I hope one of you experienced wrenches can help me out. I built up my first bike recently (except for the headset) and for the most part it seems to work OK. However my front derailleur isn’t quite dialed in. When I am in the big ring it rubs the inside guide edge (of der) when in a bigger cog. If I click my sti shifter a touch it (front der) jumps to the left just a hair and all is well. I am not sure why I seem to have 2.5 positions in my front der (this is nine speed ultegra double).
Is my problem the front der adjustment or shifter or something else. I am kinda lost but (ok I admit it) too embarrassed to take to the shop for something like this. Thanks!!
I’m a little confused by your description but I think your problem is either a hi/lo limit screw problem or a chainline problem. If it only happens in certain rear gears, its a chainline problem and there’s nothing you can do to avoid having to “trim” your derailleur except run a better chainline or maybe get a longer-chainstayed bike. If it happens in all the gears, its probably a limit screw problem. I haven’t messed with my road or tri bike f. der in a long time but I know shimano mtb derailleurs label their high and low limit screws with a “h” and an “l.” Just turn the appropriate screw until the derraileur moves far enough that the chain passes through without touching.
It is not uncommon for the chain to begin rubbing on the front der. when you shift up to the larger cogs in the rear while still in the large ring in the front - it is just a matter of chain line. The same thing most likely occurs if you are in the small ring in the front and shift towards the smallest cogs in the rear. The Ultegra has a ‘feather’ position on the front shifter to place the der. between the large and small chainrings to allow for these chain line situations. You are lucky that you can click down to the feather position from your big ring. I can usually only get to that position from my little ring but when clicking down I can’t seem to find the right pressure for the half click.
If the der. was wide enough to allow for a wider range of chain lines then it would not shift as crisply because it would have to move further before it pushed the chain hard enough for a shift. The half click is in the shifter, not in the der. My buddy has a cyclocross bike that I ride sometimes that has an old narrow der. (dura-ace circa 1990 or something) but he put new Shimano Sora shifter/brake levers on it. The Sora does not have the feather position (since it is a less expensive model) and so the chain rubs without the ability to feather.
A little chain rub won’t kill you, it just tells you how crossed up your chain line is.
Your derailleur is working fine. You should have two positions when on your large chainring (this is how you avoid rubbing on the inner-side of your derailleur while in a lower gear). You just need to dial in the tension of your derailleur cable (it’s probably a little too tight).