Lug nut thread engagement

[BigBlockOlds]

How much thread engagement is considered safe? I have a set of TTII Classic wheels, Kore3 billet aluminum hubs w/ stock length 12mmx1.5 studs and C5 rotors. I know the rotors throw everything off by about a .25" or so and have heard people say longer studs are necessary but I have at least 10-12 full lug nut revolutions before even touching the wheel.



Would this be considered okay?

Thanks,

[fast Ed]

10 - 12 turns should be fine. Generally the mininum requirement for thread engagement is equal to the diameter of the stud. So at least half an inch of thread engagement should be present.


cheers
Ed N.

[parsonsj]

I checked. 10 revolutions of lugnut on 12x1.5 stud equals about 0.750 (16 mm) of thread engagement.

You'll be fine.

jp

[Damn True]

Basic aviation fastener rule of thumb: There shall be a minimum of 2-3 threads exposed when the nut is torqued in place.

....and JP is right.

[BigBlockOlds]

Cool. Thanks for the help!

[Rick Dorion]

Basic aviation fastener rule of thumb: There shall be a minimum of 2-3 threads exposed when the nut is torqued in place.

....and JP is right.

Is that for visual inspection needs? Or stress points?

[Damn True]

Inspection is a part of it. Makes it easier for a crewman to visually confirm that a fastener is correctly in place. All bolts are sized such that 2-3 threads will protrude. If you see more, the bolt is stretched or the wrong size, if you see too few the fastener is backing off.

There is also, and IMO this is the more important point, an issue with the distribution of load. If all 20 or so threads on the inside of a nut are engaged onto the bolt the load is distributed as equally as possible and each thread is seeing as little individual load as possible. If there are not 2-3 threads exposed then the top 2-3 threads on the nut are engaged with the tapered portion of the threads on the bolt reducing the surface area in contact with the nut.

Same is true of castelated nuts and self locking fasteners like jet-nuts.

[6'9"Witha69]

NHRA and some sanctioning bodies require open ended nuts with protrusion of the bolt to ensure adequate load.

[parsonsj]

NHRA and some sanctioning bodies require open ended nuts with protrusion of the bolt to ensure adequate load.

Very true. My lugnuts are close-ended, and I worry about passing tech every time. So far, no problems.

jp

[CarlC]

As noted above 2 threads minimum of exposed thread when using a nut. In reality +90% of the tension load is held in the first three threads of the nut.

For blind holes a minimum of 1.5X thread diameter of engagement is considered normal.