Bought a bike used, it was shipped. I'm thinking the rear derailleur or hangar was bent during shipping, but this is my first geared bike in a long time, so I don't really know...

Tried setting low limit screw as tight as possible with cable just tight enough to get it to shift down. The low limit screw doesn't actually stop tightening. It just gets to a point where it spins and does nothing. Even with the screw as tight as possible the derailleur tries to throw the chain into the spokes, and the bottom pulley actually touches the spokes.

Is something bent? Is the derailleur trashed? LBS fixable only or can I do it? Pics follow:





This is the best way I could think to show the alignment. The shifter is in the lowest gear, the cable is just tight enough to get the chain to move across the cassette, and the low limit screw is as far in as possible. I can take pictures from different angles if it helps.

Thanks for looking.

2nd pic, looks bent to me.
You'll need a derailer hanger alignment tool to fix it. Cheaper to have LBS do it unless you plan on using such a tool often.

The face of the hanger must be parallel to the rear wheel plane for the RD to work properly. While there might be some issues of camera angle, it seems fairly clear that the hanger is pushed in at the bottom.

Even if you could adjust the limits to accommodate the RD position, you'll never gt good shifting because the RD cage is at an angle to the cassette.

Squaring a hanger requires a special tool, so it's your call whether you invest $50.00 or so or let the local shop do it for you for $10-15.00.

If you're skilled, you can also do the job with a 10x1 bolt, and a tri-square and ruler. It's slower than with the tool, but workable.

+1, Park make a specific tool for this, but for the amount of use a home mechanic would get out of it; it's not worth buying, it's cheaper to go to an LBS for them to fix it

Thanks

I went through this with my LBS's mechanic and he wanted $50 for this since he called it frame work. Needless to say, I got the tool. its a 5-15 minute job for a novice.

So check the LBS cost vs tool cost. I have now checked the alignment on all my bikes.

He's nuts. We do this as part of a $59 basic tune, and $10-15 add-on to a rear derailleur adjustment. Shops like this are a boon to home mechanics.

Thanks guys. LBS did it for free because they're super awesome. I adjusted the RD, and it's working flawlessly. Thanks again!