What is causing noise/vibration high power input on right hand (drive side) crank?

Question

I am getting a repetitive grinding sound/slight vibration while fully mashing on my Kona-humu single speed.

Description of Problem This grinding is more similar to what you would hear from an un-greased chain (maybe clicking is a better term) but much loader. This noise/vibration is also accompanied by a slight resistance. It only occurs during hard pedaling and only during right hand crank input.

Attempted diagnosis Since the issue only occurs during hard pedaling I've had a difficult time coming up with reasonable ways to diagnose. After the first 5-10 cycles I am spinning fast enough I cannot provide the needed input to reproduce the noise/vibration. I have tried to use brakes and building to hold me up right and put lots of pressure on the drive train to flex the frame and see where there may be rubbing. This has not produced much.

Possible Issues

• Chain line - I'm thinking it could be a chain line issue when the frame is torqued. Eyeballing is the chain line looks good to me without a load on the drive train, and it was recently inspected while installing a new BB at the LBS.

  1. Front chain ring - If the chain line is off the issue maybe from the added friction of the chain "popping" as it engages and disengages the chain ring.
  2. Rear cog - Same issue as the Front chain ring but happening on the rear cog
  3. Front chain ring guard - While recently installing a new BB the LBS noted the extremely tight clearance on the chain ring guard. Doing my best to diagnose as I ride I couldn't see an obvious collision with the chain ring guard, but it's hard to tell for sure while moving.
  4. Frame - I'm fairly certain there is just too much clearance in all directions for this to be an issue.
  5. Something else - Maybe there is an additional issue I'm not aware of?

• Rear tire rubbing on frame - The wheel is fairly centered in the frame with about a half inch on either side and again I don't see this happening while riding.

• Something else altogether?

Answer 1

Did this sound start when you took the biek to the LBS? What else did the LBS touch?

See if you can take the chain guard off temporarily to see if the sound goes away.

Your description also sounds a lot like a BB that the shop overtightened or under tightened. If you have a torque wrench you could investigate this yourself, otherwise I would take it back to the mechanic that installed that BB and ask for a double check.

Answer 2

I've occasionally had this when the drive side axle was slipping in the drop out. When enough torque was applied to the pedals the axle moved just enough that the front of the tyre was rubbing on the inside of the left chain stay.

You could check the paint there and see if there is any evidence of rubbing. If this is the problem, a chain tug would solve it.

Also, how close are your brakes to the rims? Maybe a bit of flex is enough to cause the brake to rub.