Hi all

I tried to do a bit of DIY when my gears were making a grating noise on the large chainring, but I've messed up my front derailleur cable and am struggling to get it back on. I've managed to adjust the L limit screw and everything runs smoothly with small front chainring, but it doesn't seem to want to go onto the large chainring. Also the H limit screw doesn't appear to do much when I turn it to its extremes?

Any pointers?

Thanks, Paul

You need to adjust the cable tension , which can be done at the shiftier or somewhere on the frame. to adjust just back off the adjustment barrel 1/8 a turn until the chain move onto the next gear. it best to adjust the H & L screws when the cable not connected to the derailleur (s).

Use the instructions for setting up and adjusting derailleurs found at www.parktool.com. Do all of the steps in sequence leaving nothing out.

Let's back up the truck and just assume this is a new front derailleur (FD) install and adjustment.

1. Inspect the FD and the clamp or fixing bolts.
a) looking from the side of the bike, is the FD cage able to clear the big chain ring when it pivots out? (Maybe test with your gloved hand by flexing it - watch for frayed derailleur cable - pokes painfully into fingers). About 2 - 3 mm is a good starting point for bottom of outer cage above big chain ring.
b) looking from behind the rear derailleur toward the front along the chainline, is the outside of the cage parallel to the plain of the main triangle? Some cages aren't flat. They have a skip at the bottom section, making it wider. Then I align with the upper section of the outer part of the FD cage. My experience tells me that most FD outer cages should be just barely toed in about 3 or 4 degrees both inside and outside parts of the cage and that's because the FD cage should be trapezoidal as viewed by the chainline.
c) snug down the fixing bolts on the FD clamp to the seat tube so it doesn't move.

2. Inspect joints and lube FD
a) get some of your favourite spray lube with straw, preferrably for bikes and slightly heavier than WD40, and just a little tiny drop or shot into joints, over springs.
b) pivot with gloved hand again and work it in.

3. Inspect/Install FD cable.
a) pre-thread the cable - if this is an old cable and frayed where it was clamped before, I would use a new one.
b) now note where cable makes contact with housing, shifter (on handlebars), under the bottom bracket, etc.
c) slide cable back out, take dab of heavy grease (salt, corrosion, waterproof - I prefer Phil Wood grease) and between finger and thumb - coat the cable
d) run cable back in through housing, cable routing in frame, and into FD cable clamp, and then just finger tighten lightly the fixing bolt. If you aren't sure how cable is clamped back in, think about the routing of the FD cable and what would give a fairly good alignment so the shift lever tension will cause the FD body to pivot. There should be a small screw with 4 - 5 mm allen hole that bolts a grooved plate about 1cm. The cable should fit in that small groove and align with the general direction of pull.
e) make sure FD shifter is set to smallest chainring and at most relaxed position, and any cable tension adjusters are screwed mostly in (so you have shortest cable travel), get a 4th hand tool (a special pair of grip/pull pliers that grab the end of the cable then stretch it) or you can use some lineman pliers or even your hands if you have strong fingers. Pull firmly, but not enough to pivot the FD, and then snug down the cable bolt.

4. Limit adjustment
a) shift to large cog on rear, and small chainring front, then set low limit by screwing it in and watching FD cage move out, then back out to align with chainline plus some clearance. If cable is too tight, twist adjustment barrel down to give a bit of slack so FD cage reach limit and is resting against limit screw.
b) shift to small cog rear, try to shift to big ring front. Loosen high limit screw until it gets on big ring. Line with chain, plus provide sufficient clearance so chain doesn't rub against chain.
c) shift back and forth big to small chain ring and make any final adjustments.
d) note that cables may stretch a little in the first few hours/days and then settle on a fixed position. If you want to take up that slack, do so at the barrels on the shifters (if you have them).

Unless you ding the FD, crash, knock the alignment out of whack, etc., the limit screws shouldn't need tweaking very often or ever.

Thanks guys, very detailed reply gyozadude, appreciate it. Will give it a go and let you know.



Paul

Finally tackled it! Works perfectly now Thanks again!

A Happy Paul

DIY FTW : )

(some lower case so my acronyms aren't de-capsed, dammit)