front derailleur or chain ????

[gongmech]

Hey all,

 

Got a funny problem. I've set up a new braze on front derailleur 2x10 on my bike.Works great if the bike is turned upside down and i'm shifting gears on the FD, then it swops from 39 chainring to the 24 chainring with no hassles and shifts up perfectly fine.

 

Turn the bike over and ride it and the problems start. It seems when i have the bike the right way, I can change up from the 24 ring to the 39 ring but it refuses to cahange back down to the 39 ring even though i can see the cable is slack.

 

Why is that???

 

I'm wondering if it doesnt have something to do with chain tension?? The chain i installed is the recommended length ie. 2 chainlinks longer than the length of big ring to big ring.

 

Any advice??

[M Hickley]

Maybe a slight adjustment of the limit screws?

[akneethling]

Isn't the maximum difference between chainrings 14teeth? I'm certain I read this somewhere.

[akneethling]

39t are usually paired with 26t chainrings.

[TrackGuy]

Isn't the maximum difference between chainrings 14teeth? I'm certain I read this somewhere.

I have also read something somewhere about the general difference in teeth, but not sure what it was might be onto something here.

 

Maybe just release the cable, and reset your limit screws make sure they are good, make sure that the clearance of your biggest ring and front derailleur is also correct, as in how close the cage of the derailleur is to the ring.

Edited August 12, 2014 by Ruan de Lange

[JXV]

SRAM? If not changing down then either chain too tight or FD not pushing the chain across correctly. Agree with trying limit screw adjustment for the inner limit but also check FD alignment. When upside down chain hangs off top off sprocket under the FD and more easily deflected. When rubber side down the chain hangs a fraction lower and needs a bigger push to deflect it. So look at angle of FD to chainring from above and maybe adjust tail of FD in a fraction. If you are using a directional chain is it mounted the right way around?

Edited August 13, 2014 by JXV

[gongmech]

Yes SRAM x0. Hmmmm directional chain...haven't checked if it is. Hmmm

 

Thanx guys. Got some options to check now

[gongmech]

Oh and sorry it is a 39/26

[Skinnyone]

The height of the outer plate should be no higher than 2mm above the large chainring and it should be parallel to the big ring, once these are spot on it should work fine. too often the FD is too high and the outer plate does not contact the chain in the right place to push it down.

 

It is correct that the gap between the two rings shouldn't be more than 15 teeth but if it is then you would've had problems with it shifting up onto the big ring.

[gongmech]

Thanks but it is a e type bolt on FD, so height is standard and so is parallelness

[Guest Smimby]

Chain length us big on big BUT routed via RD. Then +2 links.

 

SRAM chains are not directional. (Not about xx1, x1) but others ok

 

If it does not go big to small, check your FD, maybe it is bend open ie the other plate us not 90 deg down

 

Post some pics if the stages of trouble shooting.