Front Derailleur

[Mbossa]

I recently changed my bottom bracket to a larger spindle size to accommodate a PAS sensor disc, now my front mech won't reach the large ring. Will I have to change my front mech? I currently have a shimano deore lx mech on a 1994 bike. The original BB had 113mm spindle the new one has 118mm.

 

[Double-E F]

Stupid question perhaps, but did you adjust the cage of the front mech using the screw to compensate for the additional distance?

 

[Mbossa]

Stupid question perhaps, but did you adjust the cage of the front mech using the screw to compensate for the additional distance?

yes but the mech seems too short to reach outer ring, is there longer reach mechs available

 

[Double-E F]

Re:

Normally, the correct combination of BB axle length and crankset ensures that the front mech works properly; I'm not sure if wider range mechs exist..

 

[Mbossa]

Re: Re:

Normally, the correct combination of BB axle length and crankset ensures that the front mech works properly; I'm not sure if wider range mechs exist..

so should I change both crankset and derailleur

 

[Mbossa]

Re: Re:

Normally, the correct combination of BB axle length and crankset ensures that the front mech works properly; I'm not sure if wider range mechs exist..

so should I change both crankset and derailleur

Bottom Bracket shell 68mm

original BB - 113mm

new BB - 118mm

 

[Double-E F]

I'm having difficulty visualizing the situation: how thick is the disc?

Can't you put that on the non-drive side of the crank (or is that a stupid question again..?), does that have sufficient room?

The crank set used determines the BB axle length that should be used, I think the reach of a front mech is more or less standard. So there's no use in changing both crank and mech, I guess..

 

[Mbossa]

I'm having difficulty visualizing the situation: how thick is the disc?

Can't you put that on the non-drive side of the crank (or is that a stupid question again..?), does that have sufficient room?

The crank set used determines the BB axle length that should be used, I think the reach of a front mech is more or less standard. So there's no use in changing both crank and mech, I guess..

Tried that but there was less room on the drive side so the only solution I thought was to get a longer spindle BB, did that and that's where the problem started.

 

[CassidyAce]

Re:

The 1992 Trek 950 had an LX front mech and a long spindle on the BB to cope with some fairly large chain rings. The front mech certainly reached far enough - I just can't remember what the front mech's model number was. I've got one in the garage, though; I'll check.

 

[CassidyAce]

Re:

Just checked. Front mech: FD-M550. It was fine with a BB spindle of 122mm.