Dynasys shifing issue - 2012 Trek RF Elite

[Element36]

Whoops, the crank and rest of drivetrain is OEM SLX M660 3X10 Dyna-Sys Crankset, not what I mention below.
I did not know where to really post this.. but I suspect here is better than the Trek manuf forum.
I have had this to my lbs who did not find the problem. But adjusted it as I had originally done to try to resolve the issue.. but did not. (Largest cog= lowest rear gear)
Originally if I was in the middle ring on the front and third largest cog on the rear.. everyhing was fine. Sometimes I would need to drop to the second largest ring.. but not often. What started to happen is when in the middle on the front and second largest on the rear, the chain would slip down to the smallest ring on the front and sometimes fall off on the inside. I would gear down for a hill and it would happen when under pressure or as things eased off.. near the top of the hill. This makes it difficult to keep your speed. Even though adjusted by the lbs it was still happening, and frustrating. Now this is happening even when in the middle cog and the third largest cog on the rear. Since this is the gear I use most it is making rides less enjoyable. I have only been for 2 or 3 rides since it was at the lbs last. I have been riding the bike since late April 2012. The chain is not stretched to my knowledge, they would have looked at that.. The center sprocket on the front is designed a little beefier to allow you run it mostly in the center. This issue seems to be hit and miss on flats trying to reproduce the issue. More miss that hit. Guaranteed to happen hitting a hill.
So has anyone else experienced this with Shimano Deore M552 10 Speed Triple Chainset 42/32/22.
It took 8 months to show up, I cannot see it being wear I am not that good of a rider. or ride more than maybe once or twice a week.
Hope there is some help out there.

[Wheelman55]

Have the LBS check the alignment of you derailleur hanger. Check the limit screws too. Best of luck. This drive train should run like silk.

[Element36]

The hanger is tougher than the derailleur... It's one of the things they like and one of the things that sold me on the bike. They have seen more derailleurs busted before the hanger would bend. But that was all checked anyway. It does shilft like "silk", other than when you are in the center 32) at the front and lowest 2-3 gears on the rear.
I might go 2-8 while in the middle on the front, but I am not a big cross chainer.
IE 22 on the front 11 rear... or 42 front 36 rear.

[Wheelman55]

Frustrating isn't it? I'm not a professional mechanic...so take my advice for what it's worth. I'm going to suggest that you learn how to set up and adjust the drive train on your own.

Do you have any books that might help you do the adjustments yourself? Both the Park Tool and Lennard Zinn ones are good. Once you dive in to DIY you'll likely find that it's not as hard as it might seem at first blush.

If it was me I would redo the setup on both the FD & RD and check the hanger alignment. Your issue could be as simple as a stretched cable or incorrect toe in of the cage on FD.

No matter how strong your hanger is, they are designed to deform and break before the RD. FWIW...I built up a new high end frame for myself recently with XTR parts and it wouldn't shift well...guess what...the brand new hanger was bent. I put on my spare (I always buy a spare hanger when I get a new frame)...put on the spare and the shifting was perfect.

Shimano has great tech docs that give you step by step instructions as well as precise specs. Google search will lead you to videos that show you how to do the adjustments.

I would also put on a new chain. If you've been riding the same chain for a year it's likely worn. Never assume that the LBS mechanic "checked" everything. Some mechanics are very complete...some are not.

Hope this helps .