Thread engagement and Al lug nut warning.

[NightmareMoon]

We had an S197 loose a wheel on the first turn at a local autox. I though it was a lesson worth learning from.

The guy was trying stock studs and a ~10mm spacer, which only allowed ~4 turns of lug nut engagement and he was using aluminum tuner style lug nuts.

Moments before, he had even asked an experienced autocrosser how many thread engagements he needed minimum and then disregarded the advise. "It'll probably be fine"

Yep, first hard turn and the wheel went a rolling while the car slid 50 feet on the subframe and front rotor. Ouch. The partially engaged aluminum lug nuts stripped. Shortly afterwards you could hear the sounds of torque wrenches clicking throughout the pits like crickets on a summers evening, nobody wanted to repeat that kind of mistake.

So yes, when they tell you that you need at least 6 turns of thread engagement, you do. And please leave the lightweight tuner lug nuts at home and use good steel parts. Wheel fasteners aren't probably the best place to try to save a few oz.

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[steveespo]

A lug nut should engage the stud a MINIMUM of the diameter of the stud. So for a 1/2"-20 stud you should engage 1/2" or 10 full turns of the nut. And keep the anodized aluminum nuts for hard parking.

 

[ANGST]

I didn't even know aluminum lug nuts were a thing !

How does anyone think that's a good idea ?

 

[tom_sprecher]

A lug nut should engage the stud a MINIMUM of the diameter of the stud. So for a 1/2"-20 stud you should engage 1/2" or 10 full turns of the nut. And keep the anodized aluminum nuts for hard parking.

^^^ This. Ever notice the height of a standard nut is equal to the diameter of the bolt it threads onto?


And who ever thought aluminum lug nuts was a good idea?

 

[ANGST]

How many thread on a lugnut should be engaged on the bolt ?

...All of them

 

[sigintel]

Aluminum lugnuts? Thats insane.

 

[plc268]

I didn't even know aluminum lug nuts were a thing !

How does anyone think that's a good idea ?

Most of them are for looks. Those fancy looking lug nuts you see, usually aluminum.

Most people who buy these don't really have a clue and generally aren't buying them for weight savings.

If you were really trying to save every last ounce, then titanium lug nuts are a thing. They require some special considerations with installing (requires anti sieze and different torque specs) and are expensive. But most people aren't going to chase a few ounces of rotating mass like that.

 

[zhent]

I was there. It was hell to watch, but the lessons learned for all in attendance were invaluable. I have my track tires on stock wheels and use open ended acorn nuts, so that I can always tell where the lugs are in relation to the studs. Yes, I torqued my lugs that morning, and aluminum lugs nuts would never even have been a thought.

 

[NavsENG]

I've made and run aluminum lugnuts on my track car with no issues. Though I would never run with less than 2xD of engagement. I have closer to 1.5" of thread on mine. Lots of vintage mustang track guys run the aluminum lug nuts and I have never seen an issue.

Honestly there is little to no weight savings at this point , they just "look cool"

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