Strange behaviour from rear gear cassette

[entropy1024]

Have a strange fault on my Whyte E-505. Recently when changing gears there has been no transmission of power from pedals to the rear wheel. This is intermittent, sometimes when changing gears its fine, other times not.

Found the issue is that sometimes the rear cassette gear cluster freewheels when pedalling! ie when I pedal, the chain moves the cassette round, clockwise but the wheel does not move.

Never seen this before on a bike. Does anyone know what may be wrong and how to fix?

Many thanks for any help.

 

[RustyMTB]

Sounds like your freehub is knackered. You can test by taking the chaIn off the cassette & spinning the cassette by hand. If it rotates without turning the wheel, then it's confirmed.

 

[Mik3F]

100% the freehub, my wifes bike had the same behaviour and a new freehub sorted it

 

[Bones]

Depending on the hub, you will probably find the pawls are sticking closed.
Although emtb's give them freehubs a load of stick and they soon wear out in my experience.
If it uses pawls and you know what hub it is, then you can buy buy new ones and the spring fairly cheaply.

 

[RustyIron]

Does anyone know what may be wrong and how to fix?

Yes.
You need to service your freehub. Until you get it apart, there is no telling what it needs. If you have basic tools and know what you're doing, the whole job takes half an hour. Since you don't know what you're doing, watch a YouTube video and a lot an hour. If you find that the parts are broken and worn out, it might be best to get a new hub--but you won't know until you get it apart.

 

[entropy1024]

Yes.
You need to service your freehub. Until you get it apart, there is no telling what it needs. If you have basic tools and know what you're doing, the whole job takes half an hour. Since you don't know what you're doing, watch a YouTube video and a lot an hour. If you find that the parts are broken and worn out, it might be best to get a new hub--but you won't know until you get it apart.

Bike is only a year old. Never had a freewheel fail before on any bike. Think it may be a sealed unit and will possibly need a new wheel.

 

[Mikerb]

Bike is only a year old. Never had a freewheel fail before on any bike. Think it may be a sealed unit and will possibly need a new wheel.

No.....depending on the freehub it will either be serviceable or at worst need a new freehub. It's a simple process and servicing a freehub is something that invariably needs doing a couple of times a year. Remove the rear wheel, remove the cassette....the freehub is now exposed. You can then see what type it is and use YouTube to guide you servicing it.
You could get more help here if you can say what brand wheel/hub/ cassette is fitted to your bike.

 

[RustyIron]