So let's set the stage. We are converting a 68 Mustang with manual drum brakes to power disc brakes. We will be utilizing an adapter kit from Steve's Mustang and donor parts from a '94-04 Mustang Cobra. Sven already has written a superb in-depth article on how to do this correctly so I'm not going to replicate it here:
The instructions that come with Steve's kit are clear and straightforward, but I want to expand on a few areas. Let's start with separating the brake drum from the hub. A really important detail to note here is that the brake drums are secured to the hubs by 'swedging' the wheel studs. Basically, after installing the drum over the shoulder of the wheel stud at the factory, a pneumatic tool expands the OD of the wheel stud, effectively locking the brake drum to the hub. You can see the marks left on the wheel stud by the swedging process below.
So why is this important to know? Based on a number of posts I read in various forums, if you try and press these swedged studs out of the hub, in order to separate the drum from the hub, the expanded OD of the shoulder will over-expand the knurled hole in the hub as it passes through the hub flange. If you reinstall an OEM stud back into this enlarged hole, there's the potential it will spin in the hole when it comes time to torque the lugs nuts as there won't be enough material left for the new knurls to get a good 'bite'. I can't confirm this, but given the number of posts on Jeep and Model T forums on this issue, I chose to err on the safe side and remove the drum from the hub per Steve's instructions. And that is to simply place a plate across the top of the outer bearing retainer and press the hub from the drum, rather than the studs from the hub.
But let's say you do want to replace the original studs with new OEM ones. You still need to get past the swedged stud problem. Well a company called Goodson makes the exact tool you are looking for, and here it is. It's a bit pricey, but after reading some of the backyard solutions to the problem that involved all manner of hacking, beating, grinding and overall general mayhem, this seems like the gentleman's solution to the problem.
OK then, let's get back to SusieQ. In my specific case, I actually wanted to save the original studs, so I had no need for the $92.99 tool above. And the reason I wanted to save the original studs was due to my wheel choice. As you recall, I'm going to run 2005 Mustang GT 17" rims. In order to do that, I need to run ( yep, you know it's coming) 1" wheel spacers. I feel as much shame about it as you do. But I love the rims and they are exactly the look I want for the car. Yes, I know, I should just run a rim with the correct offset and do the job right. In my defense, all projects are ultimately a series of compromises - this is mine.
And this is where 'the devil is in the details' raises its ugly head. Since Cobra rotors are used with a shoulderless wheel stud, they will not fit over an original OEM shouldered, brake drum stud. Worse, they really won't fit over a swedged, shouldered, brake drum stud. The stud holes in my OEM Cobra rotors were roughly .570" ID. An unswedged stud shoulder measures .605" OD, a swedged one almost .617". So it is a no-go by quite a bit. When I first discovered this problem, I thought I would be clever and just order a new set of OEM shouldered studs that hadn't been swedged - only to discover that even the un-swedged ones have too large an OD. As a heads-up here, Steve does sell a wheel stud just for this issue (#610-368). They are non-shouldered, longer for the thicker flanges of modern rims and even have a larger OD knurled section for pressing into hub flanges that have had previously installed studs. Only thing is, I can't use them. The longer length causes them to protrude out past the outer surface of the wheel spacer. This would prevent the rim from sitting flush against the mating surface of the spacer. Fudge...
|OEM brake drum wheel stud - C3AZ-1107-A (1 11/16"L)|
|Steve's Mustang - shoulderless wheel stud (2 3/16"L)|
|13" Cobra rotor in the mill w/ 5/8" ream|
|rotor chucked in lathe - plugged to keep shavings out|
|close-up of turned diameter and 45 deg, 1/16"wide chamfer|
In Part 3 we'll finish up with some polishing and powder coating. Stay tuned!