Front derailleur adjustment advice

Grenage

Hi there,

I've watched some videos and read many of the derailleur threads, and while I'm new to bikes, I'd like to think that I'm not being completely stupid - I'm not ruling it out. The chain rubs against the derailleur, and I'm basically trying to correct the issue; this is a bike I was recently given, and have no idea what has been done to the poor thing.

I released the derailleur cable, with the front gear on the smallest cog, and the largest on the rear.
I realigned the derailleur so that it was parallel with the chain.
I adjusted the 'low' limiter, so that the derailleur was a couple of mill from the chain.
I reattached the derailleur cable.
I changed gears, with the front gear on the largest cog, and the smallest on the rear.
I adjusted the 'high' limiter, and got frustrated.

I cannot get the 'high' end to clear the chain, at least, not without rubbing in the lower end. Could anyone make any recommendations on what I might be missing? I know it's not exactly a complicated system, and had I ever owned this bike is a flawless state then things might have been different, but I'm currently feeling a bit obtuse.

The Rookie

Firtsly the cage should be parrallel to the chain when it's mid cassette and middle at the front, otherwise it ends up toeing in or out.

Secondly it's not always possible to avoid some rub in the extremities

Main way to remove rub is via cable tension, play around with it to get the ebst compromise, key to avouid rub in largest ring, smallest sprockets and smallest ring, largest sprockets as they are unique gears, for anything else you can use a duplicate gear that doesn't run

Grenage

Hi there,

Thank you for the advice; I didn't align the cage when the chain was in the middle, so that could be where I'm going wrong. When you refer to the largest and smaller rings, what do you mean? Is that different to the regular gear sprockets?

Chunkers1980

I'd forget aligning it to the chain and align against the big ring on the front.

thelonegroover

The chain ring/wheel refers to the large cogs at the pedal end, the cassette or sprockets usually refer to the rear wheel end. You should avoid runing the large chain ring at the same time as the large sproket on the cassette and vice verser. Not only will it result in premature wear but will be noisy and will rub the mech.

zx6man

As above, the alignment should be to the chainrings (biggest), not the chain.

Shackster

You can't always eliminate chain rub on the front mech in some gear combinations. Here's my way to optimise it (Copied from another post, on starting the set up from scratch):

In essence it boils down to:

1) set low limit screw so that chain just clears mech on granny ring/largest sprocket. Connect cable with moderate tension applied by hand. Sounds like you've done this bit.
2) Attempt to shift to middle ring - if it won't shift up you need more tension in the cable - screw the barrel adjuster out at the shifter. If it shifts up but then the chain rubs on the inside of the mech (while still in largest sprocket) you need less tension, basically because the mech is moving too far with one shift.

When you have done this, and you shift to the smallest sprockets (smallest 2 probably), you will probably get the chain rubbing on the outer side of the front mech. You can't always get away from this, it's up to you to decide whether you'd rather have access to middle/largest or middle/small without rub. You can get the same gear ratios (as middle/smallest) by shifting to the big ring and a larger sprocket.

You might never reach a condition where you don't get the chain rubbing on the mech at one or other side of the cassette. Unless you have a front shifter like the good old gripshift where you can tweak the front mech position whilst riding.

Once you've done this you should be able to shift up to the biggest chainring, and hopefully won't have any chain rub when you are in the big ring and smallest sprocket. If you do you can increase the tension very slightly so it just misses. The high limit screw on the derailleur also needs to be set so it can't shift the chain off the outside.

Done!

Grenage

That's wonderful, thank you all for your advice. I'll get my hands dirty this evening, and hopefully make more progress!

Dirty-Boy

Another good tip. Make sure the height of the front mech is correct, if it's set too high you'll never get it set up perfectly

Grenage

Well I had another bash, and angling the derailleur along the ring, rather than the chain, seems to have helped. There's still a slight rub on the lower gear, but I'll see how it fares tomorrow morning!

thelonegroover

Should we assume this is not a new bike. Have you any idea how old the inner gear cables are. Have you completely removed and relubed the cables. Most gear shifting problems are due to cables. The other setting is the high and low screws. As already advised, try small turns to just stop the rubbing.

Grenage

Indeed, it's at least a couple of years old, but it doesn't look like it's had hard use - just no upkeep.

I haven't lubed the cables, or done too much beyond a clean and oil. I figured I'd ride it for a week or two to get a feel for it again (I've not been on a bike for 16 years), then strip it down to parts and put it back together. I've left half the kitchen on standby.