Derailleur Cage straightening......not hanger

[c3024446]

Is it possible to get a good result straightening a derailleur cage? Not taking about the hanger here - that's easy enough to straighten with the correct tool.
Is there a gauge or something you can buy which determines if the cage is bent? Or a way to check that yes, the cage is bent? Because.....

I've got a couple of bent XTRs in my spares box and may soon have an X01 Eagle one.....would be great if I could:

1. Determine that yes, the cage is definitely bent
2. Straighten them so they could get some future use.

Cheers!

 

[Oddjob]

A ruler should be enough to tell that the cage is bent.

Straightening alloy is always a bit of a bodge. The cages are replaceable, see https://www.bike-discount.de/en/shop/spare-parts-453

You can even get carbon fibre ones if you are a true weight weenie https://r2-bike.com/FIBRE-LYTE-Rear-Derailleur-Cage-Carbon-for-Shimano-XTR-M980-Shadow-long-cage.

Sent from my SM-G900I using Tapatalk

 

[c3024446]

Ok cool. Guess I need to also determine if the "bracket axle" is bent too........

 

[The Duckmeister]

Judging cage straightness isn't easy, because they're typically not flat, which makes checking with a straight edge less than optimal. The two pulleys and whatever cassette sprocket you're on should all align. If the derailleur is out of whack the alignment will vary across the cassette as it will twist through its range of movement.

Also check the derailleur body isn't bent & twisted.

The "bracket axle" is unlikely to be bent, but the B-link bracket itself can bend, which will chuck it out of whack, but the out-of-whackness will tend to be more consistent, similar to the effect of a bent hanger.