Gear slippage?

[Sara_H]

I was out on my folding bike yesterday, when the gears started slipping all over the place. Not sure what was going on.
Any tips on diagnosis and cure? Bare in mind, I'm a complete bike mechanics novice, I usually get a man in!

 

[Sara_H]

Sorry, should have said, its a hoptown 5 with a

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Shimano Tourney 7-speed derailleur.​

 

[BSRU]

The initial place to look is the chain to see it has stretched too much, you can buy a tool for that for a few quid.
A stretched chain will increase the wear on the rear cassette/chain rings meaning a more rapid need for replacement.
Hopefully you have not over lubricated the chain.

 

[Sara_H]

I have definitely not over lubricated the chain .

It seemed to go wrong after I turned the pedal the wrong way.

 

[accountantpete]

I have definitely not over lubricated the chain .

It seemed to go wrong after I turned the pedal the wrong way.

Do you mean that you were pedaling forwards and the rear wheel wasn't turning?

It is a reasonably common fault with the pawls in the hub sticking down and not engaging.

They fold down when you pedal backwards and then spring up and engage when you pedal forwards. However if muck gets in then the adhesion is stronger than the spring and you get that pedal turning but nothing happening symptom. Usual solution is to replace the hub or take the freehub off and spray WD40 into it in the hope of cleaning it.

 

[Graham]

Sounds quite sudden from your description - Has the rear derailleur come a bit loose at all?

 

[Sara_H]

I was stationary and moved the pedal backwards to get it into position, there was a clunking noise and after that gears wouldn't engage properly.

 

[BSRU]

Maybe the rear derailleur is not quite lined up correctly or the rear gear cable has stretched.

 

[Graham]

I agree with accountant pete, sounds a bit sudden for something to have stretched, especially as it only happened when you pedalled half a turn backwards. You'll need a couple of special tools (chain whip and cassette removal socket) to get the cassette off before you can get to the hub, so might be a bike shop job?

 

[SquareDaff]

Is the chain on the gear teeth but with the gear ring just spinning by itself and not driving the wheel?