I need to replace my cassette (Shimano HG30 8speed 11-32) and chain (KMC Z7) that is currently on my bike (pinnacle Aura), however these parts are now discontiuned and I need to find the replacments. I have been recommended the HG51 cassette but don't know which chain to get. Can anyone help?

Any 8s chain will be fine. You can stay with a Shimano chain, or possibly save money with a comparable quality KMC chain. (KMC makes many of Shimano's chains)

IMO the best value in chains is in the middle of the product range. Each makers best chain is better than it's second best chain, and so on down the line, but near the top the cost differences are much greater than the functional differences, so I buy the 2nd of 4 models, or the 3rd of 5 or more.

+1 for the chain advice.

8 speed cassettes are still out there, the LBS should be able to get you one. Here's a SRAM 11-32 8 speed cassette for $17 shipped: https://www.ebay.com/itm/Sram-PG-830-...item20c3615c0d

Suggest that you get a chain which has a master link which does not require a chain tool to remove and replace. SRAM, KMC and Wipperman make them. You will still need a tool to cut it to length initially. 8 speed cassettes are still easily obtainable.

Also, if you want to change your gearing, now's the time to get a different set of cogs on your cassette.

Many people have no need for a 32 tooth. YMMV

Even more have no need for an 11 tooth.

I've upgraded to an 8cog setup on my 92 Paramount.
LBS suggested one of the SRAM 870 chains.
Had in two seasons and 5K worth of miles and it's worked beautifully.
(Caveat being I don't hammer. I tend to spin )
Nice part is the smart link that allows easy disassembly and assembly of the chain

As I've recently discovered, 8spd cassettes come in two varieties. The one where each cog can slide seperately onto the freehub and the one where the last 3-4 cogs are permenantly mated to a spider which slides onto the freehub.
If you're ordering one from eBays venders you need to ask that question.
I'm unsure what the deal is with the 8spd cassettes and Harris Cyclerys statement of them no longer being 'customizeable' .
The width of cogs for the 7spd cassettes and the 8 spd are pretty much the same. Use the 8spd spacers (Loose Screws sells em)
I just put togeather a nice 13 15 17 19 21 23 25 28 setup that has even spacing thruout. Bought the 12-25 on eBay and used a 28t 7spd cog to round it out. (substituted the 28 for the 12)
I dislike the large jump so many mnfg. 7/8spd cassettes offer in the teeth between a 6th cog and the 8th.
Universal Cycles offers a selection of 8spd cassettes, Harris and Loose Screws do as well.
If you find you'd like to grind the heads off the 3 rivets holding the cassettes together and play with cog changes many of your LBS have a ton of 'old stuff' in shop back rooms and basements.