Rear Cassette Issue

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Hi folks, hoping to pick a more informed brain again if possible.
Currently commuting on a hardtail MTB 15 speed hack, and have noticed third gear on the rear cassette is disintegrating! So, have found a cheapie (£10) 5 speed replacement, but was wondering whether ( and how) I could put a 7 or 8 speed cassette on, with a replacement gear change shifter, and shift mechanism and of course chain? (Front mech appears fine) Or is this too simple an idea? Thanks in advance for your thoughts

 

[e-rider]

I'm guessing that you currently have a screw-on freewheel rather than a cassette.

So you can't fit any cassettes - only freewheels.

6 speed might be fine depending on your rear hub, 7 maybe too but probably not without some adjusting of the rear hub (dishing and axle spacing) You'll not need new shifters but if you want to use the extra gear then you obviously will need new shifters.

I would replace with similar 5 speed and continue riding - don't waste your money and time on this as it'll turn into a headache and you'll still have a crappy hack bike at the end!

 

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Thanks for the info I'm inclined to agree; had a look and am now confused between a shimano cadet, or a Shimano Tourney/TY Cadet Multiple Freewheel, or are they interchangeable?

 

[e-rider]

All Shimano freewheels fit in the same way - they screw on. Getting old ones off is not always easy if they've been on there for years.

What you need to look for is:

1.The freewheel has the same number of cogs as the old one ( eg.5 )

2. The gear ratios are pretty much the same as the freewheel you are replacing. ie. the smallest cog is about the same size (12, 13, or 14) and the largest cog is about the same (usually 28, 30, or 32)

Just get one almost the same as the one you have and you'll have no problems.

 

[e-rider]

...and, if you replace the freewheel, buy a new chain too. 3/32" width for 5 speed systems.

 

[andrew_s]

All Shimano freewheels fit in the same way - they screw on. Getting old ones off is not always easy if they've been on there for years.

To get a Shimano freewheel off, you need the correct Shimano freewheel remover - either the Shimano one, or the Park Uniglide one. If it's not Shimano, then there are a variety of other tools on the Park link.
Take care when buying, and watch that you don't get sold a cassette (lockring) removal tool like this. The freewheel tool has splines 0.5mm high but the cassette tool has splines 1mm high and thus doesn't fit.

It's best to fit the remover, using a loose QR to hold it in place, then clamp it in a solid bench vice and turn the wheel to crack it loose. A spanner will probably require an extension tube to get enough leverage.

Alternatively, let a bike shop do it for you.

 

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Very detailed advice guys, thanks a lot for your time! Will let you know when I wreck everything!