Having issues with sorting out gears

scally56

After respraying my bike i'm putting it back together and i can't for the life of me get my front derailuer working how it should do. its double ring and the chain is sitting on the inside ring. when i move it to the outside ring it rubs against the derailluer. I've looked on parktools and can't really understand what they are on about. I've tried the tension screws, one seems to move the railluer backwards and forwards and the other seems to do nothing. Any help would be great. I've not even started on the rear yet, oh dear!

Cheers

scally56

just realised that i've not given much information about what comps i have. its a shimnao front derailuer

geoff_ss

It's obviously not moving far enough. Assuming it's a tight cable for highest gear (ie low normal) then perhaps you haven't tensioned the control cable enough for the shifter to move into the high gear position.

You might also not have the derailleur low enough down the seat tube.

Geoff

JWSurrey

Geoff's cable tension suggestion is what I'd put my money on - just one other thing to check - that the cage is parallel to the chainrings.

nmcgann

Also check you attach the cable correctly to the front mech. On some mechs you can clamp the cable in more than one position. Choosing the wrong one changes the distance the mech moves per shift lever click and the indexing doesn't work properly.

Try again and get your head around the park tools info, or look at the Sheldon Brown site - there's good advice out there.

Neil

oldwelshman

Put the bike in a bike stand and rotate the cranks, then change gear py pulling on the gear cable under the downtube, not using the STI's. If it still does not go on big ring it is not tension but the outer limit screw. Once you have set the limiy screws correctly then you can check the tension.

Monty Dog

Getting the position & alignment right is critical - as well as being parallel to the chainrings, the bottom of the outer cage plate should clear the big chainring by about 1-3mm. Release the cable clamp and screw any cable adjusters right in. Release the ratchet in the gear lever by moving the inner lever a few times. Reclamp the cable - make sure it runs clearly in the BB cable guide - there should be no slack, but no tension when in the lower position. Put the rear gear in the largest sprocket - and adjust the lower stop screw such that the inner plate is about 1mm clear of the chain. Try and shift to the outer chainring - unscrew the upper stop screw if it doesn't move far enough - if the screw is in the right position, then try turning the cable adjuster a turn at a time to give more 'pull'. When in the smallest rear sprocket and the big chainring, there should be no rubbing - adjust the stop screw accordingly. Work all gear combos to check it's working OK - you should expect some chain rub when in the small sprocket/large chainring - this is normal for modern drivetrains