Shimano Acera Derailleurs for the Dummy Cyclist

Acera rear derailleur

It's pretty much our watchword here at the Antisocial Network that you don't ask people to help you solve problems they don't understand, and that if they volunteer advice you should verify with someone you trust. Today's DotD is one such case. According to her bio, we can (probably) trust Lisa Schwalbe with horticultural questions, but in the case of her SportsRec.com post "How to Adjust a Shimao Acera," you may well need some more... informed advice.

We were gratified to note that Schwalbe somehow found the words of the late Sheldon Brown, whose iconic site is the go-to for many of our in-house cycling queries. Lisa's problem, however, seems to be that she 1) didn't read through Sheldon's whole discussion and 2) didn't know when she was too ignorant of cycling to realize she was out of her depth.

Schwalbe started out by using some words she didn't understand (although that intro didn't make the trip from eHow through Healthfully to SportsRec):

"If your bike has been over-shifting or under-shifting, consider adjusting your gears before your next ride."

We'd do more than just "consider," ourselves. Heck, we'd pull over to the side of the road in the middle of the ride to correct the problem! But then we know how to diagnose sloppy shifting and correct it; even while still on the bike.

Schwalbe starts out by having her readers adjust the B-tension screw, a step that most references (including Sheldon) save for installing a new derailleur (Lisa did cite Shimano's technical manual...), explaining that you should,

"Look at the chain and see whether the guide pulley is just clearing the large gear sprocket when you peddle [sic] the bike with your hand. "

Besides the fact that most riders never need to adjust the B-tension, we're loath to take cycling advice from anyone who thinks you "peddle" a bicycle. Be that as it may, Schwalbe then moves on to the limit screws. They're a little more likely to need adjustment, although her instructions are... a tad misleading (and a tad wrong):

"Find the cable barrel adjuster; it is the bolt below the H and L Phillips-head screws. Using your fingers, turn the bolt clockwise one complete turn to give the cable some slack. Inspect the chain. If the chain is perfectly centered on the small gear sprocket, retighten the bolt. "

First off, that's not how you use the limit screws and second, WTF is that "retighten the bolt" stuff? You don't loosen and "retighten" the barrel adjuster; it's not a "bolt." And finally, there's this strange "instruction":

"Watch the chain on the big gear sprocket. If the chain looks as if it is tilting toward the spokes of the wheel, use your screwdriver to turn the L screw using quarter-turns to the right until it is centered." We couldn't figure out that "tilting toward the spokes" stuff at all, but we think Schwalbe harvested it from technical documents intended for a professional technician building a bike. That's very, very, very likely not what the OQ wanted; and certainly isn't correction for "over-shifting or under-shifting." No, what Lisa really should have been talking about is what it says on the Sheldon Brown site about the most likely adjustment, an adjustment Schwalbe barely even mentions:

"The indexing adjustment is the most frequently needed derailer adjustment... If a derailer is correctly adjusted when it is installed, this is the only adjustment that should have to be tweaked later on, to accommodate cable stretch, or when cables are replaced. The indexing adjustment is an adjusting barrel located at one end of a length of cable housing..."

Yeah,; the Acera groupset is indexed; so the barrel adjuster that Lisa gave a passing mention in her "tips" section is, in most cases, the only thing she should have addressed. What a classic Dumbass of the Day post that was.

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