[Rick Parker]

The problem that is unappearant to the novice is that the pin drives on the original cars both 289 FIA/427 was a 6 pin on a 4 1/4" bolt circle. The pins themselves have a 3/8" diameter threaded portion that provides the locating and clamping forces to hold the center Spud or hat to the drive flange. The drive portion of the pin is 1/2" and inserts into the wheel itself. The Trigo adapter attempts to minimize required macine work by utilizing the existing studs in the axle flange (normally 1/2") and bolt circle 4 1/2" (Ford). The barrel nuts are 3/4" diameter cylindrical about 1 1/4" long with a tapered face on one end and internal wrenching hex on the other. They screw onto the studs in much the same design clamp the threaded hat to the axle flange and combine with the studs to form the drive pins that are 3/4" diameter in this conversion. In my application I had to change to 6 studs/pins as the 5 stud/pin pattern could not be made to fit on the back of the FIA style wheels that were part of my project. The mounting pad on the back of the wheels have a scalloped unusually shaped pad which will not allow for a 5 pin pattern without reducing the bolt circle diameter significantly (weaker). I could have used the original 3/8"-1/2 drive pins (relocate hole centers) but I was concerned (overly??) about the power being driven through the 3/8" threaded portion of the original studs, it goes against everything I read about fasteners and mounting them in shear. I considered having special drive pins made (longer threaded with a shoulder area) but at $500+ for 26 (2 spares) I considered against it. What I have is consideably stronger and capable of handling more horsepower and abuse than the original design and has (6) - 1/2" studs in shear with the power driven through pressed in studs bearing on the splined area insted of the power being driven through 6 - 3/8" (threaded area) pins. If these pins break you will lose a wheel. I'm sure that the 5 pin fitament is plenty strong given the fact that most domestic vehicles including 1/2 ton pickups until recently utilized only 5 studs to mount their wheels.

Hope this helps!!!

Rick