Knocking noise when freewheeling

[andylaw79]

I've recently converted an old MTB to single speed for the commute but there is a loud knocking noise when freewheeling. Its a bike that hadn't been used for years and you could hear this knocking noise before I converted it. Thought it was caused by a worn out BB

I've put on a new crank set and BB and this noise is still very apparent when freewheeling, not when pedaling. I've checked the BB and cranks again to see if I've fitted them correctly and they are, but I'm at a loss as to what is causing the knocking sound and I'm hoping it's not a frame defect.

Any suggestions?

 

[BIGSESAL]

I am having a similar problem with my road bike. Apparently, it could be the bearings in the hub. It would make sense if the bike has not been used for a while.

 

[andylaw79]

I am having a similar problem with my road bike. Apparently, it could be the bearings in the hub. It would make sense if the bike has not been used for a while.

Thanks for the suggestion. Wouldn't I hear the noise when pedaling as well though? I can only hear it when freewheeling.

Will check this weekend anyway, gives me an excuse to tinker.

 

[02GF74]

single speed - so is that a fixed rear hub?

how do you freewheel - take your feet off the pedals? as surely they would spin if you are moving with a fixed hub?

 

[jimboalee]

Are you using the multiblock screw-on freewheel?

If one of the small ball bearings has colapsed in the freewheel body, it will sound like a 'knocking' because the sound goes up the stays and around the frame, amplifying as it goes.

 

[andylaw79]

single speed - so is that a fixed rear hub?

how do you freewheel - take your feet off the pedals? as surely they would spin if you are moving with a fixed hub?

No not fixed, just replaced the old cassette with a single cog and spacers, makes freewheeling easy

 

[tyred]

I would say freewheel related. The fact it only makes a noise when coasting is the clue. The freewheel bearing isn't turning when you're pedalling. If the bike wasn't used for a long time as you say, you could try working some oil into the freewheel. It may be gunged up as the grease has dried out. I had this on a bike (5 speed block) that I hadn't used in years and oiling helped but didn't eliminate it completely.

 

[andylaw79]

I would say freewheel related. The fact it only makes a noise when coasting is the clue. The freewheel bearing isn't turning when you're pedalling. If the bike wasn't used for a long time as you say, you could try working some oil into the freewheel. It may be gunged up as the grease has dried out. I had this on a bike (5 speed block) that I hadn't used in years and oiling helped but didn't eliminate it completely.

Thanks, will be tinkering at the weekend then. Hopefully bearings won't be too knackered.