Monday, August 7, 2017

Shimano 105 Derailleurs for Dummies

shimano 105 derailleur body with barrel adjuster and limit screws
Barrel adjuster (yellow) and limit screws (red), Shimano 105
If you've ever put in more than a few miles on a "ten-speed" bicycle (not that any bicycle still has only ten "speeds"), you already know that having a badly adjusted rear derailleur (aka derailer) can take a lot of the fun out of a ride. Consequently, knowing how to fine-tune the little buggers can make your ride more efficient, and that will make it more fun. Derailleurs don't usually get out of adjustment, by the way: instead, shift cables stretch, and the drivetrain must be "tweaked" to allow for that stretch. Just how to do it seems to escape many people, including eHow's Matthew Ferguson, as he amply demonstrated in "How to Adjust a Shimano 105 Rear Derailleur" at

To put it simple, Ferguson, who wrote dozens of bicycle-related articles for Demand Media (including one featured here a few days ago), blew it. The eHow photographer who came along later, some schmuck named Jeffrey Opp, didn't help, either. According to Ferguson,
"The rear derailleur moves the chain between rear sprockets. The derailleur is controlled by a hand shifter, which is connected to the derailleur by a single cable. As the cable stretches with use, response from the derailleur becomes less accurate. Periodically adjusting the derailleur cable restores crisp response and precise shifting."
     Well, Matthew got that much right, although not one of the Antisocial Network cyclists has ever heard of a "hand shifter" before. That's pretty much the last thing Ferguson got right, however, since he immediately launched into a procedure that an occasional cyclist should never perform:
"Locate the cable pinch bolt on the underside of the Shimano 105 derailleur. The pinch bolt attaches the cable to the derailleur... Use a 5 mm Allen key to loosen the pinch bolt. The cable will go slack."
No, you frigging idiot, you only release the cable from the pinch bolt when you're replacing it! The real answer to the question is right there in one of Opp's pictures (shown above): you turn that little knobby thing on the derailleur body -- the barrel adjuster (there is probably another somewhere along the top tube) -- to take up the slack in the cable!

Oh, and by the way... Ferguson never even mentions the most important step in adjusting a rear derailleur, whether it's Shimano, SRAM. or Campagnolo; road bike or mountain bike: no matter what derailleur or component groupset you have, you need to make certain that the limit screws are properly set. If they're not, you may as well walk -- just like our Dumbass of the Day should. If Ferguson actually rode a bike he'd probably end up walking, but we're pretty sure Matthew doesn't...     
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