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Due to a number of reasons, I would like to keep my freewheel at all costs (It's a Sachs freewheel, the bike has all sorts of more 'vintage' components, and they're hard to come by). From reading all the related questions, it seemed the solution would be a new chain, and the teeth certainly don't look warn enough (to me at least) to warrant the freewheel needing replacement.

However, with both a brand new 7/8 speed chain, and the older slightly stretched chain (0.140 in stretch over 12 links), the chain rides up as shown on the teeth when torque is applied. It doesn't happen in the highest gears, or when it's upside down and I'm adjusting derailleurs. The chain is also not touching any adjacent gears due to derailleur misadjustment.

Chain on Freewheel

As stated, I will try ANY reasonable options before replacing the freewheel. I've certainly ridden more worn out cogs without this problem. Should I just try a different new chain? Or is this more seriously worn than I judge it to be?

Additional Pictures added on request: Chain Riding Up Backed off Whole Bicycle From underneath

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Not related to your issue, but Is your bike rubber coated? –  Matt Adams May 26 '12 at 13:45
    
It's a GT Frame which I then Herculined - it's a brand of truck-bed liner that's very tough and scratch resistant. I coated my motorcycle in it, and after a 35MPH slide down pavement, I just had to roll a bit more on the slide marks, and you can't tell it was even there. –  Ehryk May 26 '12 at 15:45
    
The smaller cogs do appear to be moderately worn -- I've seen (and ridden) worse, though. –  Daniel R Hicks Jan 26 '13 at 13:44
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3 Answers 3

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The smallest cog appears to be rather badly worn (hard to say for sure without a shot from the side) and the second smallest is sorta worn, but otherwise the cluster doesn't appear to be very worn at all.

I do note that in your shots you have the front on the granny and the rear on the small cog, meaning that your chain tension is very low. One generally should not ride in this configuration, of course, but shift to a larger ring when near the small end of the cluster.

Can't tell if the hanger or derailer is bent -- it kinda seems to be in the bottom shot, but from that angle it's hard to tell. Look straight down at the derailer and cluster, and then straight on from the back, and make sure everything is parallel. (A bike shop has the tools to check this, but you can often see a lot by just looking.)

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I've bent it to be as straight with the cogs as I can, but I'll take it to the bike shop next and have them adjust the hangar as you suggest. –  Ehryk May 24 '12 at 16:57
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Need better pictures to get a clear idea as to what is going on here, but assuming that the chain tension is good and the derailleur spring is okay, I'd check to make sure your derailleur hanger is straight. Especially on older derailleurs, this can allow the chain to be received by the cogs at an angle whereby the cog above and/or cog below can 'trap' the chain.

Checking the hanger is easiest with the right tool, it's a bit pricey ($60 - search on "Park Tool Derailleur Hanger Alignment Gauge - DAG-2") so best bet would be to hit your local bike shop and have them lend a hand.

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Additional pictures added. Do they help? –  Ehryk May 24 '12 at 6:27
    
Some. In the last one you posted, it looks like the chain is in fact coming from the jockey wheels at a bias/angle. I can't really tell if the hanger is bent (best pic for that is the second one), but this is not always super-noticeable by eye anyway. The first thing I would do if this came in our shop would be to check the hanger straightness. You can eyeball it some...the flat edge on the side of the cogs should be parallel with them. –  Ken Hiatt May 24 '12 at 8:05
    
When I look from above, it looks straight with the freewheel until the last jockey and then the chain is bending to go to the innermost chain ring. I've bent it by hand as much as I can tell by eye, and this hasn't worked. I'm going to try @DanielRHicks' suggestion below and have the bike shop use their tool instead of buying one for one use. –  Ehryk May 24 '12 at 16:56
    
If "the chain is bending" on the smallest cog then you may simply not have the stop on the derailer properly adjusted. You should be able to adjust the derailer so that the jockey wheel is centered directly over the cog. –  Daniel R Hicks May 24 '12 at 17:12
    
The jockey closest to the cog is properly adjusted with the stop. After the second jockey, the chain then 'bends' slightly to the inner chain ring (which doesn't happen in the largest chain ring). –  Ehryk May 26 '12 at 15:47
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This chain has offset links, Throw is away, flat linked chain will fall nicely onto the cog. The rounded links here are catching and riding the sides of the cog...Guaranteed.

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