Hutch's Manuals - Replacing a Freewheel
Freewheels have a limited life.. and whether it be greasy mud, an over-tensioned chain or just genuine wear, sooner or later your Freewheel will need replacing.
For anyone with a BMX background this will likely seem a regular task, something that is done from time to time either at home or by a LBS. However those who have come from an MTB background, and are now running a single-speed setups, might never have had to mess about with BMX style Freewheels.
With the correct tools this is NOT a difficult job and should be simple enough for anyone with a modicum of practical ability.
Heres how its done..

(Fig.1) The oldie..
Here's the old freewheel: It was warped, worn and I wanted to replace it with a new 16t 'FAT' freewheel which cost me about £14 online.
Note: Being branded 'FAT' is a bit of a rip. They suit standard 1/8" chains instead of the weedy 3/32" chains.
(so that's about 3.2mm wide, not 2.4mm)

 

(Fig.2) Tooling Up..
To complete this job with minimum hassle and without totaling your hubs you'll need a proper freewheel tool. They cost between £5 and £15 and are a valuable addition to your toolbox
Note: Check you pickup the correct type of tool for your freewheel. Most have 4 tabs as shown in the photo.
 

(Fig.3) Fix the tool in place..
Most freewheel tools have a hole through the centre so you can attach them to your hub. This helps no end when you need to apply loads of pressure on with a spanner. It's fine to use the normal hub bolts to do this.
IMPORTANT: You must NOT bolt the tool on tight, leave it nice and loose!

  

(Fig.4) Unscrew the Freewheel..
If your have a right-hand drive setup, the Freewheel's thread is clockwise. Anti-clockwise thread is used for left-hand drive. When you pedal you are constantly tightening the freewheel onto the hub so you can expect to have to use a fair bit of force to get the thing to unscrew.
 

(Fig.5) Use of force..
If it wont budge, you COULD use a rubber/wooden mallet to *thwack* the spanner, but make sure the spanner is nice and tight on the freewheel tool, otherwise you will likely damage both.
VERY IMPORTANT: As SOON as the freewheel starts to unscrew, remove the bolt holding the tool on.

  

(Fig.6) The take-off..
Unless your threads are crossed (pray they are not), or the thing is rusted on, you should be able to unscrew the freewheel right off the thread with relative ease. You might have to use a spanner if its a bit tight, but probably not.
 

(Fig.7) The clean-up
After the old freewheel is removed, give the hub body and exposed thread a very good clean with some spray lube. It's best to use a lint-free cloth. Dads workshirt is probably perfect. It's a good idea to use a little grease on the threads ready for the new Freewheel.

  

(Fig.8) Screw on the replacement..
No real instruction needed here, you simply screw on the new freewheel, and tighten it with a spanner for the last few turns if needed. It doesn't have to be VERY tight. Pedaling around a few blocks will sort that out in no time.
 

(Fig.9) The freewheel is dead.. long live the freewheel..
So that's it, easy with a freewheel tool and a spanner right? Here's a few last minute notes about the process:
 
Note 1: In Fig.3 and in Fig.5, the reason you shouldn't tighten up the bolt much, or unscrew the freewheel while the bolt is still attached is this: IF you do, the bolt will start to pull the axle and any bearings out of the hub body with it. Without meaning to you will have fashioned a very effective bearing puller.
If you DO manage to pull the bearings out, they should be reinserted with (in order of preference) a bearing press, a bench vice or very gentle use of a hammer and blocks.
Note 2: In Fig.7, Using some grease helps you NEXT time you need to remove the freewheel.

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