markjenn said:
The torque on this axle nut is what causes the entire axle assembly (axle, spacers, inner bearing races) to behave as one unitized assembly on which the wheels rotate on the bearings. The forces are immense and you don't want this assembly to have any looseness or movement due to torque and road impact.
While the axle nuts are an area I do always use a torque wrench on, (dry threads), I make sure my axles are lubricated, not the threads. Just a thin smear of moly grease, though any grease would work fine. They do grease them at the factory for assembly, though typically it's the Yamaha standard of barely enough to do the job.
In response to Mark's comment above that I quoted; I do agree that the parts behave as one unitized assembly. I disagree that the this is a function of the torque value given to the nut. If it's 'tight', there is no significant slop in the assembly. Torquing it higher isn't going to change that. There isn't anything in that assembly that tapers or would change. The wheel bearings and spacers fit over the axle that slides though them. They will spin on the axle in some circumstances, but those are uncommon. (seized bearings)
Hopefully the people reading this thread understand that the correct tightening procedure is to insert the axle, spin the nut on, tighten the nut using two tools, one on the nut, another on the axle, then when you are satisfied with how tight the nut is, lastly tighten the pinch bolt in the swing arm, (or the pinch bolts in the forks for the front). The pinch bolts are
NOT there to hold the axle while you tighten the nut! (or when you loosen it!!)
When people attempt that, its not uncommon to find the pinch bolts abused and also to find that the axle was not correctly/fully seated into the assembly, (as others have mentioned already).
I've had a '12 and now a '15. The OP pictures show a nut that does not look like either of my OEM rear axle nuts. Neither of mine have had those small slots cut into the flats. This makes me wonder if the OP is the original owner of the bike, and if he has two or more bikes that were being worked on at the same time. While it's completely possible that several different vendors are used by Yamaha for this part and it
is the OEM nut, I can't help but wonder of at some point in time the incorrect nut was installed on the axle, (different bike's or non-OEM).
I have known a couple of riders that forgot to torque the axle nut, or tried to use the pinch bolt to hold the axle while torquing the nut, and subsequently had the nut fall off during a ride. ???