Removing Rust
 

I just found a bit of rust on my front derailleur cage. Ultegra 9 speed Triple. Since I have everything shifting so good, I don't want to remove it and soak it. Would a bit of vinegar take it off and not attack the paint?

Sure, that should be fine. Clean it off afterward and spray it with a water displacer.

Any vinegar that stays on long enough to remove rust could harm some paints too. Vinegar should also be rinsed off pretty well as it can eat through chrome if left on long enough. Not a great risk but if it gets into some little crevice's and left there you'll find the damage later. Just hose it down with water afterwards.

I'd just wipe it off as best you can and maybe use a drop of some sort of oil on your rag to help discourage further rust. I wouldn't want to use an acid on it if you aren't going to take it off. You might get some on the chain and other parts that will have their finish messed up and then they'll start getting surface rust too.

But maybe not. It's sort of a toss up.

Spray some ACF-50 and be done with it.

Naval jelly will remove the rust. Clean it off completely afterward and put some oil or grease on the affected area to inhibit the rust returning.

0000 steel wool. Just did this

Coca Cola.

If it's just surface rust a bit of WD-40 and a green scouring pad will take care of it in a jiffy.