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Old 06-30-05, 11:06 AM   #1
Chimera
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Suntour ARX rear derailleur

I have an older model Nishiki International 15 spd with Suntour ARX derailleurs (friction shifters). When pedalled hard (under acceleration, up hills, etc.) the chain would skip off. I replaced the chain, as it was somewhat worn, and it no longer skips off. The problem I have now, is that when in the second smallest cog (and large chainring) the rear derailleur "skips" constantly. Playing with the shifter doesn't seem to help at all, and it doesn't happen in any other gears (yet). This didn't hapen with the old chain, and it is quite annoying as I used that gear frequently. Looking at it while pedalling, it doesn't look like the chain is trying to shift, but the jockey wheels (?) seem to jump forward slightly. Anybody have any ideas as to what to do?
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Old 06-30-05, 11:17 AM   #2
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The other thing I forgot to mention is the orientation of the jockey wheels. As you can see in the photo, the chain does not make contact with the front one. Is this normal?
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Old 06-30-05, 11:19 AM   #3
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This isn't a derailer problem. You have all the symptoms associated with replacing a very worn out chain: Basically, your freewheel is worn out (the gears in the back). Typically the smaller cogs wear out faster, because they're used more and because the smaller cogs have fewer teeth to distribute the wear. I'm guessing that the worn cog is the one that you use most

The old chain wore out, and the old cog wore out to match the old chain, so it didn't skip. But the new UNWORN chain has a slightly different pitch from the worn cog, and it therefore skips. Read the "Chain and Sprocket Wear" section of this article: http://sheldonbrown.com/chains.html

You should replace the whole freewheel. If you don't, the new chain will wear out very quickly. In general your shifting will get worse as the drivetrain continues to wear. The best thing to do is to get a new freewheel. Since you're using friction shifters, you may be able to upgrade to a 7 speed freewheel in the process. That will give you a few extra gears. In any case, you can get modern freewheels (which shift much better anyway) pretty cheap from nashbar.com

You can prevent your drivetrain from wearing out too fast by replacing the chain whenever it elongates by 0.5%. The way to tell is to measure 12 links, and if they're longer than 12-1/16", then replace the chain.

I hope that helps...
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Old 06-30-05, 11:24 AM   #4
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Originally Posted by Chimera
The other thing I forgot to mention is the orientation of the jockey wheels. As you can see in the photo, the chain does not make contact with the front one. Is this normal?
Uhhh, normal? That derailleur's about as far from normal as anything I've ever seen!

Seriously, though, I have no idea how that's supposed to be adjusted, but I assume as you do that all jockey pulleys should make contact with the chain. Are there certain gear positions that they all make contact in, and certain ones that the front one is off? If so, maybe that's just the design of the derailleur and what it was intended to do, for some strange reason. Good luck with that beast!
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Old 06-30-05, 11:36 AM   #5
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Originally Posted by juicemouse
Uhhh, normal? That derailleur's about as far from normal as anything I've ever seen!
I've seen a derailer like that before... I think the idea is that the second pulley makes contact only in certain positions, but I'm not sure.

In any case, chimera's problem is almost certainly not with the derailer
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Old 06-30-05, 11:47 AM   #6
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In any case, chimera's problem is almost certainly not with the derailer
I agree. Totally weird design, though. Isn't the sole function of the lower pulley to provide chain tension?
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Old 06-30-05, 11:55 AM   #7
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I agree. Totally weird design, though. Isn't the sole function of the lower pulley to provide chain tension?
Sure is

I *think* the point of it is that it can wrap up slightly more chain without lengthening the cage... when the cage gets leaned way far towards the back, the extra pulley picks up a bit more slack. Seems kind of silly to me.
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Old 06-30-05, 12:02 PM   #8
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Originally Posted by moxfyre
Sure is

I *think* the point of it is that it can wrap up slightly more chain without lengthening the cage... when the cage gets leaned way far towards the back, the extra pulley picks up a bit more slack. Seems kind of silly to me.
Ah ha! Well that's an interesting idea. Essentially a long cage derailleur without the long cage. I'm thinking this might have made some sense in the days of half-step gearing, as it seems purpose built to allow cross-chaining.
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Old 06-30-05, 01:14 PM   #9
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Thanks for the advice guys.

If I were to change the number of gears, would I not also have to adjust the offset of the wheel as well? I bought this bike used, and I am trying to spend as little as possible on it.
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Old 06-30-05, 01:20 PM   #10
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Originally Posted by Chimera
Thanks for the advice guys.

If I were to change the number of gears, would I not also have to adjust the offset of the wheel as well? I bought this bike used, and I am trying to spend as little as possible on it.
You *might* ... a 6 or 7 speed freewheel is a little wider than a 5 speed freewheel (see http://www.sheldonbrown.com/k7.html#spacing). There was a thread on this recently, and basically the consensus is that some 5 speed wheels have enough room to put on a 6 or 7 speed freewheel as is, some don't and you have to redish the rear wheel (not too hard to learn, but rather tedious).

Try this: Measure the distance between the smallest cog and the dropout. That should help you decide whether you can fit a 6 or 7 speed freewheel as is. Or take it to a shop and ask them to try putting a 7 speed freewheel on. If it works, they'll charge you maybe $20-30 for labor+new freewheel. If not, you'll have to decide whether to redish or just to get a new 5 speed freewheel.

Incidentally, if your bike hasn't been so well maintained, it might be a good time to get the hubs repacked with grease AND redish the rear wheel at the same time. The lube is probably dirty and dry... that'll cause the hub to wear out quickly, and if it breaks you're in for a much bigger expense down the line.

5 speed vs. 7 speed isn't a huge deal, but if you can fit a 6/7 speed freewheel you'll be able to get modern shift ramps which *GREATLY* improve shifting. And you'll get a couple extra gears. And the price of a new freewheel will still only be about $15. I replaced my girlfriend's old 6 speed freewheel with a new 7 speed one, and the shifting has vastly improved.
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Old 06-30-05, 02:06 PM   #11
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Originally Posted by juicemouse
I agree. Totally weird design, though.



I knew it was weird! I have the same "double-pulley" design on my SunTour 6-speed-equipped Miyata. I shortened the chain recently, because it was way too long, and now I've had two near-bad 0 mph crashes because the chain keeps falling off of the chainring. Would this be some other kind of 'worn cog' problem, you think? Do I need to change the freewheel? It's falling off of the front, not the back.

I find the shape/look of the derailler really ugly.

Incidentally, I have another old bike with an APX derailler on it (7-speed), but it doesn't have the "double-pulley" design.

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Old 06-30-05, 03:18 PM   #12
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I knew it was weird! I have the same "double-pulley" design on my SunTour 6-speed-equipped Miyata. I shortened the chain recently, because it was way too long, and now I've had two near-bad 0 mph crashes because the chain keeps falling off of the chainring. Would this be some other kind of 'worn cog' problem, you think? Do I need to change the freewheel? It's falling off of the front, not the back.

I find the shape/look of the derailler really ugly.

Incidentally, I have another old bike with an APX derailler on it (7-speed), but it doesn't have the "double-pulley" design.

I'd replace the derailer... I have an ARX derailer from another year and it's a normal design, it's meant for a double.

The double pulley idea sounds kind of neat, but it must not have been very good in practice since they only made them for a couple years.
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