Front Mech Rubbing

[Nickj6]

Hi all

My chain was rubbing on the front mech, so I researched set up guides and adjusted the height and angle of the front mech. I have Shimano throughout and its a compact system, (2 rings on the front) on the top ring I have no rubbing across the rear selection. However if I move to the lower front ring i get rubbing across the lower 3 (8th,9th & 10th) gears. I have recently moved from an 11/25 rear cassette to a 11/28 cassette, with a new chain. The bike is only 3 months old with around 500miles on it.

Is it normal for the chain to rub?

 

[boydj]

It's difficult to get the front mech set up with no rubbing at all, which is why top-end systems all have a 'trim' feature. It should be possible to get a set-up with no rubbing in the useable gears, as long as you avoid the extremes of cross-chaining. Personally, I tend to use no more than 7 of the cogs with either chainring and shift chainrings in preference to using the outer or inner cogs.

 

[fossyant]

Its normal you cant get the last 2 or 3 without trim. Its also a warning the chain is not running straight enough. On the small front, dont use the smallest 2 or 3 sprockets, on the big front chainwheel, don't use the biggest 2 or 3 sprockets.

 

[Nickj6]

Thanks for the replies, I can use all the rear sprockets on the large front chain wheel, however on the rear I am rubbing I never noticed it before its slightly annoying to be honest.

 

[SpokeyDokey]

Thanks for the replies, I can use all the rear sprockets on the large front chain wheel, however on the rear I am rubbing I never noticed it before its slightly annoying to be honest.

As per a previous post - do you use the trim function?

 

[fossyant]

Dont use all the sprockets. You will have a gear overlap. Using the extreme of gears introduces big bends into the chain, and promotes wear.

 

[Nickj6]

As per a previous post - do you use the trim function?

I am quite new to road cycling, whats trimming?

 

[SpokeyDokey]

I am quite new to road cycling, whats trimming?

Most decent groupsets have a small subsidiary shift that moves the FD a small amount without fully initiating an up change or down change.

This usually eliminates any FD rubbing on both rings in-extremis at the rear.

What shifters/FD do you have?

 

[Nickj6]

Most decent groupsets have a small subsidiary shift that moves the FD a small amount without fully initiating an up change or down change.

This usually eliminates any FD rubbing on both rings in-extremis at the rear.

What shifters/FD do you have?

The groupset is a mix of Shimano's 10 speed 105 and Tiagra groups featuring, Tiagra 10 speed integrated brake and shift levers, Tiagra front derailleur, 105 rear derailleur and a 105 rear cassette ​

 

[SpokeyDokey]

The groupset is a mix of Shimano's 10 speed 105 and Tiagra groups featuring, Tiagra 10 speed integrated brake and shift levers, Tiagra front derailleur, 105 rear derailleur and a 105 rear cassette

Try this:

shift from small chainring to large - push the big lever all the way across till it stops

now push the small lever gently until it clicks - the FD will move inwards slightly but not onto the small chainring it has now been trimmed and should help eliminate rub on the large chanring/bigger cogs combos

ditto:

shift from large chainring to small

now push the big lever gently until it clicks - the FD will move outwards slightly but not onto the large chainring it has now been trimmed and should help eliminate rub on the small chanring/smaller cogs combos

***

This function is subject to a set of adjustments just like indexing - the exact details will be in Shimano Tiagra Techdocs eg:

Bottom right of page...

http://techdocs.shimano.com/media/t...FD-4503/SI_5K80A_En_v1_m56577569830606982.pdf

 

[Nickj6]

Thanks for the advice I will give it a go tomorrow.

 

[SpokeyDokey]

Thanks for the advice I will give it a go tomorrow.

Good luck!

 

[RecordAceFromNew]

Hi all

My chain was rubbing on the front mech, so I researched set up guides and adjusted the height and angle of the front mech. I have Shimano throughout and its a compact system, (2 rings on the front) on the top ring I have no rubbing across the rear selection. However if I move to the lower front ring i get rubbing across the lower 3 (8th,9th & 10th) gears. I have recently moved from an 11/25 rear cassette to a 11/28 cassette, with a new chain. The bike is only 3 months old with around 500miles on it.

Is it normal for the chain to rub?

Imho it is not normal to rub on three consecutive sprockets. In case there is any confusion, I presume the rubbing happens when you are on the small front ring, and with the smallest 3 rear sprockets.

There can be various reasons, e.g. the front mech is not parallel to the front ring (you can check by looking from above, especially if you have been adjusting the vertical location of the mech), or more likely the mech's L limit screw is not set correctly. The latter would be the case if you can see more than 1mm of clearance between the chain and the mech's inside cage when the chain is on small front large back. If you can see 2mm or more from above, then it would most certainly account for the chain rub you are seeing. If it is indeed over 1mm, the L screw needs to be turned clockwise until it is. It is best to do it by trial and error, turning the screw little by little only when the mech is on the large front ring - or else it is easy to damage the head of the screw.

 

[Nickj6]

Hi

All thanks the for the all the advice, the trim feature works a treat (feel a little silly now.) One last question though on the front small ring and the rear small ring the chain starts to catch on the lifting rivet on large front ring, there does not look like away to adjust this so I think it is how it is.

Thanks again all

 

[SpokeyDokey]

Hi

All thanks the for the all the advice, the trim feature works a treat (feel a little silly now.) One last question though on the front small ring and the rear small ring the chain starts to catch on the lifting rivet on large front ring, there does not look like away to adjust this so I think it is how it is.

Thanks again all

What do you mean by 'lifting rivet'?