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Today we're going to show you how to adjust the rear derailleur. We'll be working with two adjusters: the limit screws and the barrel adjuster. First the limit screws. The thing to know about these limit screws is that they actually do what the name implies that they do; they determine how far sideways this derailleur moves. Now the low screw determines how far it moves inboard, which is the low gear, and the high screw affects the high gear, or how far the derailleur moves outboard. Let's turn it and I'll show you what it does. When we turn it in, you'll notice that that pulley moves inboard, and when we let it out of course it moves the other way. Okay, let's do a real live adjustment. Notice how this bike shifts. We've set it up so it's a little slow to shift into the smaller cog, which is the high gear. We want to alleviate that by adjusting the high gear limit screw. We'll let this screw out a little bit and it will allow the derailleur to move a little farther outboard and carry the chain with it, and it'll shift a little more crisply. Now we've set up the derailleur so that it won't shift into the low gear, or big cog. Just like we did with the high gears, we'll let the low gear screw out a little, and the derailleur will move farther inboard, carrying the chain with it, and onto the big cog. Now here we've set up a scenario where the derailleur moves too far inboard. The problem here is that if the derailleur moves too far inboard, it will overshoot the cog and throw the chain into the spokes. So we'll prevent that problem by turning the low gear screw in. This will stop, or limit, the inboard travel of the derailleur and prevent it from throwing the chain off. You'll notice that when the screw is properly set, the top pulley on the derailleur will be directly below the center of the big cog. That's how you know when you've got the adjustment right. Okay, so let's go to part two of our discussion which has to do with the barrel adjuster. The barrel adjuster affects any shifting problems that are going on in the middle range of the cassette. Here's how it's supposed to look when it's shifting right. You run through the gears and see if it shifts crisply going down the range as well as up. And you'll notice if you have problems because either itll hesitate to shift or it'll shift more than one cog at a time. Okay, here's another scenario. Watch how the shifting is hesitant as it goes from the smallest to the next biggest cog. That's an indication that there's not quite enough tension on that cable. We'll check it through the whole range and see how it behaves. Well, we can see we need an adjustment, and we'll make it on this barrel adjuster. We'll add tension to the cable by turning the barrel adjuster counterclockwise. And then we'll check the shifting again. And notice we'll check it on the low gear range as well as the high one. And when we have the adjustment right, it'll shift crisply through the range both going up and going down. And here's our final check. We want to be sure that these pulley wheels are aligned with the cog that the chain is on. When the adjustment is right, that'll align in high gear, it'll align in the middle gear, and that pulley will align with the biggest cog which is the low gear. And when you've got those all squared away, you've got your adjustment.
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Coffeeclub 
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29 ม.ค. 54 12:34:49
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