Expected life of a rear dérailleur?

[Mile195]

My bike has done 19'000 miles from new and the rear dérailleur is the only part of the drive train that Ive not replaced. (Shimano 105 compact)

Having recently changed the chain and cleared all the crud out of everywhere else, I find that it shifts "ok" but it's not great. It's not an adjustment issue. When I pedal backwards it shifts down. When I pedal forwards it shifts back the other way, regardless of how well I've adjusted it.

I think it's down to "play" between each segment of the dérailleur. You pedal one way it's fine, pedal backwards and all the segments twist slightly in relation to one another. I think all the grit and grease was actually preventing some of this movement (I've been very slack with cleaning it this year) hence why it's only manifesting itself since the chain change.

My question is: each segment looks to be non serviceable, but is this actually the case? Ie, can I do anything to "tighten up" the play in each segment? Or after 19000 miles and no doubt 10s of thousands of gear changes, is it more likely that it's reached the end of its serviceable life?

Thanks in advance for any help!

 

[howard2107]

Given that they are relatively inexpensive, and the miles you have covered, then i would replace it. These things can be overhauled, but also need to be done properly, and it can be fiddly to do to get it right. Keep the old one and overhaul it at your leisure just for the experience, and then in another 19000 miles you will have one ready to fit.

 

[MichaelO]

Have you ever replaced the jockey wheels? Mine were utterly worn out after about 15,000 miles - changing them made a huge difference

 

[screenman]

Have you checked hanger alignment?

 

[martint235]

Have you ever replaced the jockey wheels? Mine were utterly worn out after about 15,000 miles - changing them made a huge difference

This. I've never had to change a rear mech before but I have changed the jockey wheels a couple of times on different bikes.

 

[Globalti]

Don't waste your money on a new derailleur. The play is not an issue and the pivots are engineered to last. They also get very little wear. If you buy a new one and compare you'll realise that there's no difference. Guess how I know this?

Of far more importance is the quality and age of the jockey wheels. Buy a set of good ones with decent bearings and they will transform the shifting.

Of even greater importance and mostly ignored is the cable, especially the round curve to the derailleur. This is stressed and wears fast especially in wet gritty conditions, and the steel reinforcements inside get rusted up inhibiting performance. Most people don't realise that just replacing that short length of cable will make your shifting like new. Buy a couple of metres of outer and a cable cutter or get your LBS to cut some pieces to the right length and give you a handful of plastic ferrules and cable end caps. Replace the inner once a year, use Shimano cables which are more supple and more slippery than cheap shop cables.

Lastly, get the hanger alignment checked as dropping the bike on its right side can bend this and inhibit performance. Don't bend it too much as it's designed to break sacrificially, to save the frame.

 

[Mile195]

The Jockey wheels have been replaced multiple times. The last BBB set I put in about 8 months ago. The chain I left a bit long this time by rights, but it doesn't look like the jockey wheels have had it just yet as a result.
Gear cable I changed about a year ago so I'd also be surprised if that was done with yet - it was a proper shimano branded one so I would expect a bit more life out of it really.

The hanger is another matter. I had an issue some time ago and thought that was the cause as it HAS been bashed a couple of times in the past. Issue turned out to be something else entirely, but I wasn't aware there was any way of checking them properly. I know you can't really tell by eye. Is there a method to this that I can do in my garage or will my LBS have some kind of fancy laser thing to check it properly?

 

[Dogtrousers]

The hanger is another matter. I had an issue some time ago and thought that was the cause as it HAS been bashed a couple of times in the past. Issue turned out to be something else entirely, but I wasn't aware there was any way of checking them properly. I know you can't really tell by eye. Is there a method to this that I can do in my garage or will my LBS have some kind of fancy laser thing to check it properly?

Your LBS may have one of these. Or something like it.
http://www.parktool.com/product/derailleur-hanger-alignment-gauge-dag-2-2
Or indeed something with lasers and flashing lights, I don't know.
NB I've never seen or used one of these. Just read about them.

 

[summerdays]

Of far more importance is the quality and age of the jockey wheels. Buy a set of good ones with decent bearings and they will transform the shifting.

Any recommendations? I don't know what makes the difference so I would just use price and not pick the cheapest ones. I think the only thing I know is that you have to replace it with the same number of teeth. (Or are they all the same?)

 

[Globalti]

Yes, you can leave the INNER gear cable for a year but the OUTER where it curves round to the derailleur needs changing much more often especially in wet mucky conditions. It's a stressed item and performance drops off fast, causing ghost shifts and all kinds of problems. When you do replace that length of outer cable, smear Vaseline or grease on the ends to keep water out.

Hanger alignment is checked by removing the derailleur and screwing in a rigid bar, which rotates parallel to the wheel and has a movable pointer that touches the wheel rim to check that the wheel axle and the derailleur pivot are exactly parallel,

 

[Globalti]

Any recommendations? I don't know what makes the difference so I would just use price and not pick the cheapest ones. I think the only thing I know is that you have to replace it with the same number of teeth. (Or are they all the same?)

Well the plastic ones are good enough and they run silently but they do wear out quite fast. Recently my LBS had stock of some rather fancy alloy jockey wheels, which were priced at £40. I picked up a set and gasped at the price and the owner said: "You can have them for twenty pounds!" I fitted them and they have improved the shifting a lot, much sharper and more accurate and they are wearing much better than plastic wheels so I reckon they are worth the money, even at £40.

They are all the same size but check whether for 8, 9, 10 or 11 speed.

 

[Milkfloat]

At £25 I would just replace the whole derailleur to save yourself hassle. I would probably replace inner and outer cable too to save the hassle of doing it again in a few months. However, I am part of the 'everything is disposable' generation.

 

[bykeshed]

You say it's not an adjustment issue but in my experience a gear change on back pedal is usually fixed by an adjustment to tighten the cable, sometimes only a minute one, but an adjustment all the same.

If an adjustment makes no difference then I second (or third, or fourth?) the suggestion to change the cable, regardless of it being Shimano. Derailleurs do wear out but tension is usually managed by a combination of cable and chain and you can still get the perfect gear change.

I get more complaints of broken cables from well-known brands than I do non-branded. Like with supermarket value beans - they're the same beans, just a difference name on the label.

 

[Mile195]

Update for anyone who's interested:

Ended up with a bit of knee strain on Friday pushing away in gears that were too high, knowing that changing down would be accompanied by crashing and banging which would annoy me. I don't know what financial value one might put on my knees, but I decided that if I had to give it a value, it would probably be more than £31.99... So based on that I swapped out the derailleur, and cable inners & outers over the weekend regardless of the source of the problem. Spent 15 minutes tuning up the adjustment and now it runs and shifts lovely.

There is definitely less play between each segment of the new derailleur than the old, although perhaps this is one of those issues that has input from multiple sources and the cable did have a part to play too.

I inspected the hanger by eye once I'd taken off the old unit. There wasn't really any sign of straining/cracking/discolouration on the surfaces and it looked "true". While that's not a perfect indicator, the fact it runs fine now implies this didn't have a contribution as it turns out but thank you for the suggestion - definitely worth considering.

I might overhaul the old derailleur when I have a bit of a spare time... Or it might just sit on the shelf until I get bored of looking at it and throw it in the recycling 2 years from now, which seems infinitely more likely... We'll see!

Thanks all for your input anyway. Much appreciated as always!

 

[fossyant]

Probably mucky cables causing issues.