Dismanting Campagnolo Ultra Torque cranks
- Thread starter dennetti
- Start date
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raleighnut
Legendary Member
- Location
- One of the 'Elite'
The bolt on the 'hirth (serrated) coupling' I take it.
Graeme_FK
Veteran
- Location
- Wherever there are sick bicycles
The OP is sorthed but for reference (and info, @winjim) ...
In UltraTorque systems, the Hirth joint is RH threaded in all versions 2009-present, except Ti-axle Super Record versions - you can tell the difference easily, if the circular logo around the central hole in the crank is white - the bolt is normal, RH thread, if it's red, it's LH thread.
Campag made the bolts in Ti different because the thread form used in Ti is different and if they'd left it RH, if users had tried to force a Ti bolt into a steel crank, or a steel bolt into a Ti crank, because of the difference in the thread forms, it will have seized and they'd not have been able to get it tightened, or for that matter, be able to get it out, either ... the basic problem is the way that Ti raises "galls" on other metals when they are (typically) threaded together, and even in Ti / Ti interfaces, a different shaping of the thread is sometimes used to reduce the problem. The small threads on things like derailleur pinch bolts don't cause huge problems but in high-torque, sizeable threads like the Hirth joint, galling can and does produce a problem.
The BB cup thread difference are - BSC, RH thread on non gear side, LH thread on gear side, Italian, both sides RH threaded.
BSC is 1.37" x 24 TPI , Italian in a metric form thread, 36 x 1 mm.
BSC is LH threaded on the drive side to combat thread precession - the tendency of threaded parts that directly interface with a ballbearing system to counter-rotate relative to the direction that the bearing normally rotates in. This is also the reason that LH pedals carry a LH thread. Blame it on the Wright brothers - before they made aeroplanes, they made bicycles and the convention actually stems from them ...
In UltraTorque systems, the Hirth joint is RH threaded in all versions 2009-present, except Ti-axle Super Record versions - you can tell the difference easily, if the circular logo around the central hole in the crank is white - the bolt is normal, RH thread, if it's red, it's LH thread.
Campag made the bolts in Ti different because the thread form used in Ti is different and if they'd left it RH, if users had tried to force a Ti bolt into a steel crank, or a steel bolt into a Ti crank, because of the difference in the thread forms, it will have seized and they'd not have been able to get it tightened, or for that matter, be able to get it out, either ... the basic problem is the way that Ti raises "galls" on other metals when they are (typically) threaded together, and even in Ti / Ti interfaces, a different shaping of the thread is sometimes used to reduce the problem. The small threads on things like derailleur pinch bolts don't cause huge problems but in high-torque, sizeable threads like the Hirth joint, galling can and does produce a problem.
The BB cup thread difference are - BSC, RH thread on non gear side, LH thread on gear side, Italian, both sides RH threaded.
BSC is 1.37" x 24 TPI , Italian in a metric form thread, 36 x 1 mm.
BSC is LH threaded on the drive side to combat thread precession - the tendency of threaded parts that directly interface with a ballbearing system to counter-rotate relative to the direction that the bearing normally rotates in. This is also the reason that LH pedals carry a LH thread. Blame it on the Wright brothers - before they made aeroplanes, they made bicycles and the convention actually stems from them ...
