So I just got a new used bike and after about 40 miles of riding I noticed it isnt consistently shifting from the large chainring to the small chainring. I figure "hey, I'm relatively handy, I'll fix it myself". But no, instead of just slightly adjusting the derailleur and getting it lined up I decide it would be nice to remount the derailleur itself.

After about 3 hours of going insane I can not for the life of me get this thing working. I adjusted the hight to ~2mm above the teeth of the large ring and the cage is pretty much parallel with the chain rings.

I got the lowest gear working and the limit set, but have not been able to get it to stop rubbing the outer wall on the large ring highest gear setting. I tightened the shifter cable after loosening the barrel adjuster and shifting to the smallest gear and now it won't even shift to the large ring.

Can anyone help me out here? I'm about to pull all my hair out over this.

Start over.

Undo the cable, and get the lower limit set with the biggest cog in the rear. Attach the cable so it is tight but not tight enough to change the position of the front derailleur. Try shifting up to the big ring. If it doesn't get up there, try bringing out the upper limit - it might be set to low so you can't even shift it up. Adjust the upper limit so there is enough space between the chain and FD that it doesn't rub when you are in the smallest cog in the rear. If you keep backing out the upper limit and the cage doesn't move, you need more tension on the cable. Release back down to the small ring, undo the cable, and give it some more tension.

Go to:https://www.parktool.com/repair/readhowto.asp?id=110

You need more cable-tension and loosening the outer limit screw. And you DO NOT want the cage parallel to the chainring, but parallel to the CHAIN when you're in the highest gear. Check out the definitive guide to front-derailleur adjustment: https://www.parktool.com/repair/readhowto.asp?id=75

The other thing is to keep in mind that there's no single position on the front-derailleur that'll let you stay in one spot and hit all the rear gears. You'll need to readjust the FD position as you sweep across the rear. On index systems, there's actually TWO positions for the FD over each chainring. Then you "trim" the FD position as you change gears in the rear. So basically, the FD is in position outer-outer when you're in cogs 1-5 in rear. Then you adjust FD to inner-outer position for cogs 6-9 in rear. Then as you shift into small-ring, you use outer-inner position for cogs 2-6. Then then position FD into inner-inner position for cogs 7-10. Basically you chose from one of 4 front-derailleur positions for the two chainrings.

Pretty much tried that and used biketutor and parktool as references. Any advice on how to get the most cable tension? I'm really yanking in it with some pliers and can't seem to get it tight enough ever. Cable is starting to fray so afraid it might be time to change that too

And you DO NOT want the cage parallel to the chainring, but parallel to the CHAIN

+1

First, set the inner stop screw with the chain on the small/big combo. Then, move the chain by hand to the big/small or just eyeball it as close as you can to set the high stop screw.

Now you can proceed to the cable adjustment. Do you have a barrel adjuster? If not, get one. If so, detach the cable from the front derailler and wind the barrel adjuster all the way in. Now attach the cable making it reasonably snug (I always do this by hand so as not to fray the cable). Now, with the FD in the small ring position turn the barrel adjuster one full turn and try shifting into the big ring. If it goes (it likely won't), then just make sure you have clearance when using the big/small combo (may require a little more tension or adjusting the high stop screw). If it does not shift, continue to add tension using full turns to start then slowing down as you get closer (this will be easier with the FD in the small ring position) until it does complete the shift. That's it.

FWIW, some people here manage to set up FD's without the aid of a barrel adjuster. All of my bikes are triples which would be a nightmare to get working without an adjuster (though I managed to do it on my bro-in-law's bike as a temporary thing) but doubles are generally easier. However, if you are destroying cables trying to get enough tension, that's a sure sign you should be using a barrel adjuster.

Use the instructions found at https://www.parktool.com. Do each step in proper sequence leaving nothing out.
It is critical to have all of the cable out of the shifter before attaching the cable to the derailleur.
It should require very little tension of the cable.

Al

Well, I brought it by the guy who sold it to me who has owned/maintained it. Turns out there's a shifter issue and he's going to replace the shifter and I get to go help/learn on Sunday.