Bicycle Mechanics - front derailler limit screws

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BradinMT
08-31-04, 02:50 PM
I just bought a hardly-used Jamis comfort mountain bike off ebay and everything is perfect except the deraillers are a little funky. Is there any explanation for the limit screws not moving the front derailler AT ALL?

Thanks in advance for your input

seely
08-31-04, 03:24 PM
Are you in the middle gear? You have to be in either the highest or lowest gear for the limit screws to have any effect. Don't ask me which does what or anything like that, I just turn them until something moves :D
sydney
08-31-04, 03:50 PM
I just bought a hardly-used Jamis comfort mountain bike off ebay and everything is perfect except the deraillers are a little funky. Is there any explanation for the limit screws not moving the front derailler AT ALL?

Thanks in advance for your input
www.paktool.com has the skinny on deralier adjustment in the repair section.Mindless fiddling usually just makes it funkier.

supcom
08-31-04, 07:26 PM
The high limit screw provides a hard stop so the derailler cannot push the chain outward past the largest chainring or cog. The low limit provides a hard stop so the derailler cannot push the chain off the smallest chainring or cog. These two screws rarely need adjusting and do not affect the shifting between gears.
AndrewP
08-31-04, 08:53 PM
Your problems are most likely caused by dirt or rust interfering with movement of the shifter cables in their housings or under the bottom bracket. Try shifting the gears to the smallest cog then pushing the mechanism to the largest cog, so there is slack in the cable. Then see if you can slide the housing easily over the cable, and if the cable can move easily under the bottom bracket. Cleaning and lubrication may be needed, which will require removing the cables from the der mechanisms.