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Old 09-26-12, 08:06 PM   #1
PatrickGSR94
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Rear derailer position at rest with no cable tension

Most RD's I've seen default to the smallest cog when there is no tension (or lowest tension) on the RD shifter cable. Increase tension on the cable (and stretch the RD spring) by pressing the largest lever on trigger-shifters, or moving the brake lever on brifters, usually down-shifts to the larger cogs. Releasing the tension up-shifts to smaller cogs.

This seems backwards to me. It's not backwards from how the FD works, but it's backwards in terms of upshifting (lower cadence, faster speed), or downshifting (higher cadence, lower speed). Indeed after riding for months I still get my rear shifting backwards by hitting one lever when I meant to hit the other from time to time.

But it seems like I saw a video once showing how to adjust an RD that had its default position under the largest cog on the cassette, and increasing cable tension moved the chain to smaller cogs. This would make both levers on both shifters operate the same - large lever (or brake lever) for up shifting, small lever for down shifting. Is there a name or term for each type of RD, one that normally sits closer to the wheel, and one that sits farther away? Have searched Sheldon's site but didn't see anything relating to RD positioning.
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Old 09-26-12, 08:12 PM   #2
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Shimano's Rapid Rise mountain bike RD's use spring tension to move the derailleur towards larger cogs, cable tension is used to move it towards smaller cogs. So the "default" position (no cable tension) is at the largest cog, opposite of conventional RD's.
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Old 09-26-12, 08:15 PM   #3
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The most common derailleur type, which defaults to the smallest cog is a "high normal" one. The other is called "low normal" , trademarked by Shimano as "Rapid Rise". Here is the Sheldon Brown article you were looking for: http://www.sheldonbrown.com/gloss_l.html#lownormal
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Old 09-26-12, 08:16 PM   #4
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Semi-related, I have a backwards thumbshifter made by SR Sakae. Nice shifter but sure threw me off. It has a powershifter style ratchet to it. Seems like it was of a vintage prior to the Rapid Rise stuff...
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Old 09-27-12, 11:50 AM   #5
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Shimano marketed several rear derailleurs in both versions. My hybrid and mtb bike rear derailleurs are all XT low normal derailleurs.
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Old 09-27-12, 12:40 PM   #6
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Not sure if this will help but when I got my first modern bike with STI shifting I was racking my brain trying to remember what I was doing and mixing up shifts etc.

I read a lot of stuff about shifting and nothing seemed to help me with getting it straight in my head.

I started thinking about it and this is how I reconciled it in my mind and it became second nature instantly. If you are looking at the gears on the rear cassette the smallest is to the right and the largest the left. In the front it’s opposite with the chain rings the smallest is the left the largest the right. My shift thought is not about what gear I’m in but that it takes force to push the chain up hill to the bigger gear front and back. The rear gears are controlled by the right hand so pushing the big lever (more power) always moves the chain up the hill of cogs. The left big lever pushes the chain up hill to the bigger chain ring. The small lever (less force) lets the drop down (easy force). Not that I have trouble remembering the rear gears are on the right hand brifter but knowing I’m pushing them to go up makes it an instinct feeling.

With the mental picture of the cone of gears going opposite directions front and back made the way the levers work seem quite correct.
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