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Issue with BB

Old 01-12-19, 07:43 PM
  #1  
salad_goat
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Issue with BB

Hello,
As per the title it seems as though sometimes when I put pressure on the pedals it get a grinding noise and there is no resistance. The bike will not go forward. It seems to not catch and my pedal stroke just "goes through". The freewheel seems fine and I don't believe it to be the issue. I have my single speed set up 40x17. I am thinking I may need a new BB. Thank you
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Old 01-12-19, 07:46 PM
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fietsbob 
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Ok i guess freewheel pawls not engaging (cold stiff grease), but you say not..You are there , took wheel off and checked.. ?








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Last edited by fietsbob; 01-12-19 at 10:11 PM.
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Old 01-12-19, 08:00 PM
  #3  
Andrew R Stewart 
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For you to not have any "power" propelling your rear wheel forward when otherwise pedaling means that the connection between the pedals and rear tire is broken. (Assuming you are describing the problem correctly). The BB has nothing to do with this connection, it only locates the crank arms and reduces the friction when rotating them.

So back to basics. How are you determining that you are experiencing "there is no resistance. The bike will not go forward"? Can you push on the pedals with the bike already stopped and have them rotate but there's no attempt for the bike to want to move forward? If so then is the chain moving with the cranks/pedals or it is also stationary? If the chain is moving with the pedals is the rear cog also moving but the wheel isn't? Or are you only thinking there's "no resistance" when you're riding the bike?

For the pedals/crank arms to be rotating but not the chain the connection between the chainring and the arm has to be slipping (and if the construction is a two piece that has been pressed together this fit could be loose). For the chain to also be moving with the pedals but the cog isn't means that the cog/chain engagement is somehow bad. For the cog to also rotate but not the rear wheel means that the cog/rear wheel connection is bad.

All this could be happening and the BB could also have it's own issues (the grinding is a common noise from a worn out BB). But the BB has nothing to do with the pedals pulling the chain which then pulls the cog which then pulls the rear wheel forward.

Give this some thought, reask if you can't make sense with what I say. report back if you find something or can better describe the problem. Andy
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Old 01-12-19, 10:42 PM
  #4  
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You say the freewheel "seems fine." Do you mean that the rear wheel rotates freely when manually spun?

If you drop the chain off the crank and try to rotate the cranks, is the rotation smooth? If not, the bottom bracket could be the problem. What type of bottom bracket do you have? A cartridge bottom bracket is generally unserviceable; you replace it with a new cartridge. A cup-and-cone bottom bracket can be serviced by opening it up and inspecting for worn or damaged parts and replacing as indicated.
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Old 01-13-19, 12:41 AM
  #5  
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Do you have an Ashtabula crank?
That's the only scenario that would make sense to me per your description.

As asked- DOES the chain move with the pedals or NOT?
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