"Reverse" rear derailleurs

[twowheels]

I do this thing called Bitsa Bikes : gives people homeless bikes.
I've come across my first donated bike with a "reverse" rear derailleur (my term). Meaning spring tension pulls the chain toward low gear/spokes. As opposed to convention, spring tension pulls the chain toward high gear/frame.
A few questions. What is the perceived advantage? Are specific shifters required? Can regular shifters just be renumbered?
thanks

[darkhorse75]

It's probably a Shimano Rapid Rise derailleur. It's been phased out so I'm guessing there is no real advantage. You can use normal shifters but they will work in reverse i.e pushing with your thumb to get a harder gear and using the finger trigger to get an easier gear.

[ValleyForge]

It was an option on some Shimano RDs. I had a Marin MTB I bought in the UK which had an XT-level RD that did this. I don't recall anything funny about the shifters but it was nearly 20yr ago.

[trailgumby]

It works with their integrated brifters. The idea is you push down with the brake lever to get an easier gear at both ends, and if you bump the thumb paddle or flip the lever up you get an easier gear. Both sides. Wonderfully intuitive and shifting to an easier gear didn't risk grabbing a gobful of front brake by mistake.

I loved the system. The 2010 XT edition was by far the most ergonomic mechanical shifting system I have ever ridden. I used to constantly get RSI in my thumbs on long rides with the regular 3x9 Rapidfire system, especially my left thumb. Never had a problem with RSI with this system. I sold it with my 26er race bike a few years ago. I was devastated when they ceased producing it when they went to 10-speed

Here is what the right brake/rear shifter looked like.



The 2004-2006 edition looked more elegant but the front shifting action isn't nearly as ergonomic, with too much lever stroke. I still have that system on my 26er hardtail. Unfortunately that characteristic sunk the system in a lot of people's eyes and the brilliant 2010 version came too late.

Shimano's 2x10 ergonomics is much better, with a much lighter action, especially if you go with all-Shimano instead of the XT shifter/SRAM X-7 FD bastardised combo my Scalpel was inexplicably specced with when I first got it. And the clutch rear derailleur pretty much eliminates chain slap and dropped chains. So I'm not missing the brifter/rapid rise combo as much as I thought I would these days.

[twowheels]

The RD I got hold of isn't that high end. It is a Shimano RD-C101, along with a grip shift arrangement with a dashboard gear indicator. I guessed the idea was to have the spring assist change down when the going got more difficult.
I've swapped it out already, along with the grip shits.

[Duck!]

Yes, as others above have said, it's a "Rapid Rise" derailleur. The supposed advantage is that if you're freewheel bombing down a hill and approaching a transition into a climb, you can hit the release trigger a couple of times while rolling, and as soon as you start pedalling for the climb the derailleur will get you into a lower gear. How effective it really is on the trail is probably neither here nor there. It doesn't need special shifters, however the numerical indicators my be arse-about if they're arranged for a conventional derailleur.

[bychosis]

along with the grip shits.

Wondering if 'deliberate' typo. I'm not a fan either!