I'm about to install a new Shimano 7610 Track bottom bracket - this is the BB for the older generation square taper D-Ace track cranks. The BB is English sized going into an English BB shell. Having installed the drive side cup and BB unit and torqued it to 50Nm, I'm having a problem with the left side cup - it screws in ok most of the way but then stops approx 1-2mm short of its full insertion, ie when tightened there's a 1-2mm gap between the left edge of the BB shell and the l-hand cup. It's not a question of further tightening because the axle starts to bind if tightened any further. The left hand cup does come with a rubber o-ring which suggests that this gap might be intentional and needs to be covered with the o-ring, but this seems like a strange design if that's the case. Removing the BB and comparing its overall width to the BB shell, it does seem that the BB-plus-cups is 1-2mm wider than the BB shell. The BB is definitely English (cups are English threaded and BB body has NJS logo).
Is this normal for this BB or am I missing something? If it is normal, how hard do I need to torque the l-hand cup to ensure it's a tight enough fit?
I'm about to install a new Shimano 7610 Track bottom bracket - this is the BB for the older generation square taper D-Ace track cranks. The BB is English sized going into an English BB shell. Having installed the drive side cup and BB unit and torqued it to 50Nm, I'm having a problem with the left side cup - it screws in ok most of the way but then stops approx 1-2mm short of its full insertion, ie when tightened there's a 1-2mm gap between the left edge of the BB shell and the l-hand cup. It's not a question of further tightening because the axle starts to bind if tightened any further. The left hand cup does come with a rubber o-ring which suggests that this gap might be intentional and needs to be covered with the o-ring, but this seems like a strange design if that's the case. Removing the BB and comparing its overall width to the BB shell, it does seem that the BB-plus-cups is 1-2mm wider than the BB shell. The BB is definitely English (cups are English threaded and BB body has NJS logo).
Is this normal for this BB or am I missing something? If it is normal, how hard do I need to torque the l-hand cup to ensure it's a tight enough fit?
The gap between the flange on the left adapter cup and the face of your bottom bracket shell is entirely normal for this bottom bracket model. Its design accommodates the common window of variations in shell widths from the nominal 68 mm. As you intuit, the supplied O-ring will help protect the exposed face of the shell since the left cup flange doesn't make contact with it.
Shimano literature indicates a torque range of 50 to 70 Nm for installing these cartridge style crankbearing units.
------------------------------- John Dacey Business Cycles, Miami, Florida Since 1983 Comprehensive catalogue of track equipment: online since 1996 http://www.businesscycles.com -------------------------------
I'm about to install a new Shimano 7610 Track bottom bracket - this is the BB for the older generation square taper D-Ace track cranks. The BB is English sized going into an English BB shell. Having installed the drive side cup and BB unit and torqued it to 50Nm, I'm having a problem with the left side cup - it screws in ok most of the way but then stops approx 1-2mm short of its full insertion, ie when tightened there's a 1-2mm gap between the left edge of the BB shell and the l-hand cup. It's not a question of further tightening because the axle starts to bind if tightened any further.
Tightening the cup should not cause the BB to bind. It is like most all other cart bearing shimano BBs, but with steel cups. I would chase the frame BB shell threads and face the right side of the BB shell. It should not bind regardless of how tight the cups are.
Quoted message said:
The left hand cup does come with a rubber o-ring which suggests that this gap might be intentional and needs to be covered with the o-ring, but this seems like a strange design if that's the case. Removing the BB and comparing its overall width to the BB shell, it does seem that the BB-plus-cups is 1-2mm wider than the BB shell. The BB is definitely English (cups are English threaded and BB body has NJS logo).
Is this normal for this BB or am I missing something? If it is normal, how hard do I need to torque the l-hand cup to ensure it's a tight enough fit?
That's interesting - the axle starts to bind well before the tightening torque on the l-hand cup approaches 50Nm - more like when its at 20-30Nm. The threads do seem reasonably good when threading either side cup on its own, and the cup flanges look parallel to the BB shell, at least to the naked eye, but I presume we're talking pretty very tolerances here...
I'll find a suitable LBS / frame builder and ask them to chase & face the BB shell.
