todd92371

Hola,
Have a question... Running a Sora FD-R3000 on the front and rear of my gravel bike. 9 speed on the back and 2 rings up front. I'm noticing that the front der. cage is dragging on the guards when shifting high and low in the rear. I'm having to do small clicks constantly in the front to compensate after shifting high and low in the rear. Is this normal? Or should one shift in the front allow gear changing through the whole cassette without rubbing the guards?

Thanks! todd

Andrew R Stewart 

MtB front drivetrain systems are pretty much all designed with a single ft der position after shifting, the cage contours and ring C-C spacing try to eliminate chain rubs as one shifts across the rear cog set.

Road systems can have shifters with a trim feature, specifically to eliminate rubs. It is generally agreed that front trim features make for a better working system and are found on the higher grade groups more than on the entry level ones.

When you use the term "guards" do you mean the sides of the ft cage? Or are their chain guards attached to the rings on their outer and inner sides that the chain rubs on? Big difference as to what is happening and what might be done to correct the rub. Andy

todd92371

Thanks so much!!!! Yeah, it's the sides of the ft cage.. As I shift in the back... the chain will rub on the sides and I have to counter shift the front a bit to compensate.

ClydeClydeson

This is normal and you are using the 'trim' clicks in the shifter properly. If the trim clicks do not eliminate rubbing when on one extreme or the other of the cassette then you would fix it by adjusting the cable tension on the front derailleur.

Rolla

You might also check the front derailleur straightness and height, relative to the chainrings.

79pmooney

For a little background and history - shifting used to be done with simple levers; no indexing. To shift both derailleurs, you moved the lever past the new cog or chainring, then brought it back. With the rear derailleur, it was simple. You brought the derailleur back to in line with the cog and you heard the chain run silent. What gear you were in in front didn't matter. (Well, on the older vertical parallelogram derailleurs, the amount of chain taken up in front changed how the derailleur behaved so the feel was different between large chainring and small but where you needed to locate the rear derailleur after the shift didn't change.)

Now, with front derailleurs it was and is a different game. Yes, the same overshift (a lot back in the day before ramps, pins and funny shaped teeth on chainrings, now almost nothing). But where you need to move the front derailleur cage to after the shift is entirely dependent on the cog being used in back, especially when you are on the smaller chainring(s).

It sounds like you are getting the hang of how much you need to tweak the front derailleur after a shift. Good work! Now the penalty for not getting it right isn't very big. Noise. (Can your brain stand it? It's not affecting anything else.) Front derailleur cage wear. Virtually all cages have hard chrome finishes. It takes quite a while to wear through it and there is usually plenty of material to go after that. I did used to kill my front derailleurs regularly in about 5000 miles but that was when I was racing and going fast enough and breathing hard enough that I could not feel or hear the rub and my focus was so elsewhere I simply didn't care. SunTour derailleurs were cheap, especially as a bike shop employee where we sold Japanese bikes. Once a year a new one went on. Those were also very light derailleurs with thin and narrow cages.

A step in the learning curve for front derailleurs is that there are times when a touch of rub is good. In your lowest gear, small front to largest rear. If the inside of the cage just touches the chain, the chain cannot fall off. Likewise high gear, big chainring to smallest cog. Security. And when riding on an inner chainring and you want to use a small cog, the chain may hit the teeth or pins on the next larger chainring and try to climb up and shift. Slightly restraining the chain with the outer plate of the front derailleur can keep it off those pins and teeth, (Of course, that small-small combination is the verbotten "cross-chaining" for which you will be flogged to eternity in the next lifetime but some of us do it regularly on hard climbs when the road levels out for a minute rather than do a pair of double shifts. My next lifetime is going to be short and unpleasant.)

Welcome to the world of front derailleurs! In the bikeshops, we used to call them bumblebees. They shouldn't work/fly but they do.

cyccommute 

What you are experiencing is somewhat normal but it might be exacerbated if your cable isn’t tight. Shift to the lowest tension on the cable (low gear) and pluck the cable. If the cable is loose, you should use the adjusters to take up the slack. This will hold the derailer in proper position and make trimming less necessary.

If the cable isn’t slack, you may just have to live with it.

Andrew R Stewart 

I'll add some backround to this need to trim the ft der cage to eliminate rub after shifting.

Back in the day this trimming was done by one's hands, the shift lever would be nudged one way or the other to position the cage centrally WRT the chain. And we called it "trimming" When indexed systems came onto the market the shifters were still using a friction function for the ft der. So ft trimming was still a manual function. With the advent of STI (brifters) the ft trimming was built into the shifter, still needing a manual step but the amount of corrective trim was programed by the shifter internals. To offer STI controls at lower price points (Remember Shimano is famous for their market plan of introducing their newest features at the upper groups first) they eliminated some of the shifter's complexity. So some of all the trim features went missing. Shimano has learned better that trim features is a wanted thing at nearly all price points and has trickled down this feature to lower cost groups as time goes on.

Interestingly is that early on in the MtB indexing systems Shimano provided a small instructional sheet (pictural in it's layout) describing the cog and ring combos that might have some rub. Very few people ever saw this slip of paper that came with the new bike's paperwork. I have never liked the industry preference to not provide operational instructions for their products, this is on both the manufactures and the LBS people. Many shops would toss all but the owner's manual when assembling the bike. Rant over. Andy

todd92371

Thanks!!!!!!