[DeTomaso] Wheel Weight

[Thomas Borcich]

I use to watch the three piece wheels being made back in the 80's by a very well known racing wheel manufacturer who 
I think is still in business today (I won't mention the name). These wheels were the number one wheel used in the 
Formula Atlantic Series at the time. I saw quite a few of those wheels used on street cars, Porshes, Ferrari's, etc. 
I think many forget that there is a huge difference in weight of a Formula Atlantic car (1,000-1,500 lbs+/-)  or similar race car 
vs. a street Porsche, Ferrari, or Pantera (2800-3500 lbs) and the related stress due to that weight. Also, throw in pot holes, 
curbs, and other assorted road hazards which aren't present on most race tracks, or bolt that wheel on and add a four to 
eight inch wider gumball tire to pretty much the same wheel manufacturing process and materials bolted to a Pantera and 
you have may have quadrupled the stresses on that wheel? Sorry I'm not an engineer so I haven't done any 
stress calculations, I'll leave that to someone on the forum. 
 

The centers were a cast piece that was later machined down into a finished piece by an outside vendor. Those centers may have

been forged, don't recall. I was quite surprised to see how crudely the wheel halve/hoop that bolts to the centers were made. 
The actual rim halve that is bolted to the centers was made out of flat sheets of aluminum about an eighth inch thick, bolted to a 
form/buck on a lathe shaped like an inverted bowl. The tool to form that flat piece of aluminum over the buck, was a five to six foot 
long bar with a forming wheel pressing against the flat piece of aluminum and moved along the base of the lathe. 
The guy doing the forming and manipulating of that bar was 6'6" tall and over 250 pounds, pulling on that lever with all he had,
forcing the metal to bend and form to that inverted bowl shape on the lathe!!! I tried to do it and barely moved the metal. Multiple 
passes had to be made over and over to get the right shape against the buck. That's not very scientific in my book and susceptible to 
human error. Given the amount of forming done to make the hoop the metal has to be pretty soft to not crack or break during the process.
I don't recall if the wheel hoops were later sent out for heat treating?

After seeing how they were made it doesn't surprise me that there were
lots of failures. I don't think there were ever any back of envelope 

stress calcs done considering the manufacturing process. Worse, the lathe operator could have put a little too much pressure in one spot 

when forming a bend in the hoop which made that cross section of the
wheel thinner and more suseptible to cracking......I saw wheels come 

back for repair for various reasons, cracks, crashes and leaks...a new
wheel halve was supplied and bolted to that center and off they went.


I just went out to my garage and looked at the wheel hoops on my Codington
clones waiting to go on the Pantera...they have similar rotational 
forming marks on the pressurized/tire side of the wheel as the racing wheels I mentioned above...so maybe the
process hasn't changed significantly, although
 I would think that the process is far more mechanized and there is more quality control on a DOT approved wheel.  When I was at Codington's
warehouse picking up my wheels, there were wheels stacked 15-20 feet high, covering a football field so either they are very well insured or 
the process is much better, I hope it's the latter.

  
Tom