New Derailleur

HillofBadgers

I have a touring bike, on the way to work this morning I wanted to get into first gear but the chain slipped off into the space between the wheel and the cassette, this made the derailleur spin with the wheel. It sort off exploded and bits flew off.

I'm wondering how much should a mid range derailleur cost and if it's simple enough to change one so that someone with basic mechanics knowledge can do it or should I just lug it down to the bike shop and if so what's a reasonable price for that job??
Any help appreciated to help me get back on the bike ASAP.

Lumen

It's pretty easy to change a derailleur. You'll need to split and re-join the chain, and tweak the limit screws and cable tension, but it's all straightforward enough - plenty of tutorials on the web (e.g. Park Tools website) to explain things.

HillofBadgers

Thanks, I think the whole reason for this happening is that last week when I was pumping up the tyre, the bike fell onto the derailleur and the limit screws were moved.

Chain's getting old too so might just be better off changing that as well.

AstraMonti

HillofBadgers wrote: »

Thanks, I think the whole reason for this happening is that last week when I was pumping up the tyre, the bike fell onto the derailleur and the limit screws were moved.

Chain's getting old too so might just be better off changing that as well.

Check the condition of the cassette as well, if it's really bad it can damage your new chain.

doozerie

Further to what Lumen says, yes it is straightforward but a couple of other points:

* assuming the new derailleur has the same short/long cage as the previous one then the same chain should work, otherwise you may need to either shorten the chain or buy a new one if you need a longer chain.
* if the current chain will work, you can avoid splitting the chain by removing one of the derailleur jockey wheels and re-fit it "around" the chain. Only necessary if you don't have a chain splitter or if you really don't want to split the chain (e.g. you don't have a new pin for those chains where you shouldn't/can't re-use an old pin, or where you are tightly limited on the number of times you can safely split and re-join the chain (Campag 11-speed chains only, as far as I am aware, though there may well be others too)) - in either of these cases you'll have to remove a jockey wheel to remove the old derailleur too.
* the other adjustment needed on a rear derailleur is to set the distance from the upper jockey wheel to the cassette once the derailleur is fitted, using an adjustment screw on the derailleur. Again it's a simple step but an important one to not forget.

Lastly, if the chain itself was damaged (twisted or bent links) in this incident then you should consider replacing it regardless, and if replacing the chain then you should also consider replacing the cassette depending on how worn it is.

funkyjebus

sorry to hijack the thread (didnt want to start 2 derailleur posts today)

I am upgrading to ultegra on my bike and just need the front derailleur and chain. im going sl so was looking at this.

http://www.chainreactioncycles.com/Models.aspx?ModelID=28282

my question is what does 15t capacity mean? i will be running a standard chainset with 12/24. will this suffice?

Thanks.

Lumen

funkyjebus wrote: »

my question is what does 15t capacity mean?

Sheldon says...

Derailleurs usually are rated in terms of "tooth difference capacity," a number that represents the derailleur's capa city to take up slack in the chain. To find the minimum tooth difference capacity needed for the gearing you have se lected, subtract the number of teeth on your smallest rear sprocket from the number of teeth on the largest. Do the same for the front sprockets, and add the two numbers. For example, if your rear sprockets run from 14 to 26 teeth, the rear difference is 12. If your chainwheels are 36-52, the front difference is 16. Ad ding the figures for front and rear, we get a total difference of 28 teeth. If you get a derailleur with a 28-tooth capacity or inore, it should handle the range. If you use a derailleur with insufficient tooth difference capacity, the chain will be too slack in some gears or too tight in others and you probably will not be able to get it to shift properly.

I can't believe he used the term "Derailleurs". Must have been having an off day.

edit: "This dates back to before I learned how to spell "derailer." Ah, that's explains it.

funkyjebus

thanks lumen. working that out i get 27. 14 on the front. so im good to order. thats what i thought, but always nice to get confirmation.

cheers