04 May Adapting Non-VW Wheels
While it was not an easy swap, I feel that it was well worth the effort. I went from “just another black 67 with polished EMPI repros.”, to having a car that is truly my own. I am going to try to review some of the major steps it took to adapt these wheels. I will probably miss a detail or two. Keep in mind, these tips will probably apply to adapting any style or size wheel.
First, let me describe the wheel to those of you who haven’t seen them. The wheels are original Torque-Thrust “D” spokes. They were made in the early 70s for road racing Porsches. The “D” designation refers to the arch in the spoke that allowed extra clearance for disc brake rotors. These wheels are made from Aluminum (also available in magnesium), and measure 15″ x 7″ with 4 ¾ inch backspacing.
I had seen a pair of Americans on the rear of Mark Herbert’s infamous SSB in June at the Classic, so I knew that the 7″ width would work on the rear of a beetle. The major problem was to be fitting them to the front.
To start with, I fitted factory “short” (pre 65) axles to the rear of the car to allow for the bigger wheel. I used a standard 4 lug drum brake on the rear, and had it re-drilled for the Porsche pattern. This is something that can be done by any good machine shop, or you can order new drums already drilled from many parts houses. With the 7″ wheel on the rear with a 215/65 tire there is only about 3/8’ between the tire and the spring plate. I have never had a problem with rubbing, and they fit the fender just right.
At the front of the car however, things get a little more complicated. To start with, I had Dave Pleasant at Quality Machine Co. in Dayton Ohio cut and narrow the wheels down to 5″ width. To do this, he cut 2 inches out of the backside of the rim and heli-arced it back together on both the inside and the outside of the rim for strength. This is an extremely critical operation. If this operation is done improperly, the results would be an out of balance rim or even a broken rim.
Next on the agenda was to narrow the front beam. I am using welded, dropped spindles to lower my front end so this pushes the front track out 1 1/8 inch wider than stock. ( 5/8″ per side) This along with the different offset of the American wheel meant that I would need to narrow the front axle beam 2 ½ inches to make it all fit under the fenders. Since my car is a ball-joint car, I didn’t need to make any body modifications. Narrowing the axle on a link-pin car will be more complicated.
It is very important to sit down and measure everything out before diving in. Different components such as disc brakes or cast spindles may change wheel placement. High quality wheel spacers can be used to space the wheels out slightly if desired. If spacers are to be used, source them from a high-end wheel dealer. Porsche road racers often use spacers to dial in their front and rear track. As long as you use good quality spacers, and don’t go any thicker than approx. ¼” it should be ok.
Another problem I ran into was locating wheel studs. I found that Pep-boys and NAPA retailers had a wide variety of press-in studs in both SAE and Metric sizes. I would recommend that you buy your studs before you have the drums/rotors re-drilled. This way the machinist knows exactly what size holes to drill so that the studs press in securely. It is critical to make sure that your lug nuts don’t bottom out on the drum/rotor before they tighten down on the wheel. Also, there are different metric thread pitches, so make sure that the studs you buy match your lug nut threads.
As mentioned earlier, these tips should help no matter if you are fitting vintage American Racing wheels or the latest 17″ Porsche Cup wheel. Anytime you change anything in the wheel/suspension/braking area of your car it is important to plan thoroughly, measure carefully, and use only the highest quality parts. It may cost more initially, but you can’t put a price on your safety. Also, any welding or fabricating should be left to the professional if you do not have the tools or training to do it properly.
