Trimming Shimano FD-R3000 front derailleur

Question

My front derailleur is a Shimano FD-R3000. I have been trying to adjust it following the ParkTool video at

Basically it seems to be working OK now: the chain is not falling off the front chain wheels, and is shifting quickly to and from both the big and small chain wheel.

My question is really about trimming. On the large chain wheel at the front and the smallest two or three cogs at the back, the chain rubs against the front derailleur. (I have nine cogs at the back.) I understand that I can press lightly on the left hand shifter to trim - this removes the noise.

Then I move to the small chain wheel at the front. There is no noise when in combination with any of the rear cogs, except perhaps when I'm on the largest cog at the back. What is unexpected is that when I click lightly on the shifter now, the front derailleur cage moves - further inboard.

Is there supposed to be trimming on the small cogwheel at all with this front derailleur? And if so, is the low trim position really supposed to be inboard relative to the low position?

I am rather new to road cycling, so hopefully my question is not completely stupid!

Answer 1

Based on my interpretation of the text of the Dealer's Manual for your Sora derailleur, there is only one trim position which is a when after shifting onto the big ring from the small ring, actuation of the small, lever B, will move the derailleur slightly inboard while still aligning the chain to continue on the big wheel. See page 9 of the manual. Now this trim position is meant to be used when you're in the large ring and beginning to shift up the cassette, at some point, usually around the 2nd or 3rd largest sprocket, the increasing chain angle may cause the chain to rub the inside cage of the derailleur making noise. The trim feature kicks the derailleur slightly inboard--enough to stop the noise without actuating a shift off the big ring.

What is suspicious in your case as described is that you experienced noise when in the big ring and moving out on your cassette. This is odd, because if things are in proper alignment, this large ring--smaller sprocket combination should yield a more proper chainline---the chain runs straighter. Therefore, I suspect you need to check the initial alignment of the front derailleur: the outer cage plate should be 1-3mm (and the closer, the better) above the teeth of the big ring and absolutely parallel to it. You should be able to take a hex key or any straight edge and while touching the outside edge of the outer cage plate, the other side of the straight edge should contact the outside of the large chainwheel, laying flat against the two. This is your necessary starting point.

Answer 2

Thanks for your reply! I realise that I should have written:

<< On the large chain wheel at the front and the largest two or three cogs at the back, the chain rubs against the front derailleur. So my high trim position is slightly inboard compared to the high position. >>

I checked and my front left shifter is coded ST-R3000.

When I am riding in the small chain wheel at the front, when I press the front left shifter, I can still move the derailleur cage further inboard with a satisfying click. So my question is:

Is this final shift actually into a low trim position which is further inboard than the low position? Or is it possible that the shifter is actually compatible with a set of three chain rings at the front, despite the fact that I have only two?

Answer 3

Here is Shimano's basic overview of the left (front) STI lever's trimming capabilities. This action becomes necessary when the gear selection creates steepening chain angle relative to the ideal chainline, which is the linear path that intersects the point representing the midpoint of the cassette at the rear and a point on the centerline of the front chainwheel group. In a front triple set-up, this forward point lies within the plane of the middle ring. In a front-double, it lies at the midpoint between the two rings.

This deflection of the running chain off of the chainline can get the chain to come into contact with front derailleurs's cage plates and make noise. Trimming is an abbreviated shift action that moves the derailleur slightly more inboard (low trim) or a bit more outboard (high trim) and away from the running chain. In the shift mechanism of STI, indexed shifters these trim detents are engineered into the shifter. With a friction shifting system, the rider's touch on the lever guides the derailleur away from the running chain. To clarify a statement in my first answer, there are two trim points accessed with either lever A (larger lever and moves the derailleur out board) or lever B (smaller lever and moves the derailleur inboard).