Ask a Mechanic: Shimano Front Derailleur Trim Set-Up and Adjustment

Liam writes, there seem to be four index positions on my Shimano 105 5800 front shifter. One for each chainring and another two for trim positions. Do I need to take extra steps to account for these trim positions when going through the process of setting up my front derailleur?

Shimano’s new 5800, 6800, and 9000 front derailleur shifters indeed have four positions; low, low trim, top trim, and top position.  Having all these clicks in the shifter can be a little intimidating and confusing, but the set up procedure for the front derailleur isn’t that much different than previous-generation front derailleurs.  When set up properly you will be rewarded with effortless front shifting and a quiet drivetrain in any gear.  Here is how I go about setting them up.

First, make sure the derailleur cage is set 1-3 mm above and parallel to the outer chainring. You may have to loosen the cable fixing bolt to create enough slack to move the derailleur’s position. Once that is set, tighten the derailleur-fixing bolt down to 5-7 Nm. You can use the support bolt to fine tune the angle if it’s slightly off by using a 2mm allen wrench to butt the screw against the frame. Try to get the angle as close as possible without the support bolt, as the bolt is only there to help prevent the front derailleur from flexing.  Next, make sure the chain is in the small chainring and largest cog in the rear.  Now we will set the low limit.  Turn the screw furthest inboard counter clockwise to move the cage inward or clockwise to move it outward.  Set it so the inner cage plate has .5mm of clearance between it and the chain. Release all cable tension from the shifter by clicking the small lever a few times to make sure it is in the low position.  Anchor the cable by loosening the cable fixing bolt, pulling as much slack out of the cable as possible, and tightening the fixing bolt, torqueing it to 6 Nm.

Now we’ll tune for the top trim position, which requires the fine adjustments of a barrel adjuster. Either an inline adjuster or one that is mounted to the down tube as a housing stop is fine. This is where the tuning process differs from previous generation front derailleurs.  In order to set proper cable tension, shift the chain into the outer chainring while leaving the rear derailleur in the largest cog.  Once in the outer ring put the shifter in the top trim position by clicking the small lever once.  Now use the barrel adjuster to set the inner cage plate to .5mm of clearance.  Adding cable tension will move the inner plate closer to the chain while taking it away will move the cage away from the chain.  After setting proper tension on the cable we can set the high or top limit.  Shift the derailleur back to the top position by moving the large lever on the shifter until you hear it lock into position.  Once again Shimano calls for .5mm of clearance, only this time it’s between the outer cage and the chain.  If the chain is rubbing on the outer cage, loosen the outer screw by turning it counter clockwise to allow the derailleur to travel further out.  If there is too much of a gap or the chain is being shifted off the outer chainring you’ll need to move it closer by turning the top limit screw clockwise.  Once that is set you’ll be good to go.  There is no adjustment for the low trim setting.

You may have to do a little fine tuning on the cable tension after a few rides to accommodate for “cable stretch,” especially if you are using new cables and housing.  If that’s the case just go back to the top trim setting and re-adjust the cable tension to get the proper clearance once again.

 

 

2015-12-16T14:24:40-08:00