A Deal on Wheels I couldn't refuse (Mag 500s)

[SPF Required]

So I stumbled upon a great deal on some reproduction Magnum 500s at a car show this past weekend in Lincoln, CA for my '68 300 convertible. They are 15x7s and came off a '69 mustang so I new the bolt pattern was right. The back spacing on these wheels is 4.5". The current wheels on my car are original 15x6, but the FSM does not list the backspace on the stock wheels. I was told the best way to check for potential fitment issues is to just take off a current wheel and install the rim...but admittedly I am being lazy on checking 'the old fashioned way'.

Wanted to check with you guys to see what experience you might have with similar sized wheels (15x7 w/4.5" backspace) on a '68 ... with fender skirts?

Thanks!

Dean

 

[CBODY67]

The "backspacing" spec will not be in any factory publications, as that spec tended to become popular in the '80s. It WILL vary with the rim width, too.

The older spec was "offset" which relates to the centerline of the wheel's total width relates to where the rear of the wheel touches the brake drum/rotor it attaches to. But measuring this spec is not as easy to do as measuring the backspacing of the wheel. ONLY thing is that many measure the rim width and backspacing from can be measured from the inner edge of the rim, rather than the "bead surface" of the rim . . . which can affect the measurement significantly.

The typical backspacing for a factory/repro 15x7 wheel is 4.25". The space between the wheel mounting surface and the outer edge of the wheels tire's bead-contacting surface. Place a straightedge on the outer bead surface (NOT the edge of the flange!), then measure the distance from that bead surface to where the backside of the wheel touches the brake drum/rotor.

As mentioned, the backspacing will vary with the total rim width, whereas the "offset" can remain the same. A "0 offset" wheel of 7" rim width would have a backspacing of 3.5", but many OEM wheels in that width are 4.25" backspacing, from what I've found. A 6" rim would be 3.00" backspacing at "0 offset". It can all be pretty simple, but also can get confusing, too.

My information on the "typical 15x7" wheel came from a Z/28 website with that information on it. Many Chevy wheels had more backspacing per rim width than many Chrysler wheels tended to, by observation. Not sure about Ford-spec wheels, though. Many people still measure rim width to the outside edges of the rim's flange, rather than "between the bead surfaces", so the whole backspacing situation can easily be mis-stated, as a result.

Possibly the best measure of "Mopar Backspacing" for 15x7 wheels would be the '79 LeBaron 15x7 W23-style wheels? Or the more prevalent 15x6.5" '76 Charger SE Rallye wheels? Or any of the "cop car" wheels (15x6.5 of 15x7"? Anybody have any spare wheels they could measure and post pictures of ?

Thanks,
CBODY67

 

[FURYGT]

I have the same size Magnum 500's on my 68 Sport Fury with skirts. Your wheels should fit with plenty of clearance.

 

[Ross Wooldridge]

I ran 14" Ferd Magnum 500s for years with no issues. The Mopar centre caps will bolt right on too.

 

[SPF Required]

A proud papa moment that my 11-year old daughter jumped right in to help me test fit these rims on the '68 300. Even got to teach her the "righty loosy, lefty tighty" on these old Chryslers:

But then reality set in... you know the saying saying of "if it's too good to be true, it probably is"? I think that might be the case with these wheels. It looks like the center hub at the rear drum is just ever so slightly larger that the seating surface on the inside of the wheel...like maybe only 1/16th of an inch wider. I am still holding out hope that there may be a solution to be able to use these wheel, but my mind is blank on where to go with this.

Is it possible that there could be some type of spacer out there that fits between the back side of he wheel and the surface of the hub on the drum? Could I get away with just slipping a washer over each stud that matches the height of the center hub (this level of car knowledge is a bit outside my wheelhouse)?

 

[SPF Required]

should of looked before I leaped...

https://www.amazon.com/gp/product/B01MRIB441/ref=ox_sc_act_title_2?smid=A23ID4AZTDBV78&psc=1

Mr. Gasket Wheel Spacers 2371

but I was going to show off my kid helping me wrench on the car anyway!

 

[FURYGT]

They make wheel spacers just for this type of situation. You DO NOT want to use washers on the wheel studs.

 

[SPF Required]

So the local parts store didn't have the spacers. Hopped on to Amazon, and to my surprise....Same Day Delivery! On my doorstep by 5PM, on a Sunday!!!

Jacked up the car and gave the rims a test fit... I got me some winners here.

These will be headed to the wheel straightener this week (one of the exterior beads is slightly bent). I am going to work with my daughter on reconditioning the black painted sections, then get the existing tires mounted up. Very exiting.

 

[SPF Required]

As the old adage goes “... if the deal is too good to be true, it probably is.” Turns out those great looking Mags wouldn’t clear the front disc calipers.

But there is a silver lining... I was able to sell them quickly to a mustang owner. Back to the drawing board I guess.