Thread: min. stud length

Tweet

I just got my wheels and they have some pretty thick flanges.
Also turns out I may need a 1/4" spacer, which really eats up
stud length. My studs are only 1 1/8" out from the drum surface.
With those wheels on it can't be more than 1/2", and that's with
NO spacer.

Do you guys think I need to pull these axles out and put in longer studs?
Are there any publications I could find the failure load for bolts as a function of thread engagement?

There's a reason most tech inspections insist on open-ended wheel nuts with some threads coming past the nut. With closed end nuts, its important to measure everything and be sure the studs go most of the way to the end of the wheelnut threads. One trick is to try an open end nut, and see if threads poke out, then the studs are long enough.

I think I may just have to replace the studs. Hopefully I can get them in and out without pulling the axles on that ford rear.

Also, it turns out I have my rear 1/4" off center so I only need
the spacer on one side.
Is that going to significantly affect the handling?

A thread engagement length equal to the diameter of the stud is what you're looking for, at a minimum. For instance, 7/16" stud, minimum 7/16" thread engagement.

Here's an explanation I wrote in another post....

When cars are built at the factory, studs of the proper length to project out beyond the wheel surface and engage the lug nuts are installed, whether the vehicle is fitted with conventional steel wheels or factory mags. Our problem arises when a steel wheel (which is very thin) is replaced with a much thicker-section aftermarket mag wheel. Now, the stud is back inside the wheel and does not project beyond the wheel surface. The aftermarket manufacturers addressed that by manufacturing "tube-type" nuts with a long cylinder that fits back into the stud hole. The cylinder is threaded in its I.D. so that the thin cylinder engages the stud and the wheel is held on by the shoulder of the tube-hex nut junction. There are a couple of problems with this design from a drag race standpoint. First, the stud does not project into the hex portion of the nut as required by the rule. Secondly, the tube/nut arrangement has a tendency to break at the tube/nut junction and with nothing now holding the wheel on, the wheel and tire passes you in the other lane. Now you're probably thinking, well if I simply install longer studs, I'm covered! BZZZZZT. Wrong. Problem is, most of the tube-type nuts are NOT threaded in the hex portion of the nut. Some are, but most are not. Your new, longer studs could be engaging AIR. Even with longer studs, the nut can still break at the tube/nut junction and zowie, there goes your tire and wheel (and maybe also your new shiny paint job and that NOS fender it took you 6 months to find). Again, the savvy racers have it figured out. They install longer studs and open-ended nuts so the tech inspector can see at a glance that the stud engages the hex portion of the nut by at least the diameter of the stud. They usually leave a couple of threads of the stud stickin' out past the end of the nut and it looks real nice. Just as nice or nicer than blind nuts in my opinion. Of course, I may be looking at it with a jaundiced eye because I have a real appreciatation for good, safe engineering. We keep a 4-way lug wrench at tech and the driver must remove at least 1 nut from each wheel if using "blind" nuts so we can verify that there are threads in the hex portion of the nut and that the stud engages the threads by a length at least equal to the diameter of the stud. The racers who show up all the time got tired of this routine, so they just installed open-ended nuts so they won't have to pull nuts each time they show up. All the rule is saying is that if you have 7/16" studs, then the stud needs to engage the hex, threaded portion of the nut by a length of at least 7/16". If the stud is 1/2" diameter, the stud needs to engage the hex, threaded portion of the nut by a length of at least 1/2".

The car will never know that one wheel is spaced 1/4" different than the other.

cool, thanks for the info.

I'll be changing those studs.

yes my cars have open end nuts i like the looks to. they are safer some of the better. nuts .tube type some are made better with bar stock . some are stamp and no threads thru the nut part this type are junk like tech said

There's nothing intrinsically wrong with tube-type nuts, every semi on the road with Budd wheels uses them. The thing is to get wheels, studs, and nuts that work together.

I just got my lugs and it turns out they are the open type.
The picture online showed the other type.

Also turns out I need a tool for them that I don't have.
figures.