Rear Wheel and Tire Installation - 1967 Chevelle
Hi. Remember me? The wheel weirdo. I’m back and this time I want to cover how I figured out just how much I could get away with on the Chevelle.
This car was originally a street machine that was completed in the mid-eighties. The warmed-over 283 backed by a 3500 stall in a TH350 and a 3.90 posi was really a pretty potent combination. I came to learn after a little more digging, that the rear end in the car had actually been swapped in. The casting numbers linked it to 64-67 BOP (Buick, Olds, Pontiac). It was a factory posi-traction, 8.2” 10-bolt with GM 3.90:1 gears in it. A sought after piece for those restoring GS, Wildcat, Cutlass or GTO back to numbers matching. Ultimately, that’s where the full rear differential from the car went. I sold it to a friend who is a hoarder of everything 60’s Buick. We agreed on a price that would further fund the bastardization of my (formerly) almost numbers matching Malibu.
If you’re going to commit sacrilege, you might as well jump in knee deep. If you’ve been following the series, you already know that I opted to go with a 9” Ford rearend over the “correct” GM 12 bolt differential. I just couldn’t justify to expense of locating, narrowing and building a 12 bolt. The Ford rear has the added benefit of a drop-out center which will also allow me to experiment with different gear ratios.
Since my primary role at Speedway is to create, source and select new product, I wanted to also end up with a working, marketable product from the end result. The original axle in a 64-67 A-Body measures 62” across the wheel mounting surfaces. As I measured and mocked up parts with the stock housing in place I determined that I could conceivably shed an 1” from each side. This would bring the wheel, tire and brake arrangement right up to the lower shock mount. I used a Percy’s Wheelrite to triple check my hypothesis. What I found, was that I could fit a 10” wide wheel with between 3.75” and 4.5” of backspacing, depending on how much tire I wanted to run. With clearance enough for brakes, coilovers and even 15” diameter wheels. Which was exactly what I wanted to know.
From there, I bought just one 15”x10” wheel to test fit on both the factory width housing and eventually, when the prototype was finished, the narrowed 9” housing. Lucky for you, you don’t have to wait several weeks for the new housing. Long story short, a deep 10” wheel won’t work on a factory 62” rear without hanging out. Not what I’m going for on this car. However, on a 2” narrowed housing, they fit like a glove.
I chose Wheel Vintiques O.E. steel wheels in 15”x10” and 15”x5”. These are standard, off the shelf wheels. One of the things that I try to consider any time we’re working on new chassis and suspension parts. I don’t want a customer to get a great deal on parts, install them and end up finding out they have to buy $4,000 in custom made oddball offsets.
With the new housing and brakes installed in the car, my mockup really started to take shape. As I experimented with different tire sizes, I found that I could easily fit a 275/60 or 255/70 tire in the fender well, all the way to the top of the wheel house. I found the limit with a Firestone Indy tire. It was a 1200-15 size. For reference, this is the same size tire as the rears on a GT-40. A 13” wide section width (sidewall bulge) was a bit too much at the fender lip.
So I rolled the lips on the quarters. Did I mention that this was definitely NO restoration project? (As it turns out, this step needed to be repeated again when the car got full quarters later.)
Even though the largest tire I could get my hands on didn’t fit, I still learned a ton about what the possibilities were. As I was to find out much later, I was actually missing out on some tire space due to the “coke bottle” flare in the center of the quarters flattening quite a lot through the process of patching and the way they’d been worked in the distant past from collision damage repairs. But that’s a story for another day.