Torque spec and nut replacement

[OFOAM]

I will be installing risers on my GS as soon as it is warm enough to work in the (detached) garage. I may need to reroute the cables behind the forks. Most easily done by dropping the fork. I believe this entry from the torque specs is for the top nut.
Fork bridge, top, with fork fixed tube, M10 x 1.25
Replace nut
Mechanical thread lock
40 Nm (30 ft-lbs)
Is this the correct spec and why does the nut need to be replaced?
Mick

[marc]

Notice it says mechanical thread lock. That is a nut which isn't round, but instead is oval. It grabs the screw, something like a nylock nut. Every time it is used it becomes less oval and more round, reducing its ability to lock. If you are a dealer you'll replace it every time just to be safe. Ditto with the same kind of nut used to hold the paralever arm to the FD.

You can probably get away with reusing the nut some small number of times. If in doubt, replace it. If it looks round, replace it. If it still looks noticeably oval... your call.