# So, What's the deal? Does the 7900 set have shifting issues?



## Solearas (Nov 6, 2009)

I'm a bicycle mech newb but the two middle (new) 7900 cogs skip and don't
work too well -like they are unionized or somethin. The other cogs work for a living and do well.

The 7900 otherwise is smooth as butta. I like the levers big time too.


Thanks


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## hclignett (Dec 18, 2006)

I would check your hanger first.


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## Solearas (Nov 6, 2009)

Will do a check on that.

The mystery for me is I I'm thinking is how can the hanger be an issue
if the other cogs work? Again, mech newb here.

TIA


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## skygodmatt (May 24, 2005)

It's the quick link. 
I used my 7900 for 3k miles and the quick link began to skip on the middle two then worked it's way to other gears in another 200 miles. What is happening is the quick link is weaker than the other links and it is stretching. Then, it gets hung up a bit in the cog teeth. My chain stretch was only at 50% as measured by the Park tool.

Solution: 
Throw the quick link away and put a 10 speed pin in it's place. Now it works good as new. Who cares about taking their chain off?

Conclusion: 
Quick link is too soft and needs to be discarded.


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## Solearas (Nov 6, 2009)

Thanks.

Would you say the same thing if I said this bike has maybe 50 miles on it?

I could see it with 3k miles, sure.


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## zac (Aug 5, 2005)

Solearas said:


> Thanks.
> 
> Would you say the same thing if I said this bike has maybe 50 miles on it?
> 
> I could see it with 3k miles, sure.


+1 on the quicklink, loose it and install a pin. However, with only 50 miles I would say that you need to adjust your barrel adjuster slightly at the derailleur. On a new bike, cable break-in takes about that long, that is why many shops want to see you again after a month to tweak/readjust things.

Try this: Shift into one of the middle cogs. Then sighting from directly behind your bike, (use one eye) make sure the top jockey pulley is directly inline with the cog above it. If not then you need to make an adjustment. The barrel adjuster moves the RD in the direction it is turned. So if you turn it CCW (to the left) it moves the RD inward to the left, and likewise for CW and to the right. Adjust in 1/4 turns until the pulley aligns with the cog. Now run through the gears up and down in both chainrings. If any lag going from high gear (small cog) to low gear (big cog) then rotate adjuster CCW (to the left) a 1/4 turn. Alternatively, if any lag going from low gear to high gear, then rotate adjuster CW (to the right) a 1/4 turn.

One other thing to try is to put a drop or two of Tri-flow in the jockey pulleys. On a newish derailleur, I have found that they sometimes can be stiff with the factory lube, and need a good couple of hard rides (read that as lots of shifting) to get then moving smoothly and consistently.

I run full 7900 with 7800/7801 cassettes/chains, and don't have any issues whatsoever. However I would suspect that the new 7900 cassette and chain should work perfectly too. Make sure that your chain is installed properly. The 7900 is asymmetric, and can only be installed one way. 

HTH
zac


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## DonDenver (May 30, 2007)

zac said:


> +1 on the quicklink, loose it and install a pin. However, with only 50 miles I would say that you need to adjust your barrel adjuster slightly at the derailleur. On a new bike, cable break-in takes about that long, that is why many shops want to see you again after a month to tweak/readjust things.
> 
> Try this: Shift into one of the middle cogs. Then sighting from directly behind your bike, (use one eye) make sure the top jockey pulley is directly inline with the cog above it. If not then you need to make an adjustment. The barrel adjuster moves the RD in the direction it is turned. So if you turn it CCW (to the left) it moves the RD inward to the left, and likewise for CW and to the right. Adjust in 1/4 turns until the pulley aligns with the cog. Now run through the gears up and down in both chainrings. If any lag going from high gear (small cog) to low gear (big cog) then rotate adjuster CCW (to the left) a 1/4 turn. Alternatively, if any lag going from low gear to high gear, then rotate adjuster CW (to the right) a 1/4 turn.
> 
> ...


:thumbsup: 
Newbie or seasoned; good straightforward review & reminder in plain speak. Thanks.


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