SRAM wiFli cassette problem

[brit_in_oz]

I just put a new Force wifli medium cage rear mech on my force groupset on shimano RS80 wheels. previously it was running compact/28 cassette with no issue but wanted something bigger for the three peaks. I replaced the chain (1090)and cassette (1050) at the same time and the chainrings are less than 3 months old. i have found no matter how much i adjust the cable tension i either get a noise on the 4th sprocket down, or if i adjust this to run smooth / quiet the 7th-10th have noise. Not as bad as the 4th but still a metallic rub (like the the side plates just rubbing a little). if i adjust this by reducing the tension a fraction then the noise on the 4th returns. Its only the 4th, not the 3rd or 5th, which are all perfect.
I have the B tension adjusted to 6mm as per the SRAM guidelines in the large/large. Even tried adjusting this a bit either way, no change to the noise. I have adjusted the high/low position so all the cluster is traversed perfectly
If i change the wheels to another set with a 26 cassette (Fulcrum 3's) i don't get any noise through the cluster. its driving me crazy as its 1/4 to 1/2 a turn either way fixes one but makes the other worse so i know its not the cassette itself but how the chain is running through it
Could it be the reach mech alignment? its all i can think of it being as everything else seems to be adjusted according to specs and its all new kit.

[Duck!]

You may need to fine tune the high (outer) limit. This sets the derailleur's "resting" position, from which the indexing is calibrated. If it's slightly overshifting & dragging on the next bigger sprocket, you need to drop the limit out a tad.

[brit_in_oz]

Thanks Ducky, will try that tomorrow and see if it helps. How much adjustment should i try , like a fraaction of a screw turn or a half/full rotation?

Forgot to say its an 11-32 cassette i have now

[Duck!]

1/8 to 1/4 turn at a time. You don't want to go too far, otherwise you'll spit the chain off the end of the cassette & jam it against the frame.

[brit_in_oz]

Ok Ducky, no luck i went across the range from just changing down to nearly dropping off, could not detect any change in the noise. Did have a bit of sucsess changing the cassette onto the Fulcrum 3's, the noise is still present on the 4th or 7-10th but i managed to balance it so its better across the range. Putting my 28 back on the RS80's and they didnt seem to create the noise, only the 32 does.

So do you have any more idea, besides the derailleur angle possibility>

[mrjono]

Sorry to resurrect the thread, but did you ever figure the problem out? I've got force on my good bike, and apex on my winter bike. I set both up myself, and recently both have started experiencing the same problems:

1. Shifting up into the 4th sprocket doesn't happen, I need to go up 2 and down 1. Adjusting the cable tension to sort this throws out shifting for all other sprockets.

2. 7th sprocket is noisy - getting the noise to go by adjusting cable tension throws out shifting for all the other gears.

My initial thought is that it must be something that I've done, given they were both setup by me. But my LBS mechanic can't figure out it, he suspects it's time for a new RD on my winter bike. But the force RD has done less than 2000miles since new so I really hope that's not the solution. Having read this I'm confident the limit screws are bang on and the b-screw is as sram instruct it.

The cassette is 11-28 on both (PG1070), with the same chain (PG1051). The Apex RD is long cage, the force RD is short cage.

Any ideas on how to solve this would be welcome!

[trailgumby]

If it's only just started doing this, my experienced bet is dirt contaminated housing causing cable drag. The up two down one to get the next gear is the classic tell-tale.

Replace the housing. Replace the cable to eliminate fraying near the shifter as a possible root cause. Use some grease in the last segment of housing before the rear derailleur in conjunction with the o-ring sealed Shimano end caps.

I use the Royal Purple grease I use to lube the pin races on my Cannondale Lefty MTB forks as that seems to attract grit much less.

[queequeg]

^^^^ I'd start by just replacing the last loop of the housing that goes into the RD. I find this bit gets gummed up and affects shifting the most, so I just snip off a new section of cable housing and leave the inner cable the same unless it shows signs of impending doom.

I replace my inners as required, and the cable housing for the whole bike maybe once a year.