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Old 07-22-09, 10:45 PM   #1
sunstealth
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chain skip only in "large" gear under any load

So i have this problem that is driving me mad. I had a wheel with a 7 speed freewheel, unfortunately it went fubar due to my sister backing her car in the bike.

bought a nearly new sun CR-18 wheel with a 7 speed cassete on it. The said cassette is a shimano unit, looks pretty much new to me a little bit on use on it, maybe at most 200 kilometres on it. (was bought from a reputable shop and i know the mech who's in charge)

The problem is ever since i installed this wheel, it skips gear 6&7 at pretty much every pedal pressure/stroke i apply.

I have a brand new shimano chain hg-70 or something like that.

could it be those 2 cogs are a bit worn and the chain is sliding on it ?
chain is too loose and i dont have enought wrap around on those cogs ?

the derailleur is a low end shimano but always did it's job greatly up to now

can separate cogs be bought and replaced or is it better to change the whole cassette assemble ? (with a sram maybe ?)

can i use a "speed link" like the kmc or sram master/power link on a shimano chain ? the damn shimano pins are 8$ each a "speed link" is 3$

thank you for the upcomming answers and solutions

Mario!
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Old 07-22-09, 11:17 PM   #2
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Any 7- or 8-speed chain should work with your 7-speed cassette. I would not recommend using SRAM or KMC power link on a Shimano chain, but SRAM and KMC 8-speed chains on a 7-speed Shimano system should work fine.

Seeing as everything is fairly new, I'm suspecting the chain is too long. I'm a "long chain" advocate, so my method to measuring a chain is to break it so the chain doesn't rub on itself passing through the rear cage when shifted to the small-small cog combination. The head mechanic where I work is a "short chain" advocate, and his method is to shift to the large-large combination and break the chain so it makes an almost straight line through the rear derailleur. You might want to just split the difference.
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Old 07-22-09, 11:24 PM   #3
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Pfft.

KMC quicklinks will work fine on shimano 6/7/8 speed chains. If the OP has checked for a stiff/twisted link and the hanger is not bent, and is not ghost shifting then the only reasonable explanation is that the used chain is incompatible with the used cogset.

Not surprising.
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Old 07-23-09, 12:02 AM   #4
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so maybe the shimano chain and cassette are not compatible or the chain's too long

btw operator your signature means nothing at all (former quebec french guy here)
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Old 07-23-09, 09:20 AM   #5
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I doubt your problem is due to a worn cogset. If that were the case, I'd expect it to skip in the smaller cogs that had fewer teeth engaged.

Since the problem originated with the installation of the new wheel, I'd suspect the rear derailleur adjustment. If that doesn't do the trick, I'd check the derailleur hanger alignment.
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Old 07-23-09, 11:22 AM   #6
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no amount of adjustment seem to be fixing the issue and the derailleur hanger is straight as an arrow,it is in fact a part of the frame, not a removable hanger.

I think i will try to get a new cassette and remove a link from the chain to fix the issue.!
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