Improving Sram GX Eagle derailleur with parts from X01

The Sram GX 12-speed Eagle groupset was launched about 1 year after the more premium X01/XX1 offerings, and while gaining a little weight, the performance was advertised to be comparable. Well, it's not! One of the major drawbacks is the rear derailleur, which is considerably less sturdy than the more expensive offerings. You get what you pay for, and the GX still works acceptably well, but with little money it can be made better. While Sram have quietly updated Eagle, there are still features and materials reserved for the 2 high-end Eagle groups.

The mounting bolt is one of the drawbacks. The GX bolt (pictured on the left) is just a plain bolt with a rather loose fit in the derailler body, where as X01 and XX1 (pictured on the right) use a thinner bolt, a plain bearing and a nylon sleeve in the derailleur body, which results in considerably less sideways play in the derailleur. The good news: The X01/XX1 mounting bolt can also be used the GX Eagle derailleur, and while the X01/XX1 Eagle derailleur mounting kit doesn't come with the nylon sleeve found in the more expensive derailleurs, it still fits just as snugly and works very well. You can see the difference in sideways movement in the 2 videos below.

The GX mounting bolt is held in place by the silver circlip you can see in the picture above. Use a small flat head screwdriver to pry it off, remove the old mounting bolt and pop in the X01 bolt with plain bearing! As you can see, there is noticable wear in the GX mounting bolt even after ~500km I've ridden it. It's not sealed like the X01 plain bearing version, so crud apparently gets in between the bolt and the derailleur body causing further stiction.

The kit costs around 23EUR from most online retailers, takes mere minutes to fit and certainly makes the GX shifting more predictable. Play in the mounting bolt is mostly gone with the new X01 plain bearing.