Lug Bolts often are incorrectly called “nuts”. For the 1967 Beetles these bolts are 12mm X 1.50 thread with a 9mm head.
Over-tightening the lug bolts not uncommonly results in stripped drum threads. Or, perhaps it is just the years of loosening and retightening the steel bolts that eventually wears the soft cast iron threads.
Once the threads in a drum hole have been stripped, the car should not be driven. The lack of one lug bolt can bring about failure of the remaining bolts due to the undue stress placed upon them.
An obvious solution is to buy a new drum. But, as with many other Volkswagen Beetle situations, there is a good solution which will save that drum!
But, first, let’s talk about some tools which will make this job possible. If you don’t own the tools which we will discuss, or don’t want to own them, you may be able to find a shop or VW friend to do this repair for you. My VW friends and I have found it difficult to locate a shop with the proper tools to do this job.
An alternate idea would be to purchase the tools, then to take the drum and the tools to a qualified machinist to have the work done.
You will need the following:
- 1. Drill Bit—31/64th inch
- 2. Tap—14mm X 1.50 Thread. Use the taper or plug (or “spiral”) tap
- 3. Die—14mm X 1.50 Thread
- 4. Lug Bolt from a 1968 and later Beetle, Type 3 or Karmann Ghia (USA specs)
- 5. Tap and Die Kit with the proper tools for using the Tap and the Die
- 6. Heavy duty battery-powered or electric 3/8ths inch Drill Motor or a Drill Press
- 7. Light oil or some other drilling-aid fluid—even WD-40
- 8. Torque Wrench
Compare the 12mm lug bolt and the 14mm lug bolt—both in diameter and in length.
Remove the offending brake drum. Time to do a little cleaning of it, anyway. Maybe even to paint the outside so that it will resist rust better. The cast iron holds paint well. If you were in a hurry, you COULD do this job leaving the drum on the axle. This is not advisable since it leaves metal shavings in there with the brake shoes.
First you will need to drill the stripped hole to the next size. Wanting to leave as much “meat” as possible for the new threads, we are going to use a 31/64th bit. A ½ inch bit will work but will remove too much metal and can result in weak threads when the hole is tapped.
Drill the hole cleanly. Usually it is easy to hold the drill motor straight while drilling, but be as careful as possible to get a good, straight hole. If you have a drill press, this process will be easier.
Now, for the 14mm X 1.50 tap. Install the tap into the proper handle from your tap and die kit. Again, taking care to hold the tap straight, tap the new threads into the hole. You can use a light oil, or even WD-40, to help the process.
Clean the new threads well using compressed air, if you have it. If not, a small toothbrush or other device will work. Computer-cleaner canned air will work.
Use a wire wheel or some other cleaning device to thoroughly clean the threads of the 14mm lug bolt which you have selected as the replacement bolt. Rusted bolts will not torque smoothly.
Lay the wheel over the drum and install the 14mm bolt into the newly threaded hole. The bolt may protrude through the drum a bit. If so, this protrusion should be removed so that it will not bear upon any of the braking mechanism as the drum turns.
A bench grinder works well to shorten the bolt, but a hacksaw also will work. Secure the bolt head in a vise and cut to remove the tip of the bolt.
Once the excess has been removed, I like to run a die over the threads so that they will be straight. If no die is handy, use a small file to straighten the threads at the tip so that the bolt will turn into the hole smoothly.
Once you are satisfied with the bolt length, reinstall the drum onto the axle.
In the USA, the 1968 and onward, Beetles, Karmann Ghias and Type 3s have the 9mm head just as do those of the 12mm bolts for the “wide-five” drums. As a quick way to recognize the larger diameter bolt and hole, use a spot of paint or fingernail polish to mark the bolt and the hole.
With the car still on a jack stand, position the wheel and screw all 5 bolts in by hand until the beveled shoulders have seated. I use a socket at that point to tighten all of the bolts, going diagonally from bolt to bolt. Tighten until all are well secured but not yet torqued, due to being off the ground.
Now, we come to avoidance. Torque the 12mm lug bolts properly. Don’t use a big wrench or socket bar and stand on it! Use care and likely you won’t have a repeat performance. Lug bolts for the “wide-fives” (5-lug) ’67 rims should be hand-torqued to 72 ft/lbs. (14mm X 1.50 bolts should be torqued to 87-94 ft/lbs). The paint-dot will help you to remember which is the 14mm bolt.
Lower the wheel onto the ground and torque the bolts, going diagonally from one bolt to the other until all are properly torqued. Maybe you have a more modern torque wrench than mine!
And, there you have it—one salvaged 5-lug drum. Plus, you have a kit for the next stripped thread situation. If you have a close-knit VW club or group, maybe you have communal tools. In my case, I lend this tool kit to my VW friends so that they won’t have to purchase the set themselves.
I buy used lug bolts at swap meets anytime I see them. I find them to be handy for situations where I am working with a car that is missing one or more. Carry a couple of each size with you in the corner of your road tool kit and you’ll be thanking yourself when you’re down the road. Your VW friends will be thanking you too…when they become stranded and find that you have just what they need to get going again.
Special Mention: I want to thank fellow-Texan James Anderson for starting me on this journey. Presently, James is working to complete the restoration of a black 1967 Beetle.