SRAM Rival front derailleur throws chain to the outside, even after professional adjustment

Question

TL;DR: if you have a SRAM Rival front derailleur I'd love to know if yours looks "funny" like mine does--it's described in bold.

I have a SRAM Rival groupset (from late 2011), including front derailleur/mech, crankset, and brifters. It all works fine except the front derailleur, which is a nightmare.

The bike is just under two years old. For the first six or eight months (but that included five months of winter), everything was fine. But one day I shifted from the small to the big ring, and it threw the chain right off the outside. It worked sort of OK much of the time for a few months, but maybe one shift out of ten, it would throw the chain (always to the outside). It started to get worse, and I tried adjusting the cable tension and limit screws, all to no avail. If I adjusted a bit farther down, it would never shift to the small ring. Up a bit and it threw off.

I took it to a quite professional cycle shop, and for about $20 they adjusted it. From what I could tell and what they told me, they reoriented the derailleur on the seat tube, moving its rear slightly outward (not sure about height adjustment). It worked fine for a few rides. Then it went back to the way it had been, throwing the chain off.

I kept trying to adjust it myself, but it would either not shift up, or it would throw the chain outside. Or it would sometimes shift properly, but only if the rear was around gear 6 (of 10), and not otherwise.

Now I have read the SRAM manual, watched videos online, followed all the steps from initial installation (including completely removing the clamp, cleaning, and reinstalling). I moved the derailleur down as far as I could without overlapping the big ring teeth. I carefully adjusted everything. And I'm right back where I started: either it won't shift up, or it throws straight off.

There are two things that look strange. First is that the outer plate of the derailleur is not what I would call straight. Rather, it seems to veer inward (toward the bike's centerline) at the back of the cage. That is, the outer plate and inner plate do not appear to be really parallel--but I don't think it was ever any different.

The second weird thing is how the chain throws off the outside. It's like the shift is mostly going OK, but only about one link of chain sits where it should, and then the tendency of the chain to go straight when viewed from the top causes it to just run at the same angle from the small ring to the big one and right onto the crank arm. It's sort of hard to describe this, but when I watch closely while shifting, it's hard to see how it's ever going to work well.

For a number of reasons I wonder if the derailleur is actually broken. But it looks fine, and the shop I took it to last time (which sadly is now across the world from me, or I'd go back) said it was OK. And there was no crash or anything else to cause it in the first place.

I've been fixing my own bikes for two decades. This one has me stuck (and I'm not looking forward to visiting another shop with it, partly because the shops where I live now mostly don't seem that great). Do you think the derailleur is simply broken and needs replacement? How would I even tell?

Finally, some people apparently use Shimano 6800/7800 front derailleurs with SRAM shifters. Some of them claim it works much better. Any thoughts on that? Parts are expensive where I live, so I'm a little hesitant to go buy an Ultegra or Dura-Ace part unless I'm pretty sure it will work.

Answer 1

A few things to check:

• Check the derailleur height to the outer chain ring. Basically, this should be as close as possible without hitting the chainring. Make sure it's well secured to the frame.
• When you adjust the travel, put the bike into the large chainring, small cog and make sure there's no more than about a 1mm of distance between the outer edge of the chain and outside plate of the derailleur.
• Make sure you don't have a bent a tooth on your chain ring.

The only time I've had a chain go over the top of the outer chain ring is when the limit isn't properly set or the outer cage isn't more or less parallel to the chain ring. Remember, to get the derailleur over and outside of the chainring, there has to be enough clearance for the chain to make it.

Answer 2

As Rich mentioned by first action would be to check the derailleur height...

I kept trying to adjust it myself, but it would either not shift up, or it would throw the chain outside. Or it would sometimes shift properly, but only if the rear was around gear 6 (of 10), and not otherwise.

To me, it sounds like the derailleur sits too heigh, or the adjustment of the L-screw has gone wrong.

Try adjusting it yourself once you checked the height of the derailleur... Not all "pro's" are equally good at gear adjustments: http://www.parktool.com/blog/repair-help/front-derailleur-adjustments

Answer 3

Well, I took it to a local bike shop, and they fixed it, seemingly. I will see how it goes in a few months, but for now it works fairly well.

In trying to fix it myself I had moved the derailleur down a bit, so it was exactly 1mm above the big ring. The shop guy moved it back up, and also moved the tail out slightly I think. He also loosened the cable--I didn't think this would make much difference, but according to him the cable was previously too tight and this encouraged the overshooting. And of course he adjusted the high limit screw (that's what he started with too, but that alone was insufficient).

So, notes for next time: moving the cage lower didn't help, loosening cable tension slightly may have, and I think making the tail point slightly outward (away from bike centerline) seems viable. Oh, and I think you need a shaman to get these SRAM FDs working perfectly--next time consider a Shimano Ultegra mech instead, because in two decades with four Shimano bikes I've never seen anything so hard to adjust properly.