Front shifting issues help

[ishaw]

I don't normally have issues setting up gears, but I've hit an issue I can't some.

Building a bike to sell from parts in the stash. Frame is a steel trek 9 series, shifters are SRAM 7.0 as is rear mech, front is a Shimano.

Everything seems aligned, shift from granny to middle is fine, but it doesn't want to shift to big ring. The mech seems to end up in the right place, over the big ring, it's just not picking up the chain along the way.

Cranks are FSA power pro, Bb is a 113 which research suggests is correct, and as the mech ends up over the big ring, seems to be right.

I just can't work out why the chain isn't being moved along with it.

Any ideas why?

 

[nicklej]

You could try loosening the high limit a smidge and increasing tension by the barrrel adjuster a small amount and then checking if that works. Going into the big ring always takes the most tension so I reckon if you're getting the click then the high limit is turned in just a smidge more than it should be.

 

[ishaw]

Thanks, though the tension is as high as I can get it and I don't think it's a limit screw issue, but I'll check.

 

[novocaine]

out of parallel cage? doesn't have to be out by much to screw things up.
other thing is to check the rear ramp of the cage isn't fubar.

then it's a setting issue, or a cable pull issue, we all know how much Shimano enjoy messing about with ratios there.

 

[FluffyChicken]

grab some pictures (just because I like picture).

First is always the limit screw, slacken it off way too far.
It should over-shift a bit and then move back on the click.
Saying that I don't know SRAM shifter that well.

Are there no pins/ramps on the top ring?

Which Shimano model front mech, it shouldn't matter but it gives something to go with.

113 shouldn't be a problem as it's either at 47.5 or at the 50mm chainline position.
Chainring isn't too far from the chainstay.
Rear mech not bent inwards ?

if the band is 28.6, try a wider mech with a shim (modern ones).

Pretty much all the things you'll already have checked though since your certainly not new to this.


Could just be, ah bollocks, find something else.

 

[RetroDavy]

If 1) the profile of the front mech cage is a good match for the chainrings (number of rings and for the ring sizes), and 2) the bottom of cage is clearing the top of the big ring just enough, then 3) I'd look at the cage sides being parallel to the rings - a small rotation out of line can mess things up, as Novocaine suggested. No. 3 caused my most recent headache.

 

[ishaw]

Thanks for the advice, I'm time poor right now but will try the various suggestions.

The front mech is I think an acera low mount affair. Never been a fan, much prefer the more retro style top band, top swing.

In my defence, I've not played around with the angle of it, it seems to be pretty straight as I've fitted it. Not checked for cage wear but it's pretty clean and tidy. Might swap it for something more traditional.

 

[minor_LEGEND]

Try raising the mech a bit, height can make a difference.

When clamping the cable at the pinch bolt, check the cable is routed as Shimano intended, follow any markings in the clamp area, lastly wind the low stop screw in a tad, clamp the cable with minimal (no slack) then let the stop screw back out to ensure there really is 'NO SLACK'.

 

[elite504]

Worn pivots. Almost for cert. Grab the cage and waggle it, see if you have an alarming amount of play.

 

[ishaw]

Sorted. I was a clown. Limit screws were the solution. Usually first port of call, for some reason I overlooked them.