Front deraileur

AaronB

Just wondering can anyone offer some help.
Since the bike shop swap out my 12-25 for a 12-27. I have a compact.
On the top chainring and 9 (small ring) its rubbing off the front deraileur. And the same when im climbing in the bottom chaineing and 1 ( large ring)

Whats the best way to tweak it?

bcmf

Put the gearing in front small and rear biggest.
There are 2 screws on the top of your mech. Of them will be tough (have resistance) to adjust. Uncsrew it by a quarter of a turn and see then turn the pedals. See how it is then. repeat until the chain is just barley clearing the front mech.
Then change the gearing to Big Front Smallest rear. Repeat as above but with the other screw.
HTH

AaronB

ok thanks, will give it a try tomorrow.

AaronB

im having a problem now with the rear deraileur now. the top ring on the back is making the deraileur jump, since its a 27 now not 25 so i adjust the b-tension abit and it has stopped but now gear changes are crap mainly on the smaller ones trying to adjust with the two screws and cable tensioner but its abit better now. needs more tweaking.

abit of a noob when it comes to these little tweaks.

bcmf

You can over do it when adjusting the rear mech.
Best way is to put the shifter to the smallest cog position.
If the chain sits snugly on the smallest sprocket then good.
Now turn your adjuster screw clockwise (the ajuster screw is where the cable enters the mech at the back)about 1 and a half turns. Now try and shift to the nxt smallest cog with your shifter.
If it doesnt go up but the chain chatters turn the screw slowly anti-clockwise slowly until the chain moves up and sits neatly and quietly.
Now try and drop the shifter back to the smallest cog.
At this point very small adjustments are all that is needed on the adjuster.
If the chain 'hesitates' just turn the screw 1/4 of a turn at a time till it drops neatly.You should have a nice clean crisp shift.
It sounds like your cables have stretched after bike shop was working on the bike.

AaronB

yup i did that, but thats not the problem. if i can get it sitting nicely on the bottom it wont go on to the top ring. its like the arm needs to push the chain up more. If i adjust it with the adjuster i can make the chain jump up and down between rings no problem.

i think i need to just the arm abit more, if i cant get it i will bring it back to the shop.

bcmf

AaronB wrote: »

if i can get it sitting nicely on the bottom it wont go on to the top

If we are talking about the Rear Mech....If it wont go to the top then either
A) the limit screw screw is stopping the mech from going up
or
and I am suspecting this is more likely form the sounds of it......whoever set the rear mech set it by not setting the shifter to the smallest cog then made the tension adjustments on the cable. This will cause all sorts of weird problems and is easy enough to fix.

AaronB

Well spent 3 hours this morning working on the bike, i had to redo the front & rear deraileur, now the gears are smooth and crisp actually better then it ever was from new.

I have these videos online that helped alot, here they are incase anyone else would like to make use of them

http://www.youtube.com/user/sweetsbench/videos?view=0

thanks for all the advise guys.