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Cannot properly adjust front derailleur
#1
Hi,

I have cube aim pro 29 with Altus M310 FD. Recently purchased, ready to run.

Thing is I'm not satisfied how the FD is working. There is a problem
with chain rubbing.

For ex. when running in second ring upfront (where in theory there should be no rub at all in any rear shift), there is a rub depending on cable tension.

If I adjust FD in the biggest rear ring, it rubs when I shift to small ones (7,8)
and vice versa. If I adjust in smallest rear ring, it rubs when I shift to biggest (1,2,3). So basically I cannot adjust that no rubbing is present in all rear rings when in second ring upfront.

Also in first ring upront I can ride only biggest four rear rings (1,2,3,4) with no rub. When I shift to 5 rubbing appears.

The height and angle seems OK. Also both limit screws are adjusted according to manuals. Is there anything else I could do???

Ivan
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#2
It is not unusual or wrong to get some rubbing in cross-chain combos. Some shifters have a trim feature which allows you to slightly move the front to avoid rubbing. If you don't have that available there is nothing more to be done. There is overlap in all triples, so the gears that are rubbing probably have a close duplicate in gear ratio on another ring.
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#3
Thanks for the answer.
Maybe I'm too demanding but from all info I'm gettings there should be no rubbing on middle ring upfront especially since the bike is new. I wonder what is the situation on other same model bike. I agree there is close duplicate ratio, but why shifting if I dont have to.

Another thing that crossed my mind is to check the size of cage if its eventually bent. I was searching for dimension but cannot open the shimano techdoc.

Does anybody this documents or dimensions?
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#4
Some shifters have a "trim" function as cny-man mentions. This allows you to adjust the front derailleur a small amount to stop rubbing without moving it enough to cause the chain to shift. If your shifter has this, you need to use it to stop the rubbing.

If your shifting system does not have trim adjustment (some don't), then the most likely candidate is that the angle of the front der. is off. Certainly possible that the der. could be bent or some other issue, but it may be hard to diagnose that from a distance.
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