Adjusting front mechs
- Thread starter Alison
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Both much of a muchness Tbh.
By highest gear, do you mean big chainring?
Make sure the limit screw is wound out so the mech cage can actually move out that far, the rest of it is controlled by the tension on the cable and the amount of cable being pulled by the shifter.
Some mech/shifter/chainset combinations work better than others.
And if the bottom bracket axle is too long for your particular chainset then it may put the big ring too far out for the front mech cage to ever reach it.
Now I think about it.... rear mechs DO seem much simpler!!
By highest gear, do you mean big chainring?
Make sure the limit screw is wound out so the mech cage can actually move out that far, the rest of it is controlled by the tension on the cable and the amount of cable being pulled by the shifter.
Some mech/shifter/chainset combinations work better than others.
And if the bottom bracket axle is too long for your particular chainset then it may put the big ring too far out for the front mech cage to ever reach it.
Now I think about it.... rear mechs DO seem much simpler!!
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not all front mechs match shifters either. different cable pull, different reach
Is it an issue on a new set up or has the big ring selection issue happened over time?
Often cable stretch over time will require an adjustment at the derailleur end rather than just playing with the adjusters. Hold the shift lever hard against its stop in the big ring position. As you release and let the lever find its own position watch and see if the fd cage moves back towards the middle ring
Often cable stretch over time will require an adjustment at the derailleur end rather than just playing with the adjusters. Hold the shift lever hard against its stop in the big ring position. As you release and let the lever find its own position watch and see if the fd cage moves back towards the middle ring
jonthefish
Senior Retro Guru
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I agree. Front mechs are a pain. As legrandefromage says, if it is a new set up then make sure that the shifter is compatible.
The Parktool site has a good 'how to'. http://www.parktool.com/blog/repair-hel ... -section-5
The tip on Parktool about test shifting by pulling the cable rather than using the shifter is a good one - that will let you test that the mech and limit screws have the capacity to cover all three rings.
If it is a new set-up the height that the mech is mounted on the frame tube might also be an issue. I had to set the mech considerably higher than normally recommended to get the chain lifted onto the big ring on a recent build with Middleburn rings.
The Parktool site has a good 'how to'. http://www.parktool.com/blog/repair-hel ... -section-5
The tip on Parktool about test shifting by pulling the cable rather than using the shifter is a good one - that will let you test that the mech and limit screws have the capacity to cover all three rings.
If it is a new set-up the height that the mech is mounted on the frame tube might also be an issue. I had to set the mech considerably higher than normally recommended to get the chain lifted onto the big ring on a recent build with Middleburn rings.
Just did an 'out of the box' new setup with Deore. It was amazingly faffy, whereas the rear needed nothing more than a half twist of an adjuster to get it perfect (after the limit stops had been done).
It's a spiral of complication, after the daft idea (needlessly?) to index the front. I got it right in the end but it would have been simpler to have fitted a thumbie!
It's a spiral of complication, after the daft idea (needlessly?) to index the front. I got it right in the end but it would have been simpler to have fitted a thumbie!
They take longer, not particularly harder though. Many more things to get wrong. At least with a rear mech you screw into the frame, with a front you've got to get the height and the orientation right before you can even start on stop screws and cables.......Alison":21kf64sr said:
I've never understood the struggle some have with front mechs.... Once I get one with the right size band, it's all but done.
Set it on the seat tube, gently snug the clamp bolt. Manually move the mech thru its arc, ensure it clears all rings by at least 1mm, not more than 3mm. Make outter sideplate parallel to rings. Tighten.
Set shifter in low gear, set low stop on mech approximately so outside of cage is parallel to middle ring. Turn out shifter barrel by 2 or 3 turns to give some adjustability. String the cable, pulling it gently taught.
Adjust the hi stop to allow it to shift to the big ring. With top gear selected (big ring, little cog), the outer cage should just clear the chain (0.5mm-ish). Adjust Hi stop screw to suit. Center chain on cogs (middle gear), and drop to middle ring. Should drop easily. If not, adjust barrel adjuster in until it does.
Drop down to the granny. If chain overshoots, adjust Lo stop as required (screw in slightly). If chain doesn't drop easily, screw the Lo stop out slightly. It can be a fine compromise between quick shifts and overshifts.
Now shift from granny to middle. It should go easily, requiring at most a slight "push past" on the shifter. Rapidfires and Gripshift and indexed thumbies are built to allow this.
In short, align it, stops are only for big ring and little ring, barrel adjuster is for the middle ring.
J
Set it on the seat tube, gently snug the clamp bolt. Manually move the mech thru its arc, ensure it clears all rings by at least 1mm, not more than 3mm. Make outter sideplate parallel to rings. Tighten.
Set shifter in low gear, set low stop on mech approximately so outside of cage is parallel to middle ring. Turn out shifter barrel by 2 or 3 turns to give some adjustability. String the cable, pulling it gently taught.
Adjust the hi stop to allow it to shift to the big ring. With top gear selected (big ring, little cog), the outer cage should just clear the chain (0.5mm-ish). Adjust Hi stop screw to suit. Center chain on cogs (middle gear), and drop to middle ring. Should drop easily. If not, adjust barrel adjuster in until it does.
Drop down to the granny. If chain overshoots, adjust Lo stop as required (screw in slightly). If chain doesn't drop easily, screw the Lo stop out slightly. It can be a fine compromise between quick shifts and overshifts.
Now shift from granny to middle. It should go easily, requiring at most a slight "push past" on the shifter. Rapidfires and Gripshift and indexed thumbies are built to allow this.
In short, align it, stops are only for big ring and little ring, barrel adjuster is for the middle ring.
J
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Never understood the struggle either, two minutes tops from picking up the mech* - maybe we should run classes... 
*excluding time spent being a dipstick with oval chainrings!
*excluding time spent being a dipstick with oval chainrings!
