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Minimum Tire Lug Thread Engagement

6K views 32 replies 16 participants last post by  VTBilllet 
#1 ·
After buying a set of new 16" 11" wide Bogart D-10 rear rim's and installing a 7/16th spacer due to tight tire clearence with the leaf springs, I noticed the lug's only go on a total of 6 turn's on the stock studs for a 2004 Lightning. They are open ended lug nutz that sit flush with the end of the stud when installed and torqued down (see pics). They torque up to spec, and seem very sturdy.

I heard the rule of thumb is that 2 threads should be showing thru the end of the lug nutz when properly torqued (using 100 ft lbs). I don't want to wreck myself , someone else, or the truck over something as basic as some lug's nut's that aren't engaging the thread's enough.

Seems like its on the minimum verge of being safe. Any thoughts?

Thanx

JT
 

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#2 ·
im pretty sure its either ihra or nhra rules or maybe both say that the stud has to come out so far past the lugs... i think its twice the with of the stud... that was the rule a long time ago. either way they dont work on your truck so just send me those useless wheels and il put them to use lol
 
#4 · (Edited)
From the NHRA rule book
The thread
engagement on all wheel studs to the lug nut, or lug bolt to wheel
hubs, must be equivalent to or greater than the diameter of the
stud. Length of the stud/bolt does not determine permissibility;
length of the engagement between the stud and lug determines
permissibility.
 
#5 ·
WTF? In plain english........(BTW, thanks for the quote, just wish I was smart enuff to understand what it's trying to say) :smt102 I finished in the bottom 15% of my high school class, but I did have good hand-eye coordination.
 
#7 ·
damn it man if you have to get longer studs... thats a job in itself. looks like your in the market for some slightly narrower tires
 
#9 ·
on aircraft... military aircraft capable of going Mach 2.5 and 9+ G's... rule is ALL hardware must protrude 2 to 3 threads past surface!
:smt102
 
#10 ·
The tech guys at my local track simply stated that the lugs had to extend past the nuts. If you're running slicks you're also required to use open ended lug nuts such as the ones you have pictured as well vs a set of closed ended such as the oem nuts. Open ended nuts aren't a requirement if running DOT tires but then the tech might want to inspect all of your lug bolts in order to ensure they're of a proper length so why chance it.

Roach
 
#12 ·
As long as all the threads in the nut are engaged, you are fine. Should be fine with NHRA too. If there is any doubt, take your spacers to a machine shop and have them mill them down 1/16"-1/8"
 
#14 ·
The rule means that if the stud is 1/2 thick that is how much must stick out past the lug nut. If the stud is 14mm thick (.55 inches), then 14mm 0r .55" must be visible past the nut.
 
#15 ·
engagement does not mean protrusion. i disagree with your interpretation, respectfully of course.
 
#28 ·
These 16x11 bogarts have a set of 30/14.5-16LT M&H cheater slicks on them and they have about a thin slice of bread clearance on the leaf springs without a spacer, about a fat knuckles worth of clearance with a spacer.
 
#33 ·
If the stud is 14mm in diameter then from the face of the lug nut/start of the threads, to the last thread on the lug nut the distance must be at least 14mm. It doesn't matter if the stud is long enough to protrude 1 thread or 50 threads past the lug nut; the key is that for a 14mm diameter stud, there must be 14mm of thread engagement.Thought of in another way, 4 threads of engagement for the sparkplugs has been shown to be a problem and 8-9 threads of engagement generally solves the problem. Notwithstanding the above, there is no substitute for proper tightening/torquing be it a spark plug or lug nut.Threads protuding from the end of the nut only aid visual inspection whether is is an aircraft or John Deere Combine. Of course you could machine the nuts thinner to achieve thread protrusion, but you may then not meet the standard for thread engagement and if the nut was only engaged with 4-6 mm of threads, perhaps you would be the subject of a Youtube video.
 
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