Rear Derailleur is...eh... derailed. Ba dum psh!
 

Alright, sorry for the corny joke, just trying to lighten the mood for no particular reason.

Heads up: My rear derailleur is not derailed, I can fix that in a heartbeat :P

I'm having a problem where it won't go to 8th gear (8 sprocket cassette). When the shifter says 8, it's in seventh, when the shifter says 7th, it's in 6th etc etc.

(It's the shimano alivio rear derailleur, I know, horrible, but until my broke teenage butt finds an income of $300, I'm stuck with drivetrain because what sense does it make to fix one part of a broken machine?)

So what happens when you get to 2 and 1? "2" is the "1" sprocket, whereas "1" is half a milimeter (best guess) further towards the chainstay of where "2" is. So, It's never conciouslly registered that even though 8th is 7th, 1 is 1 :(

I've tried tightening the cable, adjusting the set screws or whatever they're called (judging by the fact I can't think of their name may mean I'm adjusting them wrong) and although I can get "1" to be "1," "8" has yet to be "8" no matter how I adjust the screws.

Is there something I'm missing here? Is there something that just blowing right over my head? Or should I just take it down to the LBS and have the payed pros take a look at it. At this point, I see it as my only option.

You should be LOOSENING the cables, not tightening!

Your problem is a comination of bad cable tension, i suggest looseing the cable by using the barrel adjuster and turning it clockwise. With the chain dearilling thats a limit screw issue. To stop it going of the largest sprocket, screw the L screw in, likewise with the smallest sprocket, you will need to fiddle with the H screw.

If thats not it, your hanger may be bent. Look down over the cassette, the deraillure cage should line up parallel.

Just try the above first, it sounds like a classic case of a dodgey un-adjusted deraillure! Visit www.parktool.com.au, and go the repair help section. You will be fixing it in a flash!

:)

You just need to start over.

Turn both your barrel adjusters all the way in (the one at the shifter and the one at the rear derailleur). Then turn them out 1 full turn out.

Then loosen the cable clamp hold the cable at the rear derailleur.

Shift the front into the middle chainring and let the rear derailleur go all the way to the smallest cog. Hit the trigger while slightly tugging at the cable to make sure your shifter is all the way in 1.

Reattach the cable.

While pedaling, shift into 2nd gear. Still while pedalling, use the barrel adjuster at the rear derailleur and turn it out until it starts to "climb" into the third cog. Then turn it back "IN" half turn to a full turn.

This will align your rear derailleur with all your cogs. (assuming your hanger isn't bent).

Shift through all your gears. If it hangs up while shifting to the biggest cog, turn the barrel adjuster out. (Small 1/4 turns at a time)

If it's slow to drop down to the next smallest cog, turn it in. Again, small adjustments.

That should fix it!

Thanks.

Problem is I've found that the cable conduits are fraying and are "in need of replacement."

So I've got to get new cables before I can fix the derailleur, which renders the bike unoperable :(

Well I had that same exact problem with my derailleur so I just said **** it because I don't have much patience and I went single speed. Best decision ever.

Alright. I got some new cable and housing, and a cable cutter, and that's all working great so now I'm working on the derailleur itself.

What do you know, hangers bent. I'm not going to bother and try and fix it, I'll probobly just snap the thing in two and by some unknown teist of fate break my wrist at the same time. Worse and weirder has happened to me...

So I'm just going to see if I can get a free one (or two, three maybe four) from K2. If not, they're pretty cheap.

But going through all this (and the guides provided by blue_neon and a2psyklnut (how exactly do you pronounce that?) have helped alot) was learning and this is not all at waste, even though the hanger is bent it works better then before.

Thanks to all.

Better news yet...hangers are ment to get bent! Hangers are also ment to be straighten! There is only one (1) thing to do...go to the LBS and get them to straighten it for you!

Good luck! And glad you learn't some stuff on the way!