Spld cyclist

I'm having a situation where I can't find a combination of FD position and cable adjustment that results in good shifting. In a nutshell, how well it shifts depends on the rear cog position. If the FD is adjusted so that it shifts well when the RD is in the low end of the cassette (i.e. larger cogs), then the FD dumps the chain off the outside every time that the RD is on the high end of the cassette. If I adjust the FD so it doesn't dump the chain when the RD is on a small cog, then the FD won't make the shift at all when the RD is on a large cog.

Details:

- SRAM Apex FD, RD, and 10-speed brifters. Bike was new in 2012.

- Shifting was excellent in all gear combinations from when the bike was new until recently, then it got a bit worse.

- It was time to replace the chain (this was the 2nd chain that had been on the bike). Also replaced the cassette and small front chainring with SRAM parts (the chainring still worked without skippping, but it was showing some wear and the replacement wasn't expensive, so I replaced it). Shifting was about the same after all that. Not great, but still basically worked.

- It was on its original shifter cables, so I decided to replace cables with Jagwire slick stainless and housings with Jagwire Teflon-lined at about 4,300 miles. Used the exact same length of housing, routed the same way.

- Before doing anything else, I decided to "start over" with derailleur installation. (Probably should have just hooked the new cable up to the FD as-is in the last "known good" setup, but I didn't....). Set the FD a little closer to the large chainring - probably 1 mm. Checked/adjusted limit screws. Then shifting got really bad.

- Lubricated pivots, so FD moves smoothly.

- I believe the cable is anchored correctly. It goes over the little metal "ear" and then into the groove under the anchor bolt.

- Played around with positioning. It shifts a lot better with the FD 3 mm from the large chainring, but it's still a problem. Adjusting the FD so the tail is a little closer to the bike (rather than parallel to the chainring) helped a little bit. Played a lot with cable adjustment barrel.

- Other information: When I replaced the chainring, I tightened the crankset to the correct torque. I can't feel any play that would let the chainrings move relative to the FD position. I did read that such play can cause shifting problems, but I don't think that's the issue here. I think I also reinstalled the chainrings oriented correctly.

- The FD doesn't look mangled and I don't recall doing anything that would damage it. I haven't had it off the bike for a really close look, however.

What am I missing here?

Andrew R Stewart 

That SRAM ft shifting isn't up to the other company's standards? Andy.

Spld cyclist

Previously better than that other company, now worse.

Kopsis

I don't think there's any "indexing" on the small chainring (there is on the big), but there is definitely and "inside" and "outside". Are you sure you installed it in the right orientation?

My experience has been that if I follow SRAM's FD installation guide exactly, it takes very little adjustment to get proper shifting.

Spld cyclist

I can check that. I'm thinking the bolt holes on chainring were countersunk so that I couldn't screw it up (I'm sure the large chainring does have them, can't quite remember if the small one does. It's been a few weeks.). I'm sure I tried not to screw that up, but maybe I did anyway.

Spld cyclist

I was just thinking that I have a 9-speed Tiagra triple FD in the parts box. I could throw it on there temporarily, and see if it works any better (perhaps revealing if the present FD is the problem). Or is it unlikely that the Tiagra would work well anyway?

Kopsis

With indexed shifting, the cable pull of the FD has to exactly match the shifter. A Shimano triple isn't likely to be anywhere close to a SRAM double.

The countersunk side of the chainring bolt holes should face away from the spider, so it sounds like you probably have it on correctly. I assume you didn't go to a different chainring size as part of the swap?

Another likely candidate for this kind of shifting problem is cable issues. Cable kinks or housing problems can make it very difficult to dial in FD shifting.