hkboy313

heya!

current setup.
sram rival front and rear derailleur
sram compact crank
sram 12-27 cassette
kmc chain

i was at the bike shop recently and everything seemed to shift perfect.

maybe im shifting incorrectly. but i noticed if im in small ring but middle"ish" in the front der doesnt want to throw the chain on big ring. on some rare occasions it has worked but after this test run and one dropped chain im hesitate...its not much a problem when shifting up front when im on small cogs in the back though. i rode on hilly terrain however on flats, this is when it dropped while shifting up front.

please advise on a correct shift method. in small ring i shift up big ring, then 2 up in the back? i've read this before but i guess with more experience in shifting and practice it will help?

is this common for compact cranks? also should i get the sram f/d that is equipped or comes with a chaindrop guard?

its a pain in the butt. i swapped out my standard crank for this compact, and all these problems arise....ugh

thank you for any advice guys/gals!

FBinNY 

First of all let's eliminate you as the problem. Upshifting the front requires easing up on the pedals to near zero force. That's because chain tension pulls the chain down so you're fighting it if you try to upshift under load. When ready to upshift, keep pedaling but at zero force, just keep turning the pedals.

So try riding that way a while and see if all is OK. If not, it's time to adjust the FD.

1- set the inner and outer limits as follows. Shift the front to the inner. Check that the FD cable is slack, then shift the rear to the inner and (if necessary) adjust the inner limit so the inside cage plate just clears the chain. (odds are this is OK already).
2- set the outer limit. Leave the lever in low, and shift the FD by pulling the cable away from the frame. Loosen the outer limit trial and error, until you;re able to dump the chain over the outside of the large chain ring. No bring the limit back in by degrees until you 100% reliable cannot dump the chain, no matter how hard you try (still by pulling the cable directly)
3- Now, that the inner and outer limits are properly set, adjust shifting and trim via the cable. This is much easier if you have an inline barrel adjuster, but maybe it's already OK. The right adjustment allows crisp up and down shifts, and trims the cage on the outer ring so the outer plate just clears the chain in high.
4- It's possible that downshifting may be a bit sluggish, so feel free to back off the inner limit bit, but do not adjust the outer limit.

cny-bikeman

**Be aware that the front derailleur must be in the proper position - height above outer chainring and parallel to it if adjustments are to be successful.

FBinNY 

+1.

I bypassed this step because the OP said it all checked out OK at the bike shop. IME - it's very common for shops to adjust trim and.or the outer limit such that the FD will upshift on the stand, but not quite out in the real world.

I see both trim adjusted a bit inboard, and trim adjusted outboard with the limit then tightened to force the cage back. Both cause poor upshifts, and the latter also causes excess cable tension and downshifts with a snap action that causes chain drop beyond the inner.

This is why I emphasize adjusting the outer (High) limit as far outboard as possible while eliminating overshift. This ensures that the limit is not in play during normal shifting which should depend 100% of the cable.