front derailleur issues

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Moominman2
Posts: 332
Joined: Fri Jul 13, 2012 18:02 pm

front derailleur issues

Postby Moominman2 » Fri Dec 21, 2012 02:42 am

Right,

I was on the turbo and noticed the chain rubbed the front deraileur slightly in a high gear.

Being the silly person I am, tried fixing it. It went terribly wrong, but after watching some YouTube videos,Ii pretty much got back to square one.

What happens now is...

In 10th gear, highest gear on the rear cog (while on the low cog on the front ), the chain catches and has problems staying on the cog.

Also...when changing down from the high cog on the front, it's quite an effort on the shifter. It's not smooth at all.

Anyone know what I can do? Anyone know how much a trip to the LBS will be?

Thanks
Luke

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Monty Dog
Posts: 20382
Joined: Thu Dec 14, 2006 14:31 pm

Re: front derailleur issues

Postby Monty Dog » Fri Dec 21, 2012 08:10 am

Don't try and run the chain in the small sprockets and small chainring - it's called cross-chaining, it's not very efficient and you get chain rub on the inside of the big chainring. Front mech position and alignment is critical - this is where most people get it wrong: Outer cage needs to clear the big chainring by 1-3 mm and set parallel to the chainrings. Next set the low and high stop screw positions, finally adjust the cable to get it moving sweetly. Your LBS will probably charge about 20 minutes workshop time, so £10-20.
Make mine an Italian, with Campagnolo on the side..

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smidsy
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Joined: Tue Jan 17, 2012 20:52 pm

Re: front derailleur issues

Postby smidsy » Fri Dec 21, 2012 08:28 am

There are effectively only 3 adjustments you can make.

1. Cage height/alignment with chainring - should be parallel and have 1-2 mm clearance above highest tooth.
2. Cable tension - should be tight when on the small chainring.
3. High/Low screws - these need to be 'fettled' so that there is 1mm clearance between the inside of the mech plate and the corresponding chainline when on each chainringl. Plenty of vids on this.

The above can be tricky (especially on Shimano 10 speeds for some reason) as they seem very particular on front mech adjustment.

If it all goes pear shaped just put the screws back in, disconnect the cable and start a fresh.

Some set ups will never remove rubbing on full cross-chaining (e,g big ring on front and big cog on back) no matter how much you adjust things. Cross-chaining is best avoided anyway if you want to prolong component life.
Yellow is the new Black.

Moominman2
Posts: 332
Joined: Fri Jul 13, 2012 18:02 pm

Re: front derailleur issues

Postby Moominman2 » Fri Dec 21, 2012 09:52 am

Thanks for the info guys. Really useful. I'll leave it how it is now and then get it sorted by my LBS along with a few other things.

Cheers
Luke


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