Destroyed rear derailleur

[quezi]

Hi all, I'm new here

I was riding back home yesterday and managed to completely f*ck up my rear derailleur!

Stopped at some lights, began pedalling once they turned and then there was a huge bang and the chain slipped off. Tried to shift the front derailleur up to get it back on and no luck, it was jammed.
Got off and had a look at it and somehow a part of one of the cogs in the derailleur has snapped clean off, and the derailleur itself is also impressively bent.

Here's some pictures:

I think it's pretty clear I'm going to need a new rear derailleur, and will probably replace the chain at the same time.

Question - my bike is an 8-speed, current derailleur is Shimano Sora. Is it possible to put a 9-speed derailleur on, or will that not work at all?
I've never done anything beyond replacing cables and brakes and adjusting gears - how hard is it to replace the derailleur?

Cheers

 

[HovR]

Welcome to the forums!

To be on the safe side I'd also replace the derailleur hanger if you can get a replacement. In the majority of instances like this that I have dealt with the derailleur hanger snapped a few days/weeks after the accident under normal use, due to the damage from the accident.

Replacing a rear derailleur isn't hard, however there are a few tricks/tips that will make it easier. There are two ways you can fit the chain around the derailleur, and I find the easiest way is to break the chain using a chain tool, loop it around the derailleur cage and then re-join it with a quick link.

Secondly, when you fit the gear cable ensure that both the derailleur and the shifter are in your highest gear, and the cable is pulled reasonably taught. If you have done this, then there should be very little indexing to do - Maybe just tightening the cable a few turns with the cable stop.

Have you indexed gears before?

And yes, a 9 speed rear derailleur should work on your current setup.

 

[quezi]

Cheers Hov

Yeah I've indexed gears before, they've never been perfect but I imagine it's just a case of practising a bit more!

I take it a new rear derailleur wouldn't come supplied with a new hanger then? They're separate pieces?

I'll see if I can track down a suitable one here or on ebay, funds are a bit tight to buy new!

Also, I've been googling and noticed some are described as 'short cage' and others 'long cage'..whats the difference?

 

[mcshroom]

Yes you can use a 9sp sora mech with 8sp (I have on my road bike). The dérailleur isn't indexed so it just does as it is told by the shifter.

To change it, you need to break the chain, unclamp the cable and then unscrew the bolt holding it onto the mech hanger (5mm Allen key). Obviously fitting the new one is the reverse of removing the old one.

You will need to re index the rear gears and set the limit screws for the top and bottom.

 

[HovR]

Cheers Hov

Yeah I've indexed gears before, they've never been perfect but I imagine it's just a case of practising a bit more!

I take it a new rear derailleur wouldn't come supplied with a new hanger then? They're separate pieces?

I'll see if I can track down a suitable one here or on ebay, funds are a bit tight to buy new!

No problem!

When indexing gears the key thing to remember is if the gear change is slow/sluggish changing in to a lower gear, tighten the cable. If the gear change is slow/sluggish when changing in to a higher gear, loosen the cable. Small adjustments at a time, and you'll eventually find that sweet spot of perfect shifting!

No, unfortunately the new rear derailleur wouldn't come supplied with a hanger as most hangers are model or manufacturer specific, so not any one will do.

I can't quite work out what bike you have from the pictures, but say for example it was a Specialized Allez, then do a search for "Specialized Allez derailleur hanger" and you should find one that will work. Either that or take the bike in to a bike shop which deals with the same brand of bike as you have and they should have some.

 

[HLaB]

Question - my bike is an 8-speed, current derailleur is Shimano Sora. Is it possible to put a 9-speed derailleur on, or will that not work at all?

My Sirrus as a 9sp tiagra mech on a 8 sp cassette, it all works fine wit the sifter wit the obvious caveat there's only 8 gears.

 

[HLaB]

Cheers Hov


Also, I've been googling and noticed some are described as 'short cage' and others 'long cage'..whats the difference?

The short cage is just a road bike set up but it can only handle a cassette up to 27or 28t if you want bigger (lower gears) you'll need a long cage.

Edited due to a dodgy keyboard ;-)

 

[quezi]

OK thanks for the help guys.

Another question - while I'm waiting for a new derailleur to be delivered, if I removed the broken old derailleur off the bike and shortened the chain to a certain length, would I be able to use the bike as a sort of fixie? Or would that not work at all?

 

[HovR]

OK thanks for the help guys.

Another question - while I'm waiting for a new derailleur to be delivered, if I removed the broken old derailleur off the bike and shortened the chain to a certain length, would I be able to use the bike as a sort of fixie? Or would that not work at all?

If you could get the chain tension right, then yes that would work - However that is a big if. Many times I have tried this and there isn't a gear combination that will get the chain tension exactly right so the chain will try to change up/down a gear by itself, which is never good.

Worth a try maybe (also, it would be a single speed, not a fixie/fixed gear )