Originally Posted by
wozzzzza
.. new .. about 14 years ago ..about 7 years ago it had a new cassette and chain
OK, at that service interval, assuming regular use, you may well be past the grace period where a chain swap can save you.
Originally Posted by
wozzzzza
..cassette looks worn to buggery, centre crank cog is rooted totally
Sprockets and chainwheels can have all sorts of ramps and cutouts to them to aid with shifting. Unless you have a new one to compare it with, eyeballing wear can be real difficult.
Originally Posted by
wozzzzza
..Yes the cranks are on a square taper.
Then you can't use anything hollowtech, octalink, MegaExo ASO w/o replacing other parts as well.
Originally Posted by
wozzzzza
..Whats the talk about bottom brackets??
The crank you have is also known as a 3-piece crank. It consist of the left arm, right arm, and the bottom bracket. It's the part that connects both arms to each other. Might make more sense if you think of it as the crank axle.
Originally Posted by
wozzzzza
... is that the bearing housing or something??
Kinda-sorta. The part of the bike frame is known as the BB
shell, which the BB screws into. Square-taper BBs can either be cup & cone (and axle), where parts can be individually replaced. Or it can be a cartridge BB, where axle + bearings screw into the BB shell as one unit. When worn, the whole unit is replaced.