Matthew Myatt
Hello,
Last time I had a difficult-to-diagnose mystery bike noise, you guys were really helpful, so I
though I'd wrack your brains again. Any ideas what could be causing this?...
My friend's 12-month old bike (Specialized Sirrus) has developed a very loud cracking noise around
the bottom bracket whenever there's a fair bit of pressure on the pedals (e.g. accelerating from a
standstill).
We've had both cranks off, cleaned everything off and replaced the cranks *very* tightly, but the
noise is still there.
There are no visible frame cracks and I'm beginning to suspect the bottom bracket.
I'm pretty sure it's not the pedals as we can get it to crack by pushing down on the crank and not
the pedal.
An interesting observation that should really help to diagnose the problem is this:
Holding the bike still, with both brakes on, right crank at 3 o'clock. Stand on right pedal - crack.
That's it. There's no more cracking no matter how much you jump up and down on it until you repeat
this on the left pedal.
In other words, it's as if something (bottom bracket?) isn't seated properly. Pressing down on
the right hand side causes it to shift ("crack"). Pressing down the left hand side causes it to
shift back.
This is a really loud noise and very annoying. Any help would be most gratefully received!
Thanks,
Mat
Last time I had a difficult-to-diagnose mystery bike noise, you guys were really helpful, so I
though I'd wrack your brains again. Any ideas what could be causing this?...
My friend's 12-month old bike (Specialized Sirrus) has developed a very loud cracking noise around
the bottom bracket whenever there's a fair bit of pressure on the pedals (e.g. accelerating from a
standstill).
We've had both cranks off, cleaned everything off and replaced the cranks *very* tightly, but the
noise is still there.
There are no visible frame cracks and I'm beginning to suspect the bottom bracket.
I'm pretty sure it's not the pedals as we can get it to crack by pushing down on the crank and not
the pedal.
An interesting observation that should really help to diagnose the problem is this:
Holding the bike still, with both brakes on, right crank at 3 o'clock. Stand on right pedal - crack.
That's it. There's no more cracking no matter how much you jump up and down on it until you repeat
this on the left pedal.
In other words, it's as if something (bottom bracket?) isn't seated properly. Pressing down on
the right hand side causes it to shift ("crack"). Pressing down the left hand side causes it to
shift back.
This is a really loud noise and very annoying. Any help would be most gratefully received!
Thanks,
Mat
