Ok so I have finally started building up the 456. The plan is to try and use the majority of the parts off another bike.
I have read some comments on here about 456 chainstay clearance issues.
The BB I intend using is a mid 90s square taper 68mm shell. Can't be sure of the axle length till I take it out the old bike. Cranks are LX same vintage. Can anyone confirm it will fit or what length axle it needs to be etc?
And if I need a longer BB will that affect chainline or do I not need to worry about that running gears (will be 21 speed retro loveliness to start with!)
IIRC something like a 113mm square taper UN54 BB will give a 50mm chainline which is the minimum needed on the 456. A 68mm shell is correct.
That's helpful thanks. 113mm rings a bell, may be in luck
Bike upside down, measure from centre of BB shell to centre of middle ring = chainline dimension (stands to be corrected, look on Sheldon's site for far better info than my paraphrasing).
IME, 50mm chainline with a Summer Season 456 and a 36T middle ring was too tight. Well, it wasn't but when the chain did come off / shucked the resulting wedge was a f&*king nightmare. Happened a few times. The wedging problem was mostly due (IMO) to the fag paper clearance between middle ring and chainstay.
And before anyone shouts, yes, I know chainschuck isn't a direct result of frame design etc etc etc.
Brant did recommend a bodge of crimping / crushing the chainstay to increase clearance. Know someone that did it on a regular 456 and thinks it was worth it.
middle ring will be 32 so more clearance hopefully
axle length depends on the cranks. Most modern stuff sits fine on 113mm but I had an old 90s LX crankset (93/94 maybe?) and it needed 120mm BB on my inbred. In fact 122mm prob would have been better as there was bugger all clearance between the small ring and the chainstays. Now running 113mm BB with some (slightly) newer cranks on the same frame and there is plenty clearance, if anything too much (front mech has trouble reaching the big ring with the limiter screw all the way out).
Anything wrong with using two spacers on the BB on the driveside btw?
[i]Anything wrong with using two spacers on the BB on the driveside btw? [/i]
I did on mine and it seemed to work OK.
