Quote:
Originally Posted by SPYDERLK
What you are seeing there is a settling into the hub of the lug and the wheel, not a stretch of the lug. Otherwise yould be seeing engine bolts requiring re torque. Head bolts can benefit cuz of gasket settling, but metal to metal like rods and mains dont need it.
larry
I can't argue with that, so I'll consider it as probable as the bolt stretching explanation. Possibly it's some of both.
Usually the wheel to hub interface is metal to metal, as is the lug nut to wheel interface, right? How does this fit in with your assessment?
Might we consider that the metallurgy of rods and their bolts may be different than that of lugs and wheels? Also that lugs as typically installed have a wheel thickness's worth of space between the nut and the hub in which the threads are not engaged, and that rod cap bolts do not? Might these differences add up to the possibility that there is some lug stretching going on?
Well, either way the result is the same. Re-torque and THEN put on a dab of paint.
No doubt, with a new stud and nut, both are a factor, but the stud-nut component is vanishingly small in comparison to component settling. In steel, the crystal slip planes are inhibited by carbon. ... So when loaded in one direction to near yield there is some very small movement as the keying effect jams tight. Once this extremely small plastic deformation happens the stud becomes tensily elastic at that length up to very high stresses. It is
not elastic at those stresses when put under
cycles of alternating compression and tension. It works this way for torsion as well. Bolts therefore can undergo some small damage on repeated usage if high reverse torque is needed to crack them loose for removal. With very highly stressed bolts this can become critical in a few twisting cycles.
....Settling OTOH is huge in a new assembly when all important factors have not been controlled; *studs are pressed into the carrier leaving residual compression and accompanying diametral expansion in the press fit area, *the stud may not reach, or may rebound slightly from the pressed position, *the wheel is not formed accurately to fit exactly and settle uniformly against the hub, *there is probably
paint on it, * the taper sockets for the lugs have not been stressed to cause the slip plane keying, *etc. Using the stud to draw in and clamp, and then follow on use to facilitate settling puts the system into stable conformation where torque/preload wont change w/o rotation on the threads. If a wheel or stud is replaced, do it again. ... Systems that must rely on first stress cycle stability are extremely well controlled in manufacture and assembly.
....Yeah, but all bolt fastening systems that clamp tight will have a clearance hole in at least one piece.
larry
