Mountain Biking - Chain rubs front derailleur, how can I adjust it?

I don't know much about bikes but when I have the front derailleur set on the highest gear the chain rubs against it and on long rides it gets irritating. Their are 2 screws on the top of it to adjust it I believe and I wanna know if it's possible to adjust it so that the chain isn't constantly rubbing it.
Will adjusting it so the chain doesn't rub mess up changing gears?
It rubs on the side that's closest to my leg

If its a brand new bike, I suggest taking it back to where you bought it and have them adjust it. It's a very time consuming job and very frustrating at times. If you want to do it yourself, a good guide is the Barnett's Manual and the installation sheet that came with your front derailleur (if you got one).

From what I've experienced, rub can be encountered by any of these factors:

1. Wrong chain size (8-speed chain in a 9-speed derailleur, that's what I have)
2. Derailleur clamp set too low or too high on seat tube
3. Wrong cable tension
4. Wrong derailleur angle
5. Wrong gear combination
6. Wrong limit screw setting

Originally posted by Chi
If its a brand new bike, I suggest taking it back to where you bought it and have them adjust it. It's a very time consuming job and very frustrating at times. If you want to do it yourself, a good guide is the Barnett's Manual and the installation sheet that came with your front derailleur (if you got one).

From what I've experienced, rub can be encountered by any of these factors:

1. Wrong chain size (8-speed chain in a 9-speed derailleur, that's what I have)
2. Derailleur clamp set too low or too high on seat tube
3. Wrong cable tension
4. Wrong derailleur angle
5. Wrong gear combination
6. Wrong limit screw setting

Limit screw, is that the screw that i was talking about? The 2 screws at the top?

Yes.

http://cyclones-world.net/images/rub.jpg

Here is a picture of where it's rubbing. The screws say High and Low. Which one would I want to adjust?

//edit Oops, hope nobody saw the picture of my car...Pasted wrong image url :P

Try loosening the H screw, or increasing cable tension.

What gear combination does it rub on?

All you need to know about front derailleurs (Adobe Acrobat):

http://www.bikeforums.net/barnettes/barnetts_ch33.pdf

Look at the troubleshooting tables starting on p. 19

That's what I'd use for this.

Originally posted by Chi
What gear combination does it rub on?

Exactly.....if your running it in 1 and 9 and it rubs, then its your fault. If if rubs through every combination, then take it in to get adjusted.


On a 27 speed drive train you should not be running cross gears too often. (eg: large front chain ring large rear cog; small front chain ring small rear cog.) This will result in rubbing on the front derailleur and stress on the chain. Too much rubbing can be from misusing gear combinations. Instead, shift often and run your chain straight.

To be honest I'm not sure what it rubs on now. I usually ride 3 on the front 5 or 6 on the rear since I'm on a paved trail and can go for miles like that non-stop and it rubs. My crank arm is messed up (See my other thread) and I wont have a replacement until around next Tuesday so I can't really go out and test it now. I'll remember to pay attention to it more the next time I go out and try all the other gears to see what it does.

Since your bike is new, chances are your cable has stretched. This is normal. There is a barrel adjuster (screw thingmabobber) at the shifter (gear changerthingy) turn it out about 1/2 turn. That'll lengthen the housing thus shortening the cable.

If this continues, unscrew the H limit screw by like 1/4 turn!

L8R

I had to adjust mine today but I had to lower the derailleur by a smidge and readjust the screws but works great now. Mostly trial and error on my part but after about 1/2 hour I got it to shift and not rub!

If you adjust the limit screw you will probably solve the prob but don't turn it too far or the chain might shift right off.

i run mine on 2 in the front 8 in the back and i have this problem. should i too adjust the "H" screw aswell?

If it's an 8-speed, 2/8 is an extreme combo. It doesn't work for me either. Usually, you don't want to shift past 6 or 7 on the rear if you're in the middle chainring.

well thats dumb:crash:

If your chain is rubbing the derailleur while in the middle chainring (up front), then your derailleur ISN't centered. You should get NO chain rub in any of the gears while in the middle chainring, especially if using an 8 speed system. If you do, use the barrel adjuster to slacken/tension the cable as necessary.

What I do, is adjust my rear derailleur with the chain in the middle ring up front. Once the rear is dialed, I fine tune the front. One of my double-checks is to go through the rear with it in the middle ring and fine tune cable tension so there is no rubbing (or very, very slight while at outside ranges).

L8R

barrel adjuster? (newb here sorta lol)

The screw-ey-ma-thingy-jobber on the shifter. Where the cable enters the shifter, there is a plastic knob. It might be covered with a rubber boot. Slide the boot out of the way and you'll see it. Turning it out (counter clock wise) will tighten the cable tension.

L8R

I have to take my bike to the shop today to get a new crank arm put on so I'll get the guy to check it out for me while I'm there.