Front derailleur frustrations

[moonlite]

I find most bike-building / fettling tasks enjoyable and satisfying -- except for installing/setting up front derailleurs. The technique just seems to elude me.

Take today: I installed a new (to me) Middleburn RS7 Triple on my 1999 Kona Explosif. I checked that the bottom bracket spindle length was right and it was (the existing one is the correct length) and adjusted the height of the derailleur cage so it was c 2mm above the big ring. But after I connected the cable, I couldn't get the chain to change up onto the big ring.

Tightening the cable got it nearly there, but not quite. I adjusted the upper limit screw as far as it would go, and the chain reluctantly made its way onto the big ring, but only with huge effort at the lever. Reducing the tension started the whole issue all over again -- it's happy in the middle ring, but can't quite make it onto the big one.

It's not the first time I've had this issue. In fact, this is usually the way it goes with the front derailleur when I have a go at it. What am I doing wrong?

 

[Guinessisgoodforyou]

Is the cable on the right side of the pinch bolt on the mech? Sorry, not teaching grandma to suck eggs

 

[moonlite]

Is the cable on the right side of the pinch bolt on the mech? Sorry, not teaching grandma to suck eggs

Well, since you ask . . . I don't know! I'll check.

 

[legrandefromage]

What mech and shifter?

And I usually fit the cranks to suit the frame, ignoring any quoted axle length, just as long as the rings don't hit the frame

 

[moonlite]

What mech and shifter?

And I usually fit the cranks to suit the frame, ignoring any quoted axle length, just as long as the rings don't hit the frame

It's LX M-570, both shifter and derailleur. Top-pull, if that makes a difference.

Looking at it, it does look like the spindle could go a mm or more shorter . . . Sheldon Brown rather interestingly cites 110-113mm for this chainset which is quite a big variation. 2mm would make all the difference to the shifting. Tempted to order a new one.

 

[Mod-Master]

If at first you don’t succeed, try and try again.

If there are no compatiblity issues, then persistence is key

 

[mk one]

You can pull the mech out by hand, if the screw is not stopping it and it is not reaching then there is nothing you can do apart from move the crank inboard.

 

[Mod-Master]

I usually have a plastic lever I lodge between the ring and the cage to hold it in the furthest position, I tighten the limit screw then take up the cable slack, I repeat on each position making sure that on every shift the cage is in line with each chainring using the barrel adjuster and occasionally undoing the pinch bolt.

Then I install the chain and check again. Then, after much pain and struggle it’s shifting fine

However on some bikes, the front mech just refuses to shift up to the larger chainring, like on my super v, where I literally set it up every week, just wouldn’t do it. I even changed it, and still wouldn’t accept shifting. And that’s how it came stock.

 

[Woz]

Middleburn RS7 can be as low as 107mm, but more typically 113mm if it helps.

110mm is typically not symmetric. There used to be a 110.5mm which was symmetric, but hard to find.

 

[moonlite]

Lots of good advice here -- thanks everyone.

I have one of those red plastic thingies that new front mechs come with which I will dig out for further fettling.

And yes, the current spindle is 113mm, but I think I can get my hand s on a 110.5mm locally which I think is what's probably needed. (But what is meant by symmetric when it comes to spindle length?)