what do I need?

[nickg]

Right might replace worn bits instead of new bike. Got 8speed cassette on rear. Also will need a chain. All 12yrs old. Do I need crank aswell? Do I just search for a shimano 8 speed cassette or do I need to look for anything in particular? The rear mech is alivio and so is the front. All in mtb

 

[migrantwing]

Any Shimano MTB 8 speed groupset would be fine (I should think). The crank may be worn, so not replacing it would be false economy, but it all depends on how worn it is and without seeing it I can't say.

 

[nickg]

Are you able to recommend a complete group set to look for. Cassette chain and crank.

 

[Cubist]

Depends on your budget, but I might be tempted to steer you towards a complete upgrade to 10 speed.... Deore transmission groupset for £159?

 

[doog]

Crankset £12.65 http://www.rosebikes.co.uk/article/shimano-fc-m171-crankset/aid:443808
Chain £9.16 http://www.rosebikes.co.uk/article/sram-pc-870-chain/aid:249793
Cassette £ 7.59 http://www.rosebikes.co.uk/article/shimano-cs-hg-41-8-speed-cassette/aid:520168
shipping £7.60

Total £37