Bicycle Mechanics - Best Rear Derailleur For a 21 Speed Bike?
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05-22-11, 11:50 AM
What is the absolute best rear derailleur one can purchase for a 21 speed bike with Shimano trigger shifters?
My Electra Townie 21 came with Tourney, which did not downshift well. The guy at my LBS said Alivio was basically the only other option, which I bought, but it's noisy as hell. LBS guy claims that you can't install an 8-10 speed derailleur on a 21 speed bike, but I have read bike mags that say it's possible. Same guy said I couldn't put a stiffer crank on the bike, but I did, so I'm wondering if I should find a new bike shop.
Basically, I am just wanting the best shifting and quietest rear derailleur I can find (I can spend about $300-400 on something really nice).
05-22-11, 12:42 PM
any new derailleur will work for you . try oiling the moving points on the derailleur , that should help quit it down a bit . also oil the chain ,it may be dry and that why your shifting is so noisy .
05-22-11, 12:55 PM
Truthfully, I think that most any Shimano derailleur will work but, for the absolute best shifting, you should match the derailleur to the shifter. Here's why:
Shimano makes several different grades of components. The lower end ones use cheaper manufacturing processes and are less precise. To allow for that, the lower end components have a degree of "fuzzy logic" built into them. Lower end shifters, for example will let you overshift just a skosh, to make up for a lightly slopier derailleur. A Dura Ace shifter can't make a Tourney derailleur shift more crisply and a Dura Ace derailleur won't be be at it's best if it's paired with a low end shifter.
That all depends on everything else being in the default mode. On older bikes bent derailleur hangers are common. If your derailleur hanger isn't in the same plane with your cassette, the most precise and expensive components in the world aren't going to shift as quietly as you'd like. Try shifting your bike into a gear combination that makes your derailleur arm point straight down. Now prop your bike up so it's vertical and look at it from the back. If your derailleur arm looks like it's pointing toward the rear wheel - that's it. Get your derailleur hanger straightened and your shifting will quiet down.
05-22-11, 04:34 PM
Thanks for the replies. I have lubricated and calibrated the derailleur properly. It shifts quite easily, accurately, and quietly. The noise issue I have is when just riding along (i.e., not when shifting), the pulley sprockets sound like I have a sewing machine attached to my rear wheel.
If you are willing to upgrade the shifter as well, one of the nicer Shimano mountain bike derailers, such as Deore, would be a good upgrade. If you want to keep the shifter you have now, Alivio would be a good buy.
I suspect the derailer pulley sprockets are just worn out. In order to verify this, spray some WD40 into them. It isn't a permanent fix, but it will make the bike quieter if there is a problem. So lubricate them, and if the noise goes away, you know they are to blame. A set of new pulley sprockets probably costs as much as a new Alivio derailer.
05-22-11, 04:58 PM
It's actually a brand new, out of the box, Alivio derailleur, with noisy sprockets from the very first ride, much noisier than the Tourney which has plastic sprockets. But after 100 miles, it has not gotten any worse.
Would it be possible to put a higher grade of pulley sprocket on the Alivio?
Yeah, but they would cost as much as a new derailleur, so I don't see the point.
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