Front Derailleur Won't Shift Up When Pedaling

[jarelj]

Here's what I have: SRAM Rival shifters with FSA SL-K light carbon compact CX crankset (36/46), SRAM chain and rear cassette. I've been fiddling with the front derailleur for weeks now and can't seem to get it right. Limit screws are set fine, the chain does not jump off either side. When on the service stand, I can shift from small to big ring and back with no problems in any of the rear gears. So I think it's great. Then I put the bike on my indoor trainer and try to shift while pedaling and it's no longer so great. It shifts down just fine, but won't shift up with even moderate pedaling pressure. If I try to shift up while pedaling the chain seems to bind against the inside of the large ring and it clunks and rattles until I let all of the pressure off the pedals and just spin freely, then it shift ups in about 2 rotations. Sometimes it even sucks up the lower chain run into the derailleur cage somehow. I've tried adjusting the cable tension both directions and nothing seems to work. I have the derailleur height set so the cage is as close to the large ring as possible without touching, and the angle is parallel to the large ring as well. I'm out of ideas on what else I can adjust. Could it be a chain length issue or ?? Any ideas would be appreciated.

[JonB]

Quote:Sometimes it even sucks up the lower chain run into the derailleur cage somehow

That's called chain suck. Worn drivetrain there mate, that's your problem.

You need a new chain and possibly a new casette. Watch this video:
http://bikeride.com/chain-wear/

Your chainrings may be worn as well, but what to look for is in that video.

[marcdominic]

I agree with JonB, chain suck is primarily caused by a worn rear cassette or worn front chain rings. Have you recently changed the chain? A chain tends to wear into the worn cassette and sprockets so everything gradually functions normally but when you make a change… Moreover, this is most likely to happen on changing the rear cassette but keeping the same old (worn) chain.

If so this is most likely your problem…

I ought add [edit] that a fully replaced cassette with a brand new chain and worn front chain ring will cause similar issues…

[jarelj]

Sorry, I should have specified all of the components were brand new when I put them on the bike. I did swap the rear cassette out from the original one that came with my Rival group to another of the same model but a wider gear spacing. But the chain, chainrings/crank, derailleur and cassette are brand new.

[Surly LHT]

(02-16-2010, 10:48 AM)jarelj Wrote:  Here's what I have: SRAM Rival shifters with FSA SL-K light carbon compact CX crankset (36/46), SRAM chain and rear cassette. I've been fiddling with the front derailleur for weeks now and can't seem to get it right. Limit screws are set fine, the chain does not jump off either side. When on the service stand, I can shift from small to big ring and back with no problems in any of the rear gears. So I think it's great. Then I put the bike on my indoor trainer and try to shift while pedaling and it's no longer so great. It shifts down just fine, but won't shift up with even moderate pedaling pressure. If I try to shift up while pedaling the chain seems to bind against the inside of the large ring and it clunks and rattles until I let all of the pressure off the pedals and just spin freely, then it shift ups in about 2 rotations. Sometimes it even sucks up the lower chain run into the derailleur cage somehow. I've tried adjusting the cable tension both directions and nothing seems to work. I have the derailleur height set so the cage is as close to the large ring as possible without touching, and the angle is parallel to the large ring as well. I'm out of ideas on what else I can adjust. Could it be a chain length issue or ?? Any ideas would be appreciated.

Don't put it on your indoor trainer next time after you reset it up again take it out and try it it could be the trainer you have it set on if not you would be better off taking it to your LBS and have them take a look at it.

[JohnnyCO]

Check chain for stiff link(s). Also since you switched out your cassette, do you have adequate chainline?

[jarelj]

(02-16-2010, 10:52 PM)Surly LHT Wrote:  Don't put it on your indoor trainer next time after you reset it up again take it out and try it it could be the trainer you have it set on if not you would be better off taking it to your LBS and have them take a look at it.

Wish I could, it's 4 degrees outside right now! Yeah, if I can't get it figured out I'll take it in, but it's bugging me that I can't figure out what's wrong. My last bike with Shimano stuff on it I never had to mess with and it always shifted perfectly. I'm hoping it's possible to get this to work and it's not an incompatibility between the SRAM Rival derailleur and the FSA crankset/BB. I already sold my Rival crankset so I can't put that back on to see if it shifts better with that.

(02-16-2010, 11:14 PM)JohnnyCO Wrote:  Check chain for stiff link(s). Also since you switched out your cassette, do you have adequate chainline?

I don't feel any tight links in the chain. Front chainline is roughly 44cm, hard to get an exact measurement, which I think is about right or at least pretty close. The cassette was originally SRAM PG1070 12-25 and I changed it to a PG1070 11-26, so it's the same model just different cogs.

[marcdominic]

Hey jarelj,

I hope that's 4 degrees Fahrenheit otherwise you should be out! Only joking, it's zero (Celsius) here but that's only 32F...

[jarelj]

(02-17-2010, 04:06 PM)marcdominic Wrote:  Hey jarelj,

I hope that's 4 degrees Fahrenheit otherwise you should be out! Only joking, it's zero (Celsius) here but that's only 32F...

Yup, 4 F, and everything is frozen, no fun to ride in that.

I messed around with this some more yesterday. With the bike sitting on the trainer (Kurt Kinetic), if I release the tension of the rear wheel from the trainer and spin the cranks with my hand it will shift up and down in 1 revolution with no problems. If I put tension on the rear wheel from the trainer and spin the cranks with my hand (so not nearly as much pedal pressure as when I'd be sitting on the bike and pedaling), it will not shift up to the big ring until I ease up on the pedal with my hand. So it's definitely the tension on the top run of the chain that is causing the problem to show up. Just can't figure out what the problem actually is....... very frustrating.

[cyclerUK]

(02-16-2010, 11:14 PM)JohnnyCO Wrote:  Also since you switched out your cassette, do you have adequate chainline?

Switching a cassette won't alter the chainline.
Changing the chainset might.
Initially I would back out the "Hi" stop screw on the front derailleur just to make sure that is not limiting the changer.
Does the new chainset have pick up pins and ramps?
See :- http://www.sheldonbrown.com/gloss_ra-e.html
for explanation. (scroll down a bit).

What chainset did you have originally and was that O.K.?

Also is the chain the right length?

[marcdominic]

Hi Jarel,

This does indeed sound, very frustrating. The issue is obviously only apparent when the chain is under tension. I had a similar (but not quite the same) issue after replacing a rear cassette and chain. The culprit was the front middle chain ring: it was worn. It shifted fine when off the ground but when driven on the road, under pressure, the chain sucked. However, this is not quite the same issue you're experiencing.

From your description about when it's happening and how to avoid it, I agree (top line - you guess because it is the top line of the chain that is re-routed) chain tension appears to be the culprit: but why? I know you said the kit is all new. Could it be your chain cannot flex enough to make the transition to large front because it's too stiff to move in a sideways motion when under pressure? If you can get another chain and try that, that maybe a starting point. You could try adding a link to the chain because that will increase its sideways flexibility - but I know adding links isn't easy!

I'm a physicist (Dr) and I think problems like this are intriguing. We need to use detective work to find out "what's up"...

(Marc) Dominic.

[jarelj]

The original crank/chainrings were SRAM Rival, but I never rode it with those on (even on the trainer) so have nothing to compare to on this bike. Yes, the big ring does have ramps built in, but they don't seem to be helping. The chain is SRAM PG-1090R. I did try loosening the high adjuster, and it has no effect on the shifting performance. I don't know if there's a better way to size the chain, but I checked it with the front on the big ring, rear on the innermost (largest) ring, and the tensioner is pointed down at a 90 degree angle. The only thing I see that doesn't look perfect is the contour of the derailleur cage does not follow the contour of the big chainring. I think the derailleur was made to go with a 53-tooth large chainring, and mine is only a 46 since it a compact cyclocross crankset. There's doesn't seem to be any way to change that without attempting to bend the derailleur, which I'm not too keen on doing.

[Joe_W]

Yeah, this difference might cause problems (though I don't see why it should refuse to work completely). The FD cage is one of the parts that has seen the most tweaking since (in my opinion) it is the most complicated part for shifting (not the mechanism but how do you make it shift crisp and fast and reliable -> get the shape correct). Maybe get a new FD if all fails?

Oh, and I'd say the chain is too long. Check out the article http://bikeride.com/calculate-chain-length/

[cyclerUK]

The only thing I can now suggest is to "toe in" the derailleur.
ie. Just turn it so the back end sticks out slightly. No more than a couple of mm.
*** Make sure that it doesn't catch the crank arm when on the big ring! ***

And also hold the shift lever over until the chain has shifted.
Shift levers very slightly overshift when being moved then drop back when the shifter is let go.

It might be worth trying a different chain depending on which model of Sram you have?

I would also agree with Joe that the chain, from your description, could be too long. But I doubt that would cause your shifting problem. But anything is worth a try?

[Squadra]

I have had this problem too. I have a 2010 REI Squadra originally with a FSA Gossamer Compact Crank. REI switched the FSA Gossamer crank out to a Rival and that made it a lot better.

I also noticed that the outer edge of the FD cage was convex, so I straightened that. Big improvement, but still not perfect. I've just learned that SRAM does not lap and rivet the front of the FD cage like Shimano does. It's a little lighter but not as strong. Look at the front of the cage where the metal almost joins - that's where Shimano uses a rivet. This weakness leads to more problem with the cage bending.

My FD cage is spread out a little more than a new one I was just looking at in the store.

[vas9999]

Funny enough, I have the same problem. The long and short of it is, I believe the SRAM Rival (or Apex, since it is identical) front derailleurs might have a bit of a shifting problem with smaller (46T big ring) cyclocross cranksets. Here is my story:

Recently I've built a brand new bike with the following setup (SRAM Apex):

PG-1050 11-32 cassette
PC-1051 chain
Apex compact 50/34 crankset (same chain rings as Rival/Force)
Apex front and rear derailleurs
SRAM TT500 bar-end shifters

Everything was adjusted well and shifted up and down perfectly. However, after a couple of days I did notice that the 50/34 crankset was not particularly well suited for this bike (commuter) and my style of riding - the 50T was a bit too high, and 34T was a bit too low. So, I've replaced the crankset with the cyclocross version of Apex - 46/38 (truly love the combo, btw - 46/38 front and 11/32 rear, for general commuting), re-adjusted everything, and went riding.

And then I've noticed exactly the same issue as reported by original poster. I've already spent more hours tinkering with the FD than it took me to build this bike from the ground up. This is the same derailleur that worked perfectly with 50/34 crankset. Plus - since my front shifter is bar-end friction, things like trim, etc. are out of the question. Here is what I've noticed so far:

1. shifting under power is far worse than shifting while spinning pedals with a hand
2. shifting "up" 38T->46T works reliably while the chain is on the _smaller_ cogs of the rear cassette, but then 46T->38T hardly shifts at all
3. in opposite to #2, shifting "down" 46T->38T works reliably while the chain is on the _larger_ cogs of the rear cassette, but then 38T->46T does not shift

The only way I can get it to shift every time is by relaxing both upper and lower FD limits, but then I start dropping the chain every 5 minutes

I am at a loss. After reading the thread, I might experiment with chain tension. Any ideas/suggestions are very welcome

[vas9999]

I found it. Amazing. The "b tension" adjustment screw on the _rear_ derailleur was way too tight. Two lessons for me:

1. I used to think, naively, that the tighter the chain is, the better it shifts
2. I would not ever fathom that "b tension" screw on the _rear_ derailler would so severely affect shifting at the _front_ - especially with front chainrings not too far part (46/38)

Anyway, the front shifts like a charm now
I would really like to learn more about the "b tension", if there are any helpful links/info you might have, can you please share?

[bobtravers]

http://www.sheldonbrown.com/derailer-adjustment.html

[yankee]

I have been working on a new build for the past few weeks, Specialized Tricross S-Works with SRAM Force derailleurs and shifters and FSA K-force crank 50/34, cassette is an 11-28 SRAM. Had exact same problem as Jarelj that started this thread. Shifted fine on the stand or without any force applied to rear wheel as soon as resistance hit the chain you could not get the chain to lift up onto the big ring. It would not go with the shifters or by manually pulling the cable it just would not go. I tried everything, changed out parts adjusted everything several times. I have built a dozen bikes and never had this problem. The big difference between this build and all the others is that on the others I used Shimano derailleurs and shifters. This was my first SRAM road build. So I put on a DuraAce front derailleur and guess what it shifts perfect even with the SRAM shifters. I have had great experience with SRAM mountain shifters and derailleurs but something is weird with the SRAM front derailleur. So if anyone is having this problem just swap out the front derailleur and you should be fine.