When you bolt a rear derailleur to your bike, generally, the derailleur cage will be outside of the cassette, the smallest cog, or high-gear. If you have a rapid rise rear derailleur, you may see that the derailleur cage is closer to spokes, or low gear (biggest cog), if cable is not attached.
If you have a derailleur that is produced in 2005 or later, and not Shimano, it’s next to impossible that it’s a rapid rise derailleur. These derailleurs are not “invented” by Shimano, but they made them in late 90’s to early 2000’s. Somehow they embraced the idea, and their XT and XTR derailleurs were rapid rise at the time.
However, they disappeared, because nobody liked them. I may be exaggerating, yes, but at least there is quite a lot of hate against them.
Why rapid rise derailleurs were so unpopular ?
Well, if you both used Mac and Windows (or Linux, like me) you know that “scroll” is different. In a Windows or Linux machine, when you scroll the mouse wheel or trackpad down, page scrolls down. On Mac, it’s the opposite. People coming from different OS don’t like the idea. It feels weird. Really weird. I used Mac for a long time, and had to change scroll behaviour: funny thing is, all those 3 OS have very diverse feature sets, quirks or functionality. There are days that I use both 3 because I’m a developer and I do weird stuff, but the only thing bothers me is the scroll direction. Why? Because we have a “muscle memory”. It’s sometimes harder to change your muscle memory, rather than to change your political camp. Not kidding.
Rapid rise derailleurs works the opposite. Not literally.
The ugly thing about rapid rise derailleurs is, if you connect your “normal” shifters to them, levers work in reverse. That’s the primary reason why people hate rapid rise rear derailleurs.
Any advantage of using a rapid rise rear derailleur ?
At least, Shimano thought so. Indeed, it shifts faster to easier gear (bigger sprocket), where it is actually needed, especially in mountain biking. There are 2 reasons for that: You lose more time in a normal derailleur, because when you need to shift to an easier cog, you may be out of power, even to move your bike. Other reason, shifting to bigger sprocket needs more force.
This is also what rapid rise rear derailleurs failed their promise, because the springs were not strong enough to warrant a rapid shift.
Is there a new rapid rise rear derailleur I can buy?
No. At least, not one I know of. And there won’t be any.
Let’s face it; electronic rear derailleurs is the future, so we won’t be discussing about the springs anymore, soon.