1965 GT350R original magnesium wheel exact dimensions?

[SeanSide]

Hi,

I have been trying to find an answer to my question. I am trying to find the exact dimensions of the original magnesium wheels on the 1965 gt350r. I found contradicting information on other forums and need clarification, especially on the backspacing:

American racing TTD: 15x7x3.75BS

PS engineering trans am: 15x7x4.25BS or 4.5BS
(read somewhere that 15x8 were maybe used on the rear for the 7.00-15 tires)

Vintage engineering: 15x7x3.75BS
(magnesium wheel replica)

Just got an email reply today from Ray Franklin of Vintage Engineering who used to make replica wheels, this is what he said:
– We did in magnesium. Out of stock. We no longer make these due to retirement and the tooling is for sale. Our wheels were modeled after an original wheel and has a 3.75" backspace.
Ray, Vintage Engineering

Wonder if anyone has the definitive answer.

Thank you, Shawn.

[98SVT - was 06GT]

The 65 was homologated and raced with the 7" w/3.75 BS. These were off the shelf American magnesium wheels. There were no other wheels as options. Shelby was all ready to get Donahue DQed at the finals if he had won. This was due to his 8" rear wheels and larger Firestone tires. The tires rubbed the sidewall on the rear spring during the race caused a failure.
Jim Wallace came up with a backspacing dimension (at least here in SoCal c.1975) that allowed the 8" to run on early cars with only rolling the lip (flare stayed stock externally). These are the numbers Phil was using on his wheels (unless you spec a different #).

Here is the 68 FIA homologation for Group 2 wheels - none of them spell out the BS - you'd need to dig into the archives for the full description (blueprint?) for actual BS by part number:
MAKE: Ford MODEL:1968 Mustang 302 FIA
S7MR-1007-II/J 15" x 8"
Optional Wheels
C7ZZ-1007-D 15" x 6"
S7MR-1007-M/N 15" x 9"
S8MR-1007-A/B 15" x 10"

[SFM5S000]

Shawn,

I had an in-depth conversation with Phil Schmidt before I ordered a set of 5 (4+1 spare) of his PSE 1 piece Trans Am wheels in 15x8. Phil's recommendation was with a 4 3/8" back spacing as that's what he was running on his 65 GT350 SFM5020.
Unfortunately Phil Schmidt Engineering is no longer as are his wheels. I was going to point you to Vintage Engineering in Redwood City CA, but you found him already.
I'm running the PSE 15x8 with a 4 3/8" back spacing. Just the tops of my fenders have been rolled. I've run and fitted 600-15's in the front and 700-15's rears in the past. On the street now I run 225x60-15 (f) and 235x60-15 (r). I can squeeze in 245x60-15 rears just fine and will go that route on the next round of tires.
On my PSE rims my only special request was the fill valve holes, I requested them on the drop walls and not in between the spokes. This is what it looks like.

Cheers
~Earl J

[98SVT - was 06GT]

The 4 3/8 BS on an 8" wheel is critical to getting it under an early car. If you are going to use the original size 7" wheel 3.75 will work just fine. The D designation on the wheel was the altered spoke shape that allowed clearance for the disc brake caliper.

[SeanSide]

The knowledge on this forum never ceases to amaze me. Thanks a lot for the clarification, all makes sense now!

Those PSengineering wheels really give an amazing look Earl 👌🏻

Meanwhile Vintage Engineering gave me details about his tooling for sale in case someone is interested, here is his reply:
-    The tooling is 4000$.
This tooling creates the sand molds that the magnesium pours into.
From there you need to machine the rough casting to finished dimensions
Machinery is not included. Depending on where you live. Finding a shop to machine is not difficult. Ray

[kram350]

I can confirm that the original Ameriacn magnesiums are 15"x7" with 3.75" BS. Have been racing them for  40 years with 600-15 Goodyears. Just be aware 600-15 tires will still slightly rub on the rear springs and rear fender lips when you really push, even with a panard rod. On the fronts not much of an issue, but be carful backing up with the wheels at full lock.   

[98SVT - was 06GT]

Meanwhile Vintage Engineering gave me details about his tooling for sale in case someone is interested, here is his reply:
-    The tooling is 4000$.

Since Covid casting prices have really jumped about a 60% increase. If you did 100 wheels (25 sets) you'd have $40 in tooling Probably $50 in machine work $20 in aluminum - $110 before you pay for the casting work $75(?). At $200 each you might make a little off a 20 grand investment. You'd probably add 20% to the material and casting costs if you used magnesium.  https://www.custompartnet.com/estimate/sand-casting-std/

[TA Coupe]

Earl and I both like the PSE wheels only mine are 17x9.5 and 17x12 and they are on a 1970.

     Roy