pbd

My derailleur was set-up properly, everything good, until I crashed.

Bike fell on the right side, scratches on the rear derailleur, and the cable was pulled out of the derailleur completely. I took it straight to the bike shop and let them check the whole bike over and readjust the derailleur. I rode it today, shifting was ok, but I noticed it was not perfect the farther I rode, but the bike is still new so that's to be expected.

I get home and start adjusting the rear derailleur again to get it back to "perfect", only to discover 2 things: 1) the H-limit screw is several full turns looser than where it was before, and 2) the L-limit screw won't tighten far enough to make me feel good about it. As tight as that L-limit will go, I still can't make it give any symptoms of being too tight, so I have no idea of when/if it's tight enough.

So with the H-screw working properly but set much looser than before, and the L-screw set as tight as possible and still not tight enough, I'm thinking the hanger is bent inwards. Am I right? My understand was that the shop checked the hanger alignment since the derailleur was clearly scratched/hit in the crash, but it's likely they didn't if they thought the shifting was ok.

Am I missing something, or would I be right to take it back and have them check the hanger alignment? Anything else it could be?

fietsbob

Local bike shop has a derailleur hanger tool, to check, and tweak the alignment.

gyozadude

You may also want to remove the RD, look inside on the pivot cam that butts up against the set screws and see if a chunk of that has chipped off. Sometimes, a impact can force the RD so far in that the inner cam hits the L-screw and damages the contact point.

Retro Grouch 

That's the first thing that I would do. Try shifting into a gear that makes the derailleur arm point down and look at your bike from the back. If the derailleur arm seems to be pointing toward the rear wheel - that's it. If you have a 9 or 10-speed cassette you probably won't be able to eyeball the hanger alignment accurately enough for the derailleur to index reliably.

w98seeng

If the bike was brought in because of a crash and improper RD function, shouldn't the LBS check his first?

Ian

fietsbob

One would would certainly make it part of the 'why doesn't my clicker click good?'. tests.

pbd

Thanks for all the good info, everyone. I took it by the shop again, and they "looked at it". They basically said it's shifting fine on the stand, tweaked the H-limit screw and sent me on my way after just a minute or 2.

Actually, they messed up the H-limit setting, setting it so the chain was rubbing the 2nd cog when riding on the smallest, but I already turned it back out a 1/4 turn so it would stop rubbing.

Either way, they basically said it was fine and not to worry, but it still doesn't look right to me. It's a 10spd Rival derailleur, and you guys say you can't just eyeball it with such things, but that's what they did, they spent about 1 min total looking at it and didn't check with the alignment tool. It does seem to shift fine in the stand, but it didn't seem to shift as quickly while riding. But my biggest concern is still that darn L-limit screw with no adjustment range left in it.

It still just doesn't look right to me to have the H-limit turned almost all the way out and L-limit turned all the way in with no more adjustment available. Should I trust the dismissive "it's fine"? Or should I go to a different shop that will put the alignment tool on it for me when I ask them to? The tone of the encounter just left a bad taste in my mouth, and wasn't very convincing or reassuring. I just want to be convinced that it's fine and that I'm not going to throw the chain into the spokes on a big hill this weekend because of a bad L-limit setting, and that I won't have a problem in the future.


Be honest with me if I'm worrying over nothing. What would you do?

Retro Grouch 

The bottom line is that you're not comfortable riding the bike the way it is now. I'd find a different shop and specifically say that you want the hanger aligned.

If they tweak the hanger alignment (my guess), that'll probably fix it. If they find the hanger is already in good alignment, at least you'll be able to cross that off of your list of worries.

FBinNY 

Tightening the low limit and simultaneously loosening the high limit (on an RD that used to be adjusted) means that the RD is now farther in then it originally was. It's a classic indicator of a bent hanger. A mechanic that makes these adjustments without some alarm bells going off in his mind is deaf, dumb, and blind, or simply doesn't care.

It doesn't have to be the hanger, the RD itself or the cage could be bent causing similar symptoms, but in any case if a mechanic isn't curious enough to get to the root cause and address it, I'd find a new mechanic.

blamp28

++
Clue one - the customer brings in a scratched bike and says he has been in a crash. Clue two - the mechanic has to make major changes to the high and low limit screws to get it to shift correctly. Even without an advanced degree in Astrophysics, one should be able to hazard a guess that something is bent or broken. The only reason not to look further is if the customer says something along the lines of " is there something quick you can do without charging me anything?" You most likely have a bent hanger or dérailleur or both.

robert schlatte

I recently purchased the Park alignment tool. When I was riding, I could look down and the lower jockey pulley was not aligned with the upper guide pulley. By using the tool I was able gently bend the hanger and align the hanger. The tool essentially works by using the plane of your rear wheel as a reference. The idea is to make the hanger parallel with your rear wheel. Because the hanger is so small there was no way I could tell it was misaligned until I used the tool. From you description, it is inexcusable for the mechanic to ignore the simple step of checking your alignment.

pbd

Yep, this experience cost that shop a lot of good faith they had earned with me.

I took the bike into another shop today. It took the mech there about 30 seconds to spot 2 different problems, and another minute later he had the alignment tool on the hanger without me even having to tell him what I thought the problem was. He was actually surprised the shifting was working as well as it was (a testament to the robustness of the derailleur system itself, I reckon).

It took him about 10 minutes total to re-align the hanger and adjust both derailleurs. Everything looks a lot better. The jockey wheels are aligned better, the limit screw is actually functional now, I'm happy. He also checked over the front derailleur, and adjusted it a bit too. The front didn't have any real problem, but his adjustment definitely made the shift from small to big a lot smoother.

Now if only the first shop had gotten it right. The other sad part is the first bike shop (multiple mistakes) is less than a mile from my house, while the second bike shop (fixed everything) is about 13 miles away. I am lucky to have so many bike shop options in this town though, so I guess I shouldn't complain.

Thanks for the help, all. Excellent advice.