Curing chain drop on upshift

RichR2

Every now and then while shifting from small to large crank, the chain drops off to the outside.
The groupset is Sram force with a compact crankset and 11-28 cassette. I’ve followed the Sram guidance on setting up the front derailleur and have tried switching chains from a Sram PC1091R to a KMC X10L (both set to correct length) but still get occasional drops. I’m riding a sportive with a group this weekend and don’t really want to drop and be dropped.
Anyone else experience this? Or more importantly have any suggestions. Thanks in advance

ride_whenever

wind your high limit screw in a bit, or possibly a little less cable tension.

RichR2

Unfortunately I've tried both without success. Thanks anyway.

bruce225

Getting similar problems on my the front of my Sram Rival this week...

What i did to start with was set the limit screws first then adjusted the cable tension to make up and down shifting smooth,but i was not getting success in every gear at the rear,sometimes the front was refusing to shift or over shifting depending on what rear gear I was in,spent ages trying to sort it...

But then i put booth limit screws in the half way position and sorted the cable tension first then when that was smooth in all gears,then i set the limit screws to make sure of no over/under shift...All now sorted..

RichR2

The only thing that I can pinpoint is it tends to happen more frequently when the chain is in the middle cogs of the cassette, but then again, thats probably when you are most likely going to be shifting rings at the front anyway. It's got me stumped.

bruce225

That's when my problems started,Large front small back no problem shifting,small front large back no problems shifting with limit screws stopping any drop offs,but when I was in middle cogs the shifting would go all out of sync at the front.

But i noticed the limit screws looked to be at there extremes that why I centered them and sorted cable tension out first then set screws.

But sounds like you may have tried all this first,but worth giving it a go set every thing in the middle then readjust rather than minor adjustments of what your set up is now....

JohnnyAllez

You want to be setting the H and L screws before tensioning the cable, leave some slack in the cable and set the low screw with no cable tension holding it, then pull the cable tight manually from under the downtube to see how far the top limit screw is allowing the mech to go and adjust that to suit, then tension the cable.

Check the angle of your front mech in relation to the chain-rings as well.

RichR2

I've tried very small changes to the angle of the mech in relation to the chain ring (whether it was parallel or not) but as its not the braze on type, I can't adjust it in relation to how the curve matches the curve of the chain ring.

One thing I have not tried is to reduce the gap between the teeth and the cage (along the curve of the chain ring), although its at 1mm already so I can only get closer by a fraction of a mm anyway.

onbike 1939

If the gap is already at 1mm then it's within limits so leave it alone. Is the big ring true without any kinks? Have you looked down from above as you turn the cranks? It may be worth lubing the pivot points on the FD as it may be that the FD is not moving through its complete arc with every change due to being impeded with winter gunge. Only when you're satisfied that the FD is moving freely should you move on to setting the High limit.

bruce225

JohnnyAllez wrote:

You want to be setting the H and L screws before tensioning the cable, .

Problem is when newbies and I include my self in this bracket,if you get too carried away with the limits screws before sorting cable tension you can end up loosing full motion of the mech, and no mater what cable tension you do it won't change smoothly...

Not accusing you Rich of been a newbie..

ride_whenever

TBH just take it into a good lbs, they'll probably spot something you've missed.

Or give us loads of pictures of your mech position as I'd imagine theres something not set quite right.

RichR2

Thanks onbike 1939, big ring is true but you may have hit on a possible cause and something I've not tried. I'll give the FD pivot points a good lube and check moves freeley through its arc.

RichR2

Thanks ride_whenever, if I don't sort it myself then the 'good lbs' it will have to be.