Worn out rear derauler???

[zzyzzx]

Is there a way to know for sure if it's worn out?
I am having issues with mine that I can't seem to figure out.

No amount of adjusting seems to fix it either.

Symptoms:
I have trouble getting the chain on the biggest ring in the back.
When I pedal backwards, even a little, like at a traffic light, it binds.

If it matters, it's a vintage 1990 Shimano Exage 7 speed derauler. It has tons of miles on it, as in tens of thousands.

I suspect I need a new one, or to somehow repair this one, although I am not certain yet. If so how to I buy a new one?

Does it have to be a Shimano?
Do the newer ones that have more speeds backwards compatible?

Normally I replace stuff with Shimano 105 parts and they work just fine.

Are rebuild kits available?

I will look tonight to get the numbers off of it, buy it's stuff on a bike that cost me $600 in 1990.

 

[mpvue]

it perhaps is worn out, but I'd be looking at your cable and housing as well as the chain and cogs also. if it can't get up to the low gear, and the limit screw is adjusted properly, maybe your cable is stretched and has too much slack now.
as for the pedaling backwards thing, if you are in a cross chaining situation, it won't be happy doing that.

 

[zzyzzx]

OK, I will check the limit screw and check the cross chaining situation. Chain has been lubed recently, and it does not cross chain when I am using one of the middle cogs in the cassette.

The bike probably has more than 40,000 miles on it and it is the original derailleur. Of course the wheels in the rear derailleur have been changed out many times. Currently I have in the metal ones with real bearings.

 

[stephen9666]

I would also recommend checking the limit screw and the cable tension. Those are two major adjustments that could cause your issues.

But, it could be worn out. That is a lot of miles.

As far as compatibility, some newer derailleurs may work, but I'm not an expert on compatibility. A little poking around on some of the big bike forums may net you an answer. Two I visit are Road Bike Review and Bike Forums.

 

[mpvue]

that's a ton of miles on a basically entry level derailleur; it may have so much play that it can't get all the way up anymore.
when you say 'wheels', you mean the little pulleys in the derailleur? are you running old school bullseye pulleys? these usually didn't work very well on modern index shifting systems, and did not provide any measurable benefit. stock pulleys are fine as long as they spin freely.

 

[zzyzzx]

Originally Posted By: mpvue
when you say 'wheels', you mean the little pulleys in the derailleur?


Yes. I replace those when I replace the chain

 

[zzyzzx]

Originally Posted By: mpvue
that's a ton of miles on a basically entry level derailleur; it may have so much play that it can't get all the way up anymore.


From what I have read I need to check for side to side play and then compare it to a new one yes.

Buy can I replace it with a rear derailer intended to be used on one with more speeds?

 

[stephen9666]

Originally Posted By: zzyzzx
But can I replace it with a rear derailer intended to be used on one with more speeds?


You'll need to do some poking around to find the answer, but Sheldon Brown has some info on this page:
http://sheldonbrown.com/speeds.html

Often, derailers don't care what shifter is pulling them. The actual shifting and amount of pull is controlled by the shifter. But, there are some examples where certain shifters/derailers won't work together.

 

[zzyzzx]

This is what I did:
First I cleaned the chain, with my chain cleaner. Even though the chain was dirty, this had no effect.
Then I found a YouTube video on how to adjust a rear derailleur, specifically this one:
http://www.youtube.com/watch?v=xkGBajG4TPc
Performing the ToyYube adjustments worked, even on my first attempt.

It works just good with the bike not under load, but under load, it still sometimes does not like to go to the biggest ring in the back, but I have to be going up a steep hill. If there is anything questionable left, it's the 7 speed downtube shifter's indexing capability. That and I should probably measure the chain. I did check a new rear derailleur and it had the same amount of side to side play as my old one.

As mpvue had suggested, it was cross-chaining. Knowing what phrase to search for was very helpful.

The Shinamo groupset in question are the high end Exage components 500 level. Almost the same as 105, except the brakes don't have quick release on them.

 

[zzyzzx]

UPDATE:

It was the rear derailer cable! I've broken plenty and usually when I have my suspicians, I can find broken strands on the cable, but this time I didn't so I naturally thought that it was something else. It wasn't. I was riding Monday evening when all of a sudden the cable was a lot longer than it was supposed to be and I found a broken strand.