service soon, but in the interim before it goes in I am using it regularly and found that the bike has developed a clunk from the bb/crankset area. This happens only when putting the power down and most commonly happens at positions 1 to 2 o'clock on the downstroke. It's an identical both sides of the crankset (left and right pedals), and can be felt through the pedal when it does clunk.

I cannot replicate the fault by hand, cannot feel any play anywhere and all the components spin smoothly.

Is anyone able to provide advice as what the likely culprit is? Is it possible that the crank arms have loosened in the sub 300 miles of use since assembly by the bike shop? Or does this particular model of bike have a history of weak bb?

As a side note, I have already had to index the rear derailleur in the time I have been using it. Is this considered normal within the mileage I have covered on a new bike or was it likely not set correctly to begin with?
 

Tim Hall

Guest
Location
Crawley
Good morning,


As a side note, I have already had to index the rear derailleur in the time I have been using it. Is this considered normal within the mileage I have covered on a new bike or was it likely not set correctly to begin with?
Can't help with your BB question, but re-indexing is normal, as the new shiny cables will have bedded in/stretched a wee bit.
 
OP
OP
D

DickP

Regular
Hi again,

Just to bring closure to this - the symptoms got worse on the ride home from work this evening so dropped into the bikes shop I purchased the bike from. They found that the bb was loose. It's now fine again.

Cheers!
 

ColinJ

Puzzle game procrastinator!
I was just about to tell you about my CAAD5 which had the same problem. I thought the BB had probably worn out, though I could not hear/feel anything wrong when twisting the cranks by hand. I was removing everything anyway to change the bike over to a triple chainset and discovered that the BB cup had come loose so I could remove it using just the BB tool without needing a spanner on it!
 
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