eminefes

begin rant/

I was recently having problems with my chain rubbing on the FD when I was in the largest chainring and smallest cog. Turning the H limit screw didn't help, so I concluded that I needed to increase the cable tension on the FD, but I had no barrel adjuster.

Anyways, I took my new bike to my LBS and had them install barrel adjusters and tune the FD. When I get the bike back I notice that the chain still rubs some when I'm in the big ring and small cog, so I turn the barrel adjuster to increase the tension, and voila, the rub goes away.

But then I end up having problems with the chain falling off the big ring and into my cranks when I'm in the 6th cog and shifting from the small ring to the big ring, so I decrease the tension on the FD and the problem goes away. Now I'm just confused.

It turns out the FD's height was set too high, so I lowered it to the point where a penny can just fit between the big ring and the derailleur cage. Now I have the tension increased without the chain falling off.

Thing is, you'd think my LBS would have noticed that problem when they "tuned" the FD. *sigh*

/end rant

andr0id

FD adjusting is very subtle and lots of people just don't get it. You've discovered the first key point which is 1mm - 2mm gap between the cage and the teeth. A penny is 1.45mm and is about perfect. A nickel is 2mm. No more than a nickel.

The next point is aligning the outer cage exactly parallel with the chain ring for Shimano or for Campy you align the inner cage with the chain ring.

You're on your way to being an ace mechanic.

gascostalot

I hate adjusting the damn FD, especially on indexed shifter. I mean it's such a simple concept but it's the world hardest thing to get right.

Panthers007

Agreed. Properly adjusting the FD may seem straightforward, but as you've seen it's anything but. Most people never get it right - including the LBS's local 'wrench.' Keep riding & learning!

Velo Dog

Indexed front never made any sense to me anyway. Its like indexing a light switch.

deraltekluge

I thought light switches are "indexed".

Panthers007

In France, light switches are timed. When you're about halfway up the stairs to your destination, they turn off. I was quite worried about taking an elevator...

Shimano now encloses a rather confusing chart with their front-derailleurs. It shows which gears one is likely to encounter rubbing/noise from - in a properly adjusted FD.

Here you go:

gascostalot

I actually like friction shifters on the FD. What? You hear noise? Adjust the shifter and make the noise disappear...

frankenmike 

+1 The micro-indexing front gripshifts also allow you to trim.

Nermal

That's definately an interesting thought.

Kimmitt 

I'm also a big fan of friction shifters on FD's. 3-speed IGH's too, actually.