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Tuesday, 27 July 2010

Changing a freewheel

The Yuba’s freewheel has been making a knocking sound for a while now.  It has been intermittent, which is why I have put up with it for so long.  I have had the replacement freewheel and chain for a while but the knocking stops often enough for me to put it off.  Whilst I have changed a few freewheels in my time, I thought I would write about it to help others who have not.

It may seem odd that a bike which costs as much as the Yuba would come with a freewheel instead of a freehub and cassette.  Yuba state that it is their intention to make the Yuba as easily serviceable as possible, wherever in the world the bike may be.  Freewheels are available almost everywhere, cassettes may not be.  Freewheels are more wasteful because you throw away the internal ratchet mechanism with the cogs, whereas with a cassette the ratchet mechanism is built onto the hub.  This does make replacing a faulty ratchet mechanism easier, although it is usually the cog teeth which wear out when a freewheel or cassette need replacing.  The freewheel is also the reason why the Yuba comes with a 14 mm rear axle rather than 10 mm, the ball bearings which connect the axle to the rest of the wheel are further away from the part of the axle on which the frame sits on a freewheel system, making it easier for the axle to become bent


This is why Yuba rear wheels come with 14 mm axles, and this is why replacing the rear wheel with a cassette hub with a 10 mm axle doesn’t reduce the load capacity of the bike, as long as the wheel is still 48 spoke.

To remove a freewheel you will need a freewheel removal tool (slightly different shape to a cassette/centrelock tool), an adjustable spanner (wrench) and usually a lot of shouting and swearing. 



To unscrew the freewheel you need to turn the removal tool anticlockwise.  This is often difficult because the freewheel is screwed on tight by the process of riding the bike.  This can be demonstrated by the fate of the first adjustable spanner I used:



After a quick trip to Clas Ohlson  and I returned with an even longer adjustable spanner, made from stronger metal


Once removed, you can see the treads on which the freewheel sits:


It is worth making sure theses are greased before putting on the new freewheel, because you’ll have to take it off one day.  I would have serviced the bearings whilst I was at it if I had the 19 mm cone wrenches the Yuba rear wheel needs.

Screwing on the new freewheel is a simple as it sounds.  You will need a new chain too though.  When chains are used, the holes in which the pins sit stretch slightly, increasing the lengths of the links.  This wears the teeth on the freewheel or cassette so you don’t notice.  If you use an old chain with a new freewheel or cassette you will wear the teeth much faster, plus the bike will feel like the chain is full of gravel until the teeth wear to fit the old chain.  Luckily chains are cheap, unless you are planning to buy something ridiculous like this.  The Yuba needs about 1 and a half chains to make up the required length.

I also decided to change the tyres and add a permanent rear light (from Clas Ohlson) whilst I was working on the Yuba, it seemed to make sense to keep the Kona’s brown Fat Franks and sell it on with the older black ones.



Now all I need is a B67 saddle in honey to match the tyres.

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