Is the torque on a nutted bottom bracket different than a bolt-onbottom bracket?

TomYoung

Hi all:

The bottom bracket on the bike I'm fixing up for my daughter uses a
nut instead of a bolt to secure the crank to the square taper axle. I
seem to recall that torque values on nutted bottom brackets are
different (higher?) then the torque typically used on bottom brackets
that use bolts, but I'm not finding anything that confirms this. All
the torque value tables I've found just specify "bolt" bottom bracket
torque but don't mention "nut" torque.

Is my recollection wrong?

TIA

Tom Young

Mark

TomYoung wrote:
> Hi all:
>
> The bottom bracket on the bike I'm fixing up for my daughter uses a
> nut instead of a bolt to secure the crank to the square taper axle. I
> seem to recall that torque values on nutted bottom brackets are
> different (higher?) then the torque typically used on bottom brackets
> that use bolts, but I'm not finding anything that confirms this. All
> the torque value tables I've found just specify "bolt" bottom bracket
> torque but don't mention "nut" torque.
>
> Is my recollection wrong?

My dim recollection is that "nut torque" was spec'd /lower/ than "bolt
torque" for BB spindles, but it's been so long since I've seen the spec,
I wouldn't depend on that recollection.

Mark J.

jobst.brandt@stanfordalumni.org

Tom Young wrote:

> The bottom bracket on the bike I'm fixing up for my daughter uses a
> nut instead of a bolt to secure the crank to the square taper axle.
> I seem to recall that torque values on nutted bottom brackets are
> different (higher?) then the torque typically used on bottom
> brackets that use bolts, but I'm not finding anything that confirms
> this. All the torque value tables I've found just specify "bolt"
> bottom bracket torque but don't mention "nut" torque.

> Is my recollection wrong?

All high quality BB spindles I have seen use bolts and have a through
bore while less expensive spindles are black, have poorly finished
bearing races and possibly are poorer material because heat treating a
piece of varying cross section is less practical. Torque, if
different, would reasonably be lower than with bolts for two reasons.

If a bolt breaks the stub can readily be removed and a new high
quality bolt used. The threaded extension of a one piece spindle is
most likely not as strong and if it fails the spindle is scrap.

Jobst Brandt