[Jere]

my first question is this, can you have a 8-9 speed derailler on a 7 ring rear cogset until you a ready to buy a new cogset?
second question, i came across a shimano stx-rc derailler in an old box of mtb toys along with an old (probably 2000) lx hub with cogset(8 rings) attached, is it worth it to get this setup onto my bike (otherwise a 7 speed) by getting a new rim and spoking the hub on and then using the stx -rc derailler?, or should i just wait and buy new stuff because it has been sitting in a shed a while and the lx hub seems kinda heavy.
anyone who thinks i should buy new stuff can you help me out with the equivalent to the stx-rc because im not sure but i dont think its made anymore.
third question: do you need to buy a new hub if you want a 8 ring cogset and your hub had a 7 speed on it stock?

 

[singletrack]

my first question is this, can you have a 8-9 speed derailler on a 7 ring rear cogset until you a ready to buy a new cogset?

Yes. Any shimano derailler will work with any number of speeds, provided you've got the appropriate shifter. You can use a 10 year old derailler on a new 9-speed cassette, it'll work fine, maybe better.

second question, i came across a shimano stx-rc derailler in an old box of mtb toys along with an old (probably 2000) lx hub with cogset(8 rings) attached, is it worth it to get this setup onto my bike (otherwise a 7 speed) by getting a new rim and spoking the hub on and then using the stx -rc derailler?,

Having a wheel bult will cost much more than buying new pre-built wheel of similar quality. STX-RC R deraillers that aren't trashed are worth keeping.

or should i just wait and buy new stuff because...the lx hub seems kinda heavy.

Uh, yeah... Next question.

...help me out with the equivalent to the stx-rc because im not sure but i dont think its made anymore.

Not made for quite a while. Deore would be the equivalent now: Cheap stuff that works. Alivio is a good budget choice too.

third question: do you need to buy a new hub if you want a 8 ring cogset and your hub had a 7 speed on it stock?

No. Assuming your 7 speed is shimano, you just need to swap the freehub- And you've got a 8/9 speed freehub on the LX hub you found in the shed.

It's pretty easy on shimano hubs, but you should have a shop do it for you.

 

[bulC]

more info on that last question

No. Assuming your 7 speed is shimano, you just need to swap the freehub- And you've got a 8/9 speed freehub on the LX hub you found in the shed.

Correct, you an replace the old 7-sp. freehub body on the hub with an 8/9sp. body, it'll fit the hub shell. But you will also need a new, longer axle, as 7 sp. hubs have a 130mm locknut dimension, and 8/9 is 135.
I believe you will then also have to redish the rim so it centers between the locknuts, as 8/9sp. freehubs are wider than 7 sp. ones, so you need more dish for it to fit.

 

[dusty]

This is technically true....

but on an old steel frame you can often force the 135mm spaced wheel in, then readjust the derailer limits, put on your new shifters and it might work.