Freewheel cog removal
06-07-13, 05:56 PM
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Freewheel cog removal
Hi bikeforums, I'm a beginner with all this bike stuff and this is my first post so please be gentle... 
My 8 speed screw on shimano freewheel's sprockets are extremely worn, and I bought a cheap off brand replacement from ebay as a stop gap. The replacement went on fine, but within a few days the cogset would turn without turning the wheel and after removing it, noticed that the thread had stripped on the inside! A bit annoyed as it cost me £20 but you get what you pay for (unless I cross threaded but was very careful about that).
The actual rachet mechanism + screw on thread on my old freewheel is in great condition, so I want to get the cogs off the old freewheel and replace them with the cogs from the first one. Only thing is I can't find any consistent information about how to do this (and if it is even possible on my cheapo freewheel). I've read Sheldon Brown's pages but it's all a bit of a mystery. So far I've pieced together that I need to secure the largest cog in a clamp or vise, and use a chain whip counterclockwise to remove the smallest cog.
Before I go and buy a chain whip and waste a few hours in the garage, is it be possible to disassemble the freewheel in this way (picture below)? Is it likely that the cogs will be interchangeable?
Here is a picture of the freewheel: https://imgur.com/yR6Gccq
My 8 speed screw on shimano freewheel's sprockets are extremely worn, and I bought a cheap off brand replacement from ebay as a stop gap. The replacement went on fine, but within a few days the cogset would turn without turning the wheel and after removing it, noticed that the thread had stripped on the inside! A bit annoyed as it cost me £20 but you get what you pay for (unless I cross threaded but was very careful about that).
The actual rachet mechanism + screw on thread on my old freewheel is in great condition, so I want to get the cogs off the old freewheel and replace them with the cogs from the first one. Only thing is I can't find any consistent information about how to do this (and if it is even possible on my cheapo freewheel). I've read Sheldon Brown's pages but it's all a bit of a mystery. So far I've pieced together that I need to secure the largest cog in a clamp or vise, and use a chain whip counterclockwise to remove the smallest cog.
Before I go and buy a chain whip and waste a few hours in the garage, is it be possible to disassemble the freewheel in this way (picture below)? Is it likely that the cogs will be interchangeable?
Here is a picture of the freewheel: https://imgur.com/yR6Gccq
06-07-13, 06:10 PM
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8-speed screw on Shimano freewheel?
06-07-13, 06:26 PM
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Firstly, freewheel cogs aren't likely to be interchangeable between brands, so using the ones of that cheap one on your Shimano freewheel may well not work.
Secondly, that method for disassembly only works on some freewheels, others have all the sprockets held in place by a lockring like you'd find on a modern cassette system, although if anything, the freewheel in that picture probably will come apart in the way described, as I can't see a lockring.
Thirdly, 8-speed freewheels have an unfortunate tendency to bend axles - the length of axle that's unsupported between the drive-side bearing on the hub and the dropout was bad enough with 7-speed, 8-speed is even worse with a standard diameter axle, which is why most people will recommend upgrading to a cassette freehub system if possible.
Secondly, that method for disassembly only works on some freewheels, others have all the sprockets held in place by a lockring like you'd find on a modern cassette system, although if anything, the freewheel in that picture probably will come apart in the way described, as I can't see a lockring.
Thirdly, 8-speed freewheels have an unfortunate tendency to bend axles - the length of axle that's unsupported between the drive-side bearing on the hub and the dropout was bad enough with 7-speed, 8-speed is even worse with a standard diameter axle, which is why most people will recommend upgrading to a cassette freehub system if possible.
