Chain Rubbing Front Derailleur

[CYCLONE]

I adjusted my derailleur like so
0) Disconnect cable...
1) Put chain on smallest chain-ring and largest cog... Lowest gear
2) Adust the LOW STOP on the front D until the inside plate touches the chain... Then back off until it just clears.
3) Make sure front left shifter is in lowest position (STI press little lever multiple times to make sure
4) Pull out all of the slack from the cable that you can, place it into the binder of the front D and tighten the cable binder bolt (be sure you place the cable through the binder the correct way!

Now the cable should be tight and the bottom adjustment should be right. Now to check the top adjustment...

1) Shift rear to smallest cog.
2) Try to shift into front biggest chain ring.
3) adjust HIGH adjustment until it touches chain on the outside of the front D shift plate. Then back off until it does not touch.

If you try and cannot get the thing to shift into the big ring then look to see when you press the shift lever does the front D hit the HIGH adjustment stop... if so LOOSEN the HIGH stop until you can... then go back to #3.

That worked great but my chain still rubs. I could go back and adjust it so the derailleur is even closer to the chain.
Do you think that would lessen the rubbing ?

[Surly LHT]

What I have always done put my chain on the big ring on front and the small cassette on rear then pull the cable slack out. You may need to back off on the cable adjustment a little or put a little pull on it just make it clear the chain when you are on the big ring on FD and it should work fine for the smaller chain ring on the FD when you are on the smaller chain ring you should be able to go threw all the gears on back RD with out it touching your FD. If not you still need to do a little more adjusting. To your cable of the adjustment screws. Hope this helps you out a little.

[erdem]

there is a detailed tutorial about front derailleur adjustment in park tool's web site. have a look especially adjusting h-screw part. when adjusting h screw i pulled the cable with my hand.

http://www.parktool.com/repair/readhowto.asp?id=75

and i need to readjust front derailleur's height. the gap between the teeth of the outer chainring and lower edge of the outer cage plate should be 1-2mm. make sure that cable tension is relatively low when making this adjustment else you may scratch out your frame. when making height alignment i pulled the inner wire cable by hand. when you increase cable tension by hand derailleur moves above the outer chainring so that you may see the gap more precisely. i also checked fd's angle.

some people suggest adjusting rear derailleur before front derailleur because front deraileur adjustments are affected by the position of the rear deraileur.

[CYCLONE]

(08-09-2010, 04:46 AM)erdem Wrote:  there is a detailed tutorial about front derailleur adjustment in park tool's web site. have a look especially adjusting h-screw part. when adjusting h screw i pulled the cable with my hand.

http://www.parktool.com/repair/readhowto.asp?id=75

and i need to readjust front derailleur's height. the gap between the teeth of the outer chainring and lower edge of the outer cage plate should be 1-2mm. make sure that cable tension is relatively low when making this adjustment else you may scratch out your frame. when making height alignment i pulled the inner wire cable by hand. when you increase cable tension by hand derailleur moves above the outer chainring so that you may see the gap more precisely. i also checked fd's angle.

some people suggest adjusting rear derailleur before front derailleur because front deraileur adjustments are affected by the position of the rear deraileur.

My REAR derailleur looked fine so I just moved right to the front derailleur. I read how to check the height and angle of the front derailleur. Height and angle was fine so I didn't move it. I also adjusting my tension by unscrewing the clamp bolt and loosened it enough so it so it wasn't taut as heck in any 1 position. You said you pull the cable while you adjust the H screw ?

[erdem]

(08-09-2010, 09:34 AM)CYCLONE Wrote:  My REAR derailleur looked fine so I just moved right to the front derailleur. I read how to check the height and angle of the front derailleur. Height and angle was fine so I didn't move it. I also adjusting my tension by unscrewing the clamp bolt and loosened it enough so it so it wasn't taut as heck in any 1 position. You said you pull the cable while you adjust the H screw ?

i suggest checking rear derailleur's adjustments. they are so easy. but if they look fine you don't need to check. and also if front derailleur's height and angle adjustments seem fine don't bother.

yes exactly. there was already enough tension in the inner wire. than i maintained full pressure on inner wire by hand. while in this position i checked the gap between chain and outer cage plate. only there should be a small gap visible about 1 mm.

- if chain is rubbing cage, loosen H screw anti clockwise 1/8 turn, maintain pull pressure and check again.
- if there is a lot of gap, than tighten H screw until the gap is about 1mm.

and make sure chain is in outermost sprocket in rear and outermost front chainring when making these adjustments. for L screw vice versa..

and when making front derailleur's height adjustment there was little tension in the inner wire. i pulled the inner wire by hand to see the gap between the teeth of the outer chainring and lower edge of the outer cage plate. height and angle adjustments seemed complicated at first glance. but i finally made them and there is now a gap about a thickness of penny between the teeth of the outer chainring and lower edge of the outer cage plate.

are you sure which one is L and the other is H screw. if not sure you may select one screw. turn clockwise one full turn and then counter-clockwise. if you feel a lateral motion in the derailleur's body this is L screw else it is H screw. you should relax the cable tension completely using the cable barrel adjuster to make this test.

[CYCLONE]

Yes I already checked which screw is H and L .
Okay I did this , this time. For the L screw
Shifted to inner most rear cog and innermost CR
Checked cable tension was fairly loose and it was
Set gap 1/16 " between inner plate and inner chain when clearance was tightest when rotating cr
Tested by pulling cable ( not shifter) to shift derailleur to middle CR. It shifted there fine but if I pulled the cable farther(harder) it would go up to the biggest chain ring. (I guess that's normal) . There was no clicking when pulling the cable by hand . I guess that's normal too. It shifted back to the inner CR without over shooting it.
For the H screw
Shifted to outer cog and outer CR
pulled cable to ensure derailleur was against H screw
Maintained that pressure while checking gap at tightest point in CR rotation
Turned so the chain was 1/8 from outer plate.
Shifted to middle CR and back to largest CR using hand pressure on cable.
If shifting was slow (takes more than 1 revolution) loosened H screw and repeat. If it shifted past CR to outside tightened H screw and shifted again.
Finally
I shifted chain to middle CR and inermost rear cog
checked gap was as small as possible without rubbing , to reduce the gap increase cable tension using the barel adjuster counter clockwise, which the gap was close maybe a little less than 1/8 of an inch. I could have made it less but the cable tension seemed REALLY taut and I didn't want to tighten anymore
I then test shifted the front derailleuer through all thre CR's with every cog
the only time the chain rubbed the front derailleur was when it was in the small chain ring's three smallest cog and largest cog combinations . In other words in 4 combinations .
Thats not bad but it still rubs
The instructions I was going by said if derailleur rubs in largest CR check limit screw and cable tension but I skipped that cuz it didn't rub in the largest CR and if chain was slow to shift to smallest CR check L screw and cable tension which maybe too high. It was not slow to switch to smallest CR but they didn't say what to do if it still rubs in small CR .
I guess I'll double check the rear derailleur and do that whole thing again for the front again. I wonder what I should do differently in the process this time ?

[erdem]

(08-09-2010, 04:11 PM)CYCLONE Wrote:  Yes I already checked which screw is H and L .
Okay I did this , this time. For the L screw
Shifted to inner most rear cog and innermost CR
Checked cable tension was fairly loose and it was
Set gap 1/16 " between inner plate and inner chain when clearance was tightest when rotating cr
Tested by pulling cable ( not shifter) to shift derailleur to middle CR. It shifted there fine but if I pulled the cable farther(harder) it would go up to the biggest chain ring. (I guess that's normal) . There was no clicking when pulling the cable by hand . I guess that's normal too. It shifted back to the inner CR without over shooting it.

yes that is normal. if you pull the cable further it goes to the biggest chain ring. and also no clicking sound is normal because you pull the cable instead of shift lever.

when making L screw adjustments you check the shifting from middle chainring to smallest chainring. if shifting appears to be slow you turn L limit screw 1/8 turn increments anti-clockwise until shifting is adequate. the gap may be more than 1mm but should be still as small as possible and it should provide adequate shifting speed.

(08-09-2010, 04:11 PM)CYCLONE Wrote:  For the H screw
Shifted to outer cog and outer CR
pulled cable to ensure derailleur was against H screw
Maintained that pressure while checking gap at tightest point in CR rotation
Turned so the chain was 1/8 from outer plate.
Shifted to middle CR and back to largest CR using hand pressure on cable.
If shifting was slow (takes more than 1 revolution) loosened H screw and repeat. If it shifted past CR to outside tightened H screw and shifted again.

i also made it like this

(08-09-2010, 04:11 PM)CYCLONE Wrote:  Finally I shifted chain to middle CR and inermost rear cog
checked gap was as small as possible without rubbing , to reduce the gap increase cable tension using the barel adjuster counter clockwise, which the gap was close maybe a little less than 1/8 of an inch. I could have made it less but the cable tension seemed REALLY taut and I didn't want to tighten anymore

i haven't adjusted index settings yet i think your bike is a 3 chainring bike.

(08-09-2010, 04:11 PM)CYCLONE Wrote:  I then test shifted the front derailleuer through all thre CR's with every cog
the only time the chain rubbed the front derailleur was when it was in the small chain ring's three smallest cog and largest cog combinations . In other words in 4 combinations .
Thats not bad but it still rubs

in which gears? i think in some gear combinations rubbing is normal.

http://bikeride.com/gear-shifting

(08-09-2010, 04:11 PM)CYCLONE Wrote:  The instructions I was going by said if derailleur rubs in largest CR check limit screw and cable tension but I skipped that cuz it didn't rub in the largest CR and if chain was slow to shift to smallest CR check L screw and cable tension which maybe too high. It was not slow to switch to smallest CR but they didn't say what to do if it still rubs in small CR .

yes you're right. they didn't say anything what to do when it still rubs in smallest chainring. i'll try to check it on the bike when i go home.

(08-09-2010, 04:11 PM)CYCLONE Wrote:  I guess I'll double check the rear derailleur and do that whole thing again for the front again. I wonder what I should do differently in the process this time ?

nothing different. but i guess after making rear derailleur adjustment chain angle will change a bit. because when you tighten or loosen adjustment screw the RD's pulley position will change a bit laterally.

here is a nice document about rear derailleur adjustment:

http://www.bbinstitute.com/dl/dx_demo_chapter_32.pdf

after these adjustments if still there are problems, your rear derailleur may be bent. than you should take your bike to a LBS for professional help.

[CYCLONE]

Erem, you said it was normal for the derailleur to shift the chain past to the largest derailleur while pulling on cable enough. I could shift it past the largest CR to the outside. Is that normal ?

[CYCLONE]

From the parktool website. "After the H-screw is adjusted the inner wire should be re-tensioned to assure proper shifting".

How do you retension the wire and won't that mess up clearance ?

[CYCLONE]

It rubs in 4 places the smallest CR and 3 outer cogs(small) and smallest CR innermost cog (big). Yeah it is written in the books I read that cross gears will rub so I can accept the rubbing in the smallest CR and (outer) smallest rear cog and rubbing in the biggest CR and (inner) biggest rear cog . And even some in the middle CR and smallest (outer) rear cog and middle CR and biggest (inner)CR if I could get it to stop rubbing in the 2nd and 3rd rear cog with smallest CR. Because it's not expected to be rub-free in the cross gears. Thats normal.

[erdem]

nope. sorry i am not a native english speaker may be i might misunderstand you.

what i try to explain when the chain is in the inner chainring (smallest sprocket) if you pull the cable it shifts to middle chainring. and if you pull more it shifts to the outer chainring (biggest sprocket)

i think it shouldn't shift past the chainring to the outside. i tried it. when i pull the cable as far as in me lies it doesn't move past the biggest chainring to outside. or it doesn't try to shift outside. only derailleur cage rubs and a noise come from the chain.

if this is the case i think there might be some problem about h limit screw settings or it may not working properly. because the h limit screw should stop the outward motion of derailleur.

[erdem]

(08-10-2010, 03:43 PM)CYCLONE Wrote:  It rubs in 4 places the smallest CR and 3 outer cogs(small) and smallest CR innermost cog (big).

than may be you should check FD's height adjustment. loosen the cable tension a bit. then by pulling cable move derailleur. than inspect the gap between the bottom of the derailleur cage and the largest sprocket teeth.



but this is a bit tricky. before making height adjustment maybe only you should check the gap. than if the gap seems a lot you may adjust FD's height. if it seems reasonable than you don't need to do ..

[CYCLONE]

I did not notice english was not your first language. I tried messing with the H and L screw but it didn't do anything. I'm confident the height and angle of the derailleur are good. I could turn the derailleur inward a little bit so it would not rub when it's the lowest gear (small CR and Big rear cog) and add more tension to the derailleur cable to make the cage go out some more to clear the chain when it's on small CR and the 3rd and 2nd to smallest (outer) rear cog to keep from rubbing then. But I have the cable tension extra tight already.

[erdem]

yes i think when chain is a cross position i.e. smallest CR and smallest rear cog i think it may rub.

you mentioned your cable tension is extra tight and here is a quote from park tool's web site:

Quote:Although the limit screws will stop the derailleur, it is the inner wire and derailleur spring that make the derailleur move. If the inner wire has too much tension, the derailleur will not rest on the L-screw stop. If the inner wire tension were to change, the derailleur inner limit would also change, possibly causing the chain to fall off the rings.

this may be the case. but not sure !? actually i am not a bike mechanic and i made the fd's adjustment by the help of people in the forum. so i can't figure out what really happens off the cuff.

i am a total newbie at all i hope more experienced friends would help you about this problem..

[Bill]

Just wanted to insert this see if it helps... http://bikeride.com/gear-shifting/

[CYCLONE]

Cool ! I did not know that about the cable tension or that with a 21 speed there is only about 13 combinations people should use. I'll check to see if my cable tension is preventing the Front Derailleur from resting on the L screw.