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9/16 wheel studs upgrade

kontradictions

kontradictions

1/2 ton status
Joined
Jul 14, 2006
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Southern California
im converting my 7/16 wheel studs on my 10 bolt and got a set of 9/16 wheel studs and lugs for the job.

The knrul diameter on the 9/16 studs is .620"

I was wondering what I should be drilling the hole out to for the larger studs on the hubs and rotors. After doing some searching I found some people saying to drill it out 1/8 to 1/16 smaller than the knrul size on the studs for a good press fit.

By those measurements i should be drilling it out to a 0.495"-0.5575"

I just pulled the hub off and punched one of the studs out and my 1/2 drill bit was to small and just past right through the hole without touching. Obviously I need to get a larger drill bit to bore this out some, but I didnt know what size would be best.

I was looking at a 17/32 (0.5312") or a 35/64 (0.5469").

If anyone has any input on this I would appreciate some guidance so I can get this done.:D
 
ok well after doing some more research, the moroso site is stating all wheel hole sizing needs to be between .001" to .008" smaller for a good press fit.

That would mean i would need a drill bit around a 39/64 (0.6094"), making the whole size about 0.0106" smaller and about the closest to that range i can find for a drill bit.
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One thing to note is that the size of the drill bit does not exactly match the size of the hole it drills (unless you have a milling machine and super nice bits). The holes tend to end up being a little larger than the bit.

I'd go a little smaller than you need and check it afterwards with some calipers.
 
im aware of this and even with a larger hole the tolerance i am allowing is still going to be within the margins.

I have already drilled and pressed in the new studs and everything is great. Very simple to do, took about an hour for both sides.
 
kontradictions said:
im aware of this and even with a larger hole the tolerance i am allowing is still going to be within the margins.

I have already drilled and pressed in the new studs and everything is great. Very simple to do, took about an hour for both sides.
Click to expand...

Hijack on where in socal do you live? I saw a K5 that looks identical to yours at a carwash in Linda Vista on Saturday. Could that have been you?

Dick
 
sandawgk5 said:
Hijack on where in socal do you live? I saw a K5 that looks identical to yours at a carwash in Linda Vista on Saturday. Could that have been you?

Dick
Click to expand...

Im in south orange county, so it couldnt of been me. I was at work all day anyway with the blazer in costa mesa.
 
kontradictions said:
Im in south orange county, so it couldnt of been me. I was at work all day anyway with the blazer in costa mesa.
Click to expand...

:doah: Oh well.

I have noticed quite a few mor C/Ks around San Diego lately

Dick
 
39/64

I ended up getting it from McMaster-Carr, luckily they are right by me so i am able to just go over there and pick it up just like going to home depot!
 
Thank you for this information. I determined a while back that nobody makes a "drop-in" 9/16 stud for the front. I never went further to figure this mod out. Do you know the original application for the stud you used or have a part number?
 
kontradictions said:
im aware of this and even with a larger hole the tolerance i am allowing is still going to be within the margins.

I have already drilled and pressed in the new studs and everything is great. Very simple to do, took about an hour for both sides.
Click to expand...

Hi I'm about to do that same job on my 85 k5 blazer can u help me what size still bit did u use and do u have any helpful tips thank u
 
Just completed 7/16 to 14mm stud conversion on 86' k5 blazer with gm 1/2 ton 6 bolt axles. Drill front and rear with 39/64 bit. Rear axle gets Dorman 610-328 aka Napa solutions 6412172 studs. Front gets Dorman 610-615 aka Napa solutions 82002251 studs. Front stud knurling will engage the rotor with shoulder fitting hub loosely about .004 or 4 thousandths. A few drops of loctite on shoulders will eliminate this tolerance of so desired.
 
As far as I can tell, neither of the studs mentioned is designed like OEM, meaning the knurl isn't biting into what GM intended it to bite into.

I'm not an engineer, problem, or not?

I spent a ton of time looking for a larger front wheel stud for a 6 lug front, I found exactly one (1/2") that was designed like the OEM 7/16" stud. I figured GM had a reason to have the lug bite into the hub and not the rotor.
 
The rear stud is a factor rear Gm stud found on all 90ish+ half ton drum brake axles. As far as the front, the purpose of knurling is to keep the stud from turning. A regular bolt with the appropriate shank length and diameter would be more than sufficient assuming you could put a wrench on the head. For more of a press fit, the hub could be drilled to 19/32 giving a .012 interference fit. If you are interested in custom fabrication, 1970's engineering intent is of very little consequence.
 
40acrefarmer said:
As far as the front, the purpose of knurling is to keep the stud from turning. ...1970's engineering intent is of very little consequence.
Click to expand...

I get what knurling is for. GM likely could have saved millions using a much more common stud design, which was already regularly in use at the time. Custom fab or not, I am trying to understand what benefit having the stud bite into the rotor would have.

With the amount of torque the little studs are spec'd at, larger studs based on torque alone are obviously going to perform better than OEM.
 
I reviewed the specs on every 1/2", 7/16", and 14mm studs Dorman makes. Made a list of every stud that could work on front and rear. 14mm was the best compromise. Ideal stud lengths, same drill bit size, and good shoulder length on front stud. Knurl bitting into rotor was also a compromise. Not saying it is superior to oem or ideal. Intent of my post was to let others know that this setup will work, will work well, and hopefully save someone a day of reviewing hundreds of studs and specs.
 
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