Front derailleur adjustment question

[bigphil]

Hi,

Hope this is right place to ask. I have looked through the howtos but can't see the right section for my problem.

I have a bike with a Shimano FD-M191 front derailleur which needs some adjustment. When I change up from the smallest gear to the middle one, the chain almost makes it but then doesn't, falling back to the smallest cog again and then making a loud rattling sound. The only way I can change up from the smallest to the middle gear is to "pretend" to change up to the biggest gear, then stop, allowing the chain to settle on the middle gear.
Changing from the middle gear to the largest works fine, if that helps.

There are two screws on the derailleur itself, but the old maxim of a little knowledge being a dangerous thing seems to apply here, so I am hoping someone with more experience will be able to help.

Thanks in advance.

Cheers,

Phil

[DaveM]

What you descibe usually means the shifter cable needs more tension. There should be a barrell adjuster where the cable comes out of the shifter. Back this out in small increments to see if it improves the shifting. The two little screws set the limit for movement of the derailleur to the inside and outside. They shouldn't affect shifting to the middle ring.

If this doesn't help. Check also that the outer edge of the derailleur is parallel to the chainrings and that the derailleur isn't sitting too high (it should have only 2-3 mm of clearance above the large chainring.)

http://bikeride.com/adjust-front-derailer/