Bicycle Mechanics - Can a Alivio derailer loose it's tension?

I have an Alivio rear derailer that acts like it has lost it's spring tension in the part that bolts to the hanger, it also has the tension adjustment completely turned in to clear the top chain ring (32 tooth). This doesn't seem right to me, just started doing it recently. I have adjusted everything from step 1, but still have to have the screw turned all the way in to function properly. Any suggestions? Could it be wore out?

Yes, a derailleur can lose tension if a spring breaks. Note that this is an all or nothing proposition. Springs don't get weaker over time, but they do break eventually.

I don't know which spring you're referring to, so you test the idler cage spring by pushing the lower pulley forward to slacken the chain, then letting go and seeing if it takes up the slack.

The in/out return spring is harder to test because cable friction can be affecting it. Shift the bike to high gear while pedaling, and hopefully the RD will spring to the outside. If not, help by pulling it out while pedaling. Now disregard the levers and, while pedaling, shift to a lower gear by pushing the lower body in and then letting go and seeing if it moves back out. If it doesn't, the spring is dead & you need a new derailleur. If it does spring out this way, but not in normal use then the derailleur is fine, and your problem is cable friction, or possibly, but not likely the lever.

As I said, derailleurs don't wear out by losing spring tension, the wear would be in the pivots making for sloppy shifting, but the springs themselves are either as good as new, or dead.

To expound on what FB says, springs also do not weaken over time unless they are stressed past their limits. A spring at rest or even in a stretched state not beyond its normal limits will not wear out even if left in the stretched position for a long time.

Ok, so from what you say the spring shouldn't wear out. Why do I need to turn the adjustment screw all the way in now to clear the largest ring on the cassette all of a sudden?

Ok, so from what you say the spring shouldn't wear out. Why do I need to turn the adjustment screw all the way in now to clear the largest ring on the cassette all of a sudden?

What adjustment screw? If it's the low gear limit, it restricts the RD from shifting inward beyond a set point. Turning it in more will keep the RD from going to low gear, turning it out will allow it to overshift into the spokes. But I suspect you know this and mean that you have to turn it in outlandishly far to prevent overshifting, and that points to a single cause, especially because it's sudden.

Almost certainly, the hanger is bent inward, probably from the bike being dropped. That mover the entire derailleur inboard including the limits which are internal to the derailleur. If you can adjust them so the derailleur still works through the range, you can ride the bike until you have the time to have the hanger straightened (or replaced). OTOH if, even with the limit all the way in, it's possible to overshift past the low gear sprocket then do not ride the bike until the hanger is fixed. Right now you have a simple straightforward repair which won't cost much. If you put the RD into the spokes it will become vastly more expensive.

Are you on the big ring in front? You should adjust this with the front on the small ring. See step 4 under SIS adjustment.

http://bike.shimano.com/media/techdocs/content/cycle/SI/SI_6TD0A/SI-6TD0A-002-00-ENG_v1_m56577569830700120.pdf

Jethro, I'm from Toledo IL. The screw that I'm referring to is not the high-low limit screws. It's the one on the back of the derailer that pushes against the hanger. It moves the linear movement of DR up or down in relationship to the cassette rings(distance of jockey wheels to rings on the cassette). I have been unsuccessful in getting it to work as it did prior to this week, maybe it's just time for a new one.

Yes you're talking about the b tension screw. It adjust's the chain clearance to the rear cassette. I upgraded a Trek 7300 from Alivio to a Deore And have an Alivio in my hands.

Jethro, I'm from Toledo IL.


Toledo? That explains everything!!

OK so I gather that even with the B-screw (that's what it's usually called) all the way in the RD is still riding too high, or close to the cassette.

Remove the rear wheel and take a look at the hanger and derailleur from the left (back) side. On some derailleurs the B-screw is part of a "stop cam" and on others part of the derailleur upper body, but either way it engages a tab on the hanger. If the RD is too far forward with the screw all the way in, it's possible that the stop acm is damaged (if there is one) or more commonly, the RD was mounted poorly and the screw has slipped off the hanger and is trapped between the upper body and hanger.

Looking from the back should confirm this. Then you can usually fix it by loosening the RD mounting bolt, pulling it back so the screw is clear, then remounting it tight with the screw behind the hanger stop tab.

Did you take the Alivio off the bike recently. Does the idler cage rotate freely?

FBinNy and I are on the same page here.

Took it off the bike to clean it up. It's on the bike correctly, the screw is engaging on the hanger like it was before. Did you notice any difference going from Alivio to Deore Jethro?

I changed it out because I went from a 11-32 cassette to a 12-25 cassette and the Alivio was just too loose in the bigger rings. (Just the opposite of your problem) I've learned since then that I should have went to a shorter cage road derailleur as the angle they travel as they move in is flatter to keep the guide pulley in the correct place. The deore is the LX version so it's not too bad but probably wasn't the best choice. Live and learn.