wheel stud length

[dmc69]

I have a 69 camaro and I am uprgrading my rear drums to disk using the baer 12' rotor setup. Everyone is suggesting upgrading my studs while I have the axels out. I am running boze tach wheels, 18/10 on the rear. What length studs should i use?

[John Wright]

Are they saying to upgrade to a longer stud? or a larger diameter stud?...or stronger grade of stud?(ie ARP)

The stud needs to be long enough for proper thread engagement with the nut, unless a sactioning body asks that the stud protrude "x" past the nut for safety inspections.

[dmc69]

stronger grade arp 1/2-20, but im not sure if its the 2.5 or 3.25

[gort69]

Most rear rotors I've looked at are ~ 1/4" thick at the hub. The original drum is ~ 1/8" thick. In order to get back to the same thread engagement you have now, a stud 1/8" longer would do the trick. But measure yours, don't take my word for it! Rotor thickness minus drum thickness.

And make sure you have enough thread engagement with your current set-up. A rule of thumb that I have heard is that the thread engagement should be equal to or greater than the diameter of the stud. So, assuming a 7/16-20 stud, I'd shoot for at least 10 full turns of the lugnut before it tightens up.

[JRouche]

stronger grade arp 1/2-20, but im not sure if its the 2.5 or 3.25

While you have the axles out it makes sense to replace the studs. Thats prolly what some folks have said. But.. If you are not making some dramatic changes to your HP and torque (BIG engine, 1000+ torque with big tires) then the wheel studs that have been in place for many years will continue to serve well. Unless they are buggered up, the threads. Which you dont see much because wheel studs are pretty tough and the way they are cut makes it so a mom on the side of the road can change her own tire. Wheel studs are some of the highest designed components on the car. They are meant to allow ANYONE to thread the nut on in the worst conditions. Ever hear of a wheel stud getting cross threaded? I havent. They are fool proof. They are one of the few fasteners that are meant to be re-fastened over and over, again and again over time. Think about it. Not many fasteners on the car are designed to take that abuse.

But from my thinking the studs have been torqued many times over their life span. A fastener is like a spring in a way. It takes a stretch for every cycle. And a wheel bolt is not like a rod bolt. The rod bolt of the engine is in a constant cycle of extension and relief.

Where a wheel stud is in constant extension, a tension load that is constant. No cycling of loads. So they will survive for a very long time.

But studs that were in place from the 60s may have seen some abusive torquing cycles as the years went by. If it saw alot of tire shops that used an air wrench to cinch the nut down, and the guy on the wrench was overly enthusiastic then the stud could have been overly stressed. Kinda funny to be able to see what a car went trough for its entire life.

So yeah, I say toss some new studs in there while you can. And I dont think you need ARP studs. Many supplies can give you some more 40 year studs. ARP produces some top of the line fasteners. I dont think wheel studs from them are needed for a majority of the cars. Any of the axle manufactures and rearend dealers will have some less expensive studs that will out last you, me and the car. JR