Are rear derailleur universal?

PiKe

PiKe

PiKe

Caporegime
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I inherited a bike which was a bit beat up and unloved.

The rear derailleur high low limit screw has been physically bent and it was a swine to get out, I only have one screw now which means the chain can fall off the smallest cog, are these screws universal or failing that, can the derailleur be replaced with any other, or is the teeth spacing/count specific?
 
Pics would help, but if the derailleurs a bit beaten up it's probably worth replacing the whole unit as it probably won't change gear well.

Do you know what model it is?


SRAM and Shimano rear derailleurs for example have different cable pull ratios when shifting gear, so you'd need to use the same make, generally speaking, and if its 9 speed or 7 speed, you'd need to consider that too.

H & L limit screws are generally quite standard so you could remove the good one to measure and potentially buy another IF the rest of the derailleur is in good shape, including the hangar, which is the bracket that connects the derailleur to the frame - this needs not to be damaged/bent/twisted too, or you'll never get a good gear shift.

There's generally 3 screws on rear derailleurs, H & L to stop the chain from drooping off either side, and a longer B screw which is used to adjust how close to the cassette the derailleur sits.

Again pics would help - assuming its a cheap derailleur and not in the best of condition, it could be far less effort to just replace the whole unit.

Hope that helps
 
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The brand is just "Power" and there isn't a derailleur bracket, it seems to be part of the frame.

I can't see a third adjustment screw either.

Don't really want to spend a lot on it as it's pretty rusty but still.rides ok.



 
Wow that is vintage! 6 speed?
it looks like the hangar is integral to the derailleur, and bolted to the frame.

I'm not really sure to be honest - all I can suggest is to point you here: https://forum.cyclinguk.org/viewforum.php?f=5&sid=79e737099427d5530b202b2c5b53a6cc

I'd ask there, helpful crowd and some of them have encyclopedic knowledge of this kind of thing. It might be you can just source a new screw if the threads aren't damaged.
 
If it still shifts fine, you could just tune the gears to either run 1 higher, or 1 lower gear than the corresponding shifter/lever. So you'll either lose one higher or one lower gear. No way i'd spend any money on a bike like that. Maybe some teflon spray and new cable inners, and rubber, but that's it.
A decent bike shop will tell you the same. You could get plenty of generic spares from bikes at the tip, skips, or bike rescue places.
 
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