Threads

[Jnikic]

I've heard lots of different opinions on what the minimum threshold for a safely engaged wheel nut consists of, but I'd like to hear more ...

I'm trying to fit a new set of rear wheels with a massive 335 section Hoosier on my track/race 911, but they require 25mm spacers - leaving 10 complete turns of thread engagement on the steel wheel nuts. But that's only about 1/2 of the nut itself.

Would you run it? In the near short term I will change the wheel stud length, but don't have the time before next weekend.

What say you?




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[proffighter]

Sounds like a bit weak to me. General rule is 1.5 x diameter gives max possible for a thread, more does nothing (on equal material of both) If in your case the 10 turns are 1.5 of the diameter, you'll be fine

[Jnikic]

1.5x the diameter of the nut?

I'm not sure the height is even equal to the diameter (i.e the height of the nut is smaller than it is across or at the least, they're equal)


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[ClickClickBoom]

Aircraft world, minimum one thread exposed. Lots of dynamic forces on wheel studs, really wanna take a chance with minimum engagement? Imagine the consequences of the wheel coming off in a 3rd gear, full throttle sweeper at redline, then ask if you want to try it on for size....

[wayner]

Are you planning a track event ?

Many organizations require three extra threads showing

[proffighter]

Bolt diameter.

Example:

For a M14x1.5 it's 21mm which reaches max. strength. Less is weaker, more does not add more

[Cattler]

This seems to be pretty standard from the PCA rule book, AX guidance, etc.:

Wheel nut or bolt must fully engage the threads on the stud or hub for a length at least equal to the outside diameter of the wheel stud or bolt. The use of open-ended steel lug nuts is required in all cars with 400 or more Performance Equipment Points where lug nuts and wheel studs are fitted. The use of open-ended steel lug nuts is additionally required on all cars using lug nuts that have non-stock wheel spacers fitted, to allow verification of compliance with this section. Wheels must be torque to specification.

Best,
Dave

[JJ 911SC]

Originally Posted by ClickClickBoom

Aircraft world, minimum one thread exposed....

In the Navy too...

Quote (Naval Ships' Technical Manual)
075-7.5 LENGTH OF THREAD PROTRUSION

075-7.5.1 MINIMUM THREAD PROTRUSION.

A minimum thread protrusion length is given to ensure that
all the threads are engaged. This is required to ensure a full-strength fastener. Equipment component drawings
should specify the type, length, and size of bolt, stud, bolt-stud, etc. to be used to obtain the proper thread protrusion.
If not specified on the drawings, threaded fasteners of commercially stocked lengths should be used.
Threaded fasteners, when installed and tightened, should protrude a distance of at least one thread beyond the top
of the nut or plastic insert. Excessive protrusion should be avoided, particularly when necessary clearances,
accessibility, and safety are important. Thread protrusion is considered excessive if it could cause damage to
machinery or harm to personnel. Where practicable, the number of threads protruding should not exceed five. In
no case should thread protrusion exceed ten threads. In the case of a stud, excessive thread protrusion may indicate
that the stud has not been properly driven in the blind hole. In self-locking nuts where the distance from the
top of the nut to the locking element (plastic insert) is equal to or greater than the chamfer, the bolt or stud end
may be flush with the top of the nut. For existing or reused fasteners where the thread protrusion exceeds 10
threads, verification should be made that the proper length fastener was installed. For existing installations utilizing
standard nuts, acceptable minimum thread protrusion would be where the male thread, below any
unthreaded chamfer or crown, is flush with the top of the nut. Washers should not be added to reduce protrusion
except as specifically required by equipment component drawings or technical manuals.

[Jnikic]

Thanks gentlemen

[JJ 911SC]

Originally Posted by proffighter

Bolt diameter.

Example:

For a M14x1.5 it's 21mm which reaches max. strength. Less is weaker, more does not add more

Correct, we use the 1.5 rule for fastener on First Level systems on submarine, could be over kill on wheel with 5 studs but better be safe then sorry.

For the record, while I apply the above on my day job, my front rims are about 1 thread short of being flush and I'm not loosing any sleep over it.

[cgarr]

I would not run it like that:

[proffighter]

This rule with one turn over the flush is just to see, if one is loose and at lock nuts of course to be "clamped" for sure.