Front derailleur not reaching largest chainring

[2manyoranges]

Re:

Hi Alison - you’ve covered most bases - you know about end stop screws so you’ve ruled that out. People have mentioned bb axle length and that’s in your sights. A couple of other things though...

What kind of clearance on the chain stay do you have re small chain ring? If lots (and there are plenty of photos on t’web to compare yours with) then bb too long.

But also...what bike is it? And is it 73 or 68 bb shell? A 68 bb in a 73 shell will really mess everything up in the manner you describe.

Oh. And doing it with just your hand without a cable can be deceptive, they can bloody hard to move right outwards.

And another thing, if the cage has been whacked, the axles can be bent and restrict movement.

And another thing...I had a mech once which had unbeknownst to me a bent actuator arm, which fouled the seat-tube grrrrrr

 

[Alison]

Re: Re:

Hi Alison - you’ve covered most bases - you know about end stop screws so you’ve ruled that out. People have mentioned bb axle length and that’s in your sights. A couple of other things though...

What kind of clearance on the chain stay do you have re small chain ring? If lots (and there are plenty of photos on t’web to compare yours with) then bb too long.

But also...what bike is it? And is it 73 or 68 bb shell? A 68 bb in a 73 shell will really mess everything up in the manner you describe.

Oh. And doing it with just your hand without a cable can be deceptive, they can bloody hard to move right outwards.

And another thing, if the cage has been whacked, the axles can be bent and restrict movement.

And another thing...I had a mech once which had unbeknownst to me a bent actuator arm, which fouled the seat-tube grrrrrr

I've checked the bottom bracket casing and it says 72,9 so I assume it's a 73mm casing the bike is a '93 Specialized Rockhopper so is this the problem, but what axle length should I get?

Alison

 

[Splatter Paint]

Re:

Tech docs say.... FC-M560

47.5mm chain line = 113mm BB
50.0mm chain line = 118mm BB

I would suggest if a steel frame then 113mm or 118mm if aluminium. However, I don't see that the BB is the issue here.

Have you measured from the centre of the seat tube to the middle ring? This will determine the existing chain line.

SP

 

[2manyoranges]

Re:

sorry to drone on, but of you are trying to fit say a 114 axle length bb for a 68 shell in a 73 shell, this will throw the cranks right outwards - by around 3-5mm depending on axle length.

See

https://www.sheldonbrown.com/bbsize.html

All shimano square taper bbs are labelled 68 or 73, they are not interchangeable re chain line (and therefore front mech clearance).

Modern BBs have spacers - one on one side and two in the other for 68 and only one on drive side alone for 73mm.

Sorry, it's just a reality.

 

[Scvintage]

Re:

Probably stating the obvious, but is front derailer too high or low on seat tube? Up/down location

 

[Alison]

Re: Re:

sorry to drone on, but of you are trying to fit say a 114 axle length bb for a 68 shell in a 73 shell, this will throw the cranks right outwards - by around 3-5mm depending on axle length.

See

https://www.sheldonbrown.com/bbsize.html

All shimano square taper bbs are labelled 68 or 73, they are not interchangeable re chain line (and therefore front mech clearance).

Modern BBs have spacers - one on one side and two in the other for 68 and only one on drive side alone for 73mm.

Sorry, it's just a reality.

I have now ordered the correct size BB I hope this will fix my problem

Thanks for your help

Alison

 

[Alison]

Re: Re:

Probably stating the obvious, but is front derailer too high or low on seat tube? Up/down location

I place it so the derailleur is a penny's depth from the largest chainring, has always worked in the past

Alison