Bicycle Mechanics - How to install/adjust dura ace 7401rear derailleur
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02-18-12, 02:22 PM
This is my first DA derailleur. It's a 7401 on a steel road bike and I'd like to know how to adjust the screw at the rear that positions the derailleur.
02-18-12, 02:29 PM
Are you refering to the "B" tension screw? most times you never have to touch it.
what other parts are on your bike? some DA RDs do not play well with other shifters
search the net for tutorials on installing rear derailleur (https://www.google.com/search?q=installing+a+rear+derailleur&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a) (links to over a dozen). review a few until you get a decent feel for the job, then pick the one that seems clearest and follow the instructions.
02-18-12, 03:49 PM
Yeah, the B tension screw. I grew up on Campy Nuovo Record and have never seen one of these. I'm going to use the RD in friction mode w/barcons.
02-18-12, 05:26 PM
The basic idea is to back out the screw enough so that the guide pulley comes very close to the largest AND smallest cog, but doesn't contact either.
Depending on the cog set, one "end" may be noticeably further away.
IF for example, you had an "extra large" big cog, the pulley isn't going to be as close to the top cog.
4. How to use the B-tension adjustment screw
Mount the chain on the smallest chainring and the
largest sprocket, and turn the crank arm backward.
Then turn the B-tension adjustment screw to adjust
the guide pulley as close to the sprocket as possible
but not so close that it touches. Next, set the chain to
the smallest sprocket and repeat the above to make
sure that the pulley does not touch the sprocket.
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