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Old 01-16-10, 07:20 PM   #1
kludgefudge
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Chain skipping on smallest cog and it is NOT a wear issue.

Ok, I have spent the better part of an afternoon trying to correct a skipping chain problem on an old peugeot that I have set up with a first gen shimano freehub with a brand new cassete. the chain doesnt skip or anything at all in any other gear. I tried a new chain and that didn't fix the problem. I threw on a different RD than the crappy simplex (shimano 600...old pre indexed)..that didnt help either. In fact given its lack of b screw adjustment and that I installed it with a random SIS hanger it is tensioning the chain worse than the simplex on the little cog. (and yes, the chain is as short as it can be to work on the big cog. )

This takes us to the casette itsself. it is a seven speed model on a 6 speed body so I installed it without the 6th cog, but with spacers with these casettes, the 7th cog is the lockring. the spacing is the same as between the other cogs The drivetrain functions fine with the wheel from my bianchi, which has an even farther outboard little cog. (yeah, maybe thats telling me somthing)

My theory: as this is a total frankensystem, with nothing exactly right for any other part, I belive the chain is catching momentairily on the 5th cog at the point in my pedalstroke where I am applying maximum force through the drivetrain. this problem only happens when the drivetrain is under load, I cant replicate it on my bike stand.

My plan: add a .5mm spacer I saved from the previous cassette. requires building a 2nd chainwhip or taking it to the LBS: niether of which is happening tonight.

My question: If this doesn't work, are there any other likely explanations for why this is happening? I figured I'd ask now so that in the unfortunate event that a spacer doesnt solve all my problems I might have some other ideas on hand, because this is my last one. It should have been my first.

EDIT I forgot to mention this is a 10 speed to five conversion, with the outer chainwheel ground off, so It is kind of important for the forbidden cross gear combo to be useful.

Last edited by kludgefudge; 01-16-10 at 07:26 PM.
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Old 01-16-10, 07:27 PM   #2
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How 'bout this -- instead of frankensysteming, get the appropriate parts? Not everything is cross-compatible, especially on older systems.

Just sayin.
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Old 01-16-10, 07:39 PM   #3
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Move the chainring outboard to improve the chainline.
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Old 01-16-10, 07:45 PM   #4
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$10 5 speed shimano freewheel. And we're done.
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Old 01-17-10, 04:28 AM   #5
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Those 5 speed shimano freewheels you mention just spin right on to first generation shimano freehub bodies I guess then eh?
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Old 01-17-10, 05:23 AM   #6
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Quote:
Originally Posted by AndrewP View Post
Move the chainring outboard to improve the chainline.
+1
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Old 01-17-10, 06:21 AM   #7
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And stop shifting under heavy pedal load?,,,,BD
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Old 01-17-10, 03:40 PM   #8
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After building the most mickey mouse chainwhip ever and installing a second spacer i have decided that it is the spacers themselves coupled with the 13 tooth small cog that is the issue, pretty sure the chain is riding up onto the spacers. I think i just need another spacer or 2 and then i can install either a 14 or 15 tooth, which i have for this particular body, and the lockring that you use a BB tool to put on.

Oh, by the way its a cottered crankset and I have taken off the outer chainwheel with an angle grinder transforming it into a "beauty ring" or whatever. It looks cool. If it was a reg. style crankset I would allready have moved the small chainring outboard.
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Old 01-17-10, 10:53 PM   #9
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Can you taper or otherwise cut down that last spacer so the chain can't possibly ride on it?

And I know it's a simplistic call but you DID fiddle around with the derrailleur limit screws to ensure that it's not almost catching the teeth in a semi attempt at upshifting, right? Sorry, but I didn't see this in your list of stuff done so I thought I'd mention the obvious....
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Old 01-18-10, 12:27 AM   #10
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Yeah, I did a lot of fiddling with the limit screw, trying it a little farther out/little farther in. I think the bottom line is this is happening on the "top" of the cog. it is a very heavy, clunky kinda skip.

As for filing the spacers , that is just the kind of idea I was looking for. I may end up trying that. I had considered trying to find smaller washers, or filing down the whole spacers, but just filing them on an angle....good thinking.
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Old 01-18-10, 02:33 AM   #11
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Could you post a picture of the cog & spacers in question? For ease of communications, the smallest cog is typically referred to as the 1st one and the largest the 6th or 7th.
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