front derailleur + idiot (me) = confusion

[Bob Ross]

I've got a Shimano Ultegra front derailleur & a compact 50/34 chainring, and whenever I'm in the big ring/small cog combination the outside of the chain is rubbing against the inside of the front derailleur cage.

I've been hesitant to do any tweaking myself, as A) I have no wrenching experience beyond washing & lubing; and B) Lennard Zinn's book is a bit oblique about addressing this specific topic. But then yesterday's mail brings me "Bicycling Magazine's Bike Tune-Up Guide", and right there on page 15 is what seems like a clear, concise explanation of how to fix my particular problem:

"Shift into the largest cog and smallest chainring combination. Look between the inside of the front derailleur cage and the chain. There should be 2mm of space. If not, turn the inner limit screw (usually the closest to the frame) until you get that 2mm of clearance. Next, shift to the smallest cog, biggest chainring combination. The outside of the cage should clear the chain by 2mm. Adjust the outer limit screw, if needed."

Ahem. Yeah, so, well, I try this and...nothing. Cage doesn't move at all. I try tighter, I try looser, nothing, nada, zip, zilch. No matter which way I turn the limit screw, the cage doesn't move at all. I figger maybe I'm turning the wrong screw, so I try the inner limit screw. Nope. (Plus -- separate problem, I guess -- now I can't get the inner limit screw back in!)

Help! Any ideas what I need to do to get the front derailleur cage to not rub against the outside of the chain when I'm in the big chainring/small cog combination?

Thanks.

 

[hd reynolds]

Help! Any ideas what I need to do to get the front derailleur cage to not rub against the outside of the chain when I'm in the big chainring/small cog combination?

Thanks.

1) Loosen the limit screw that stops your shift when shifting to the big ring.

2) Tighten barrel adjuster for the front der. until you see a gap.

3) Once you see the 2mm gap, tighten limit screw in no. 1 until it stops (dont use force to tighten, just gently tighten until you feel it stops rotating).

 

[geoinmillbrook]

I've got a Shimano Ultegra front derailleur & a compact 50/34 chainring, and whenever I'm in the big ring/small cog combination the outside of the chain is rubbing against the inside of the front derailleur cage.

I've been hesitant to do any tweaking myself, as A) I have no wrenching experience beyond washing & lubing; and B) Lennard Zinn's book is a bit oblique about addressing this specific topic. But then yesterday's mail brings me "Bicycling Magazine's Bike Tune-Up Guide", and right there on page 15 is what seems like a clear, concise explanation of how to fix my particular problem:

"Shift into the largest cog and smallest chainring combination. Look between the inside of the front derailleur cage and the chain. There should be 2mm of space. If not, turn the inner limit screw (usually the closest to the frame) until you get that 2mm of clearance. Next, shift to the smallest cog, biggest chainring combination. The outside of the cage should clear the chain by 2mm. Adjust the outer limit screw, if needed."

Ahem. Yeah, so, well, I try this and...nothing. Cage doesn't move at all. I try tighter, I try looser, nothing, nada, zip, zilch. No matter which way I turn the limit screw, the cage doesn't move at all. I figger maybe I'm turning the wrong screw, so I try the inner limit screw. Nope. (Plus -- separate problem, I guess -- now I can't get the inner limit screw back in!)

Help! Any ideas what I need to do to get the front derailleur cage to not rub against the outside of the chain when I'm in the big chainring/small cog combination?

Thanks.

http://bike.shimano.com/media/cycling/techdocs/en/bikecomponents/FD/SI-5JD0A_v1_m56577569830537825.pdf

Shimano has decent tech documents on their website. So far by following their directions I have been less confused
When you shift to the top ring you are pulling the cable to a limit, that doesn't change the derailleur position by loosening the limit screw , unless you then provide more cable tension - by either expanding the barrel adjuster (like previous poster says) or by moving the shifter ratchet again (if you can).

Good luck ! I farted around with mine until I actually collapsed/crimped a new set of SRAM Flak Jacket cable housing -- a little too much cable tension -- learning the hard way...

Geo

 

[drpimper]

HD Reynolds is exact on his directions on how to adjust a derillueir BUT first thing to do is make sure your front der is on properly


thus meanig:
:from the side view of your chainring the gap from the bottom of your top of teeth profile (big ring) is 3-4mm from the lower edge of outer front der cage.

then from a view from above (way above helps) make sure the outer part of the front der cage is exactly parralle to the outer chainring. THIS IS ESSENTIAL!

To check this I like to rest my forhead on the saddle and stand up from my repair stand, (lazy sitting down while doing this visual check is ususally not accurate.

At the bike shop I work at I see this constantly being a problem. Most other bike shops do not adjust this while building a bike.

From the bike factory the front der. is already put onto the frame. So while most shop employees adjust the limit screw and der cable (some shops don't even to this).

While better shops will first check / remount the front der. and then proceed on with the adustment, after PRE-STRECHING the der cable, so the gear adjustment will not alter after 10 miles of shifting allot. This only applys to using new cables, so you won't have to worry about this step.

Erik "DR. Pimper" DiMarco
[email protected]

 

[wiredued]

This site is helpful
http://www.sheldonbrown.com/derailer-adjustment.html

 

[Bikelyst]

Everyone else is posting what you should do, and all are correct. But if you want to fix the problem easily, just take it to your LBS and have them take care of it.

 

[artemidorus]

Everyone else is posting what you should do, and all are correct. But if you want to fix the problem easily, just take it to your LBS and have them take care of it.

Your LBS is more reliable than mine.