wheel alignment specs

[dgs]

Controlling a bias-ply tire with all its squirm and only 32-PSI is truly a challenge. One way to help control this squirm is to actually produce squirm equally on both sides by using excessive toe-in. This is exactly what engineers did, at the expense of more tire wear. Back in the day, if we got 15,000 miles out of a tire, that was HUGE.

There used to be a wonderful magazine named Invention and Technology. Back in their spring of 2001 issue (available online here) they did a very nice article on the uphill battle for bringing radials into the US. It was a battle, because when you put a radial on a car tuned for bias ply tires, it drove and rode terribly. The auto engineers, understandably, didn't see a reason to switch.

It turns out, the inherit flaws in the bias ply tire meant that engineers had been aligning their cars, as you said, with excessive toe-in to counter the imprecise handling of the bias ply tire. For a radial, however, that toe-in actually produced a large on center dead zone in the steering, and therefore a lot of wandering at speed. Take out the toe-in, things improved dramatically. That's why many cars had "Radial Tuned Suspension" back in the early 70s. It wasn't just marketing mist.

It also mentioned changes in suspension and driveshaft bushings to reduce the higher noise and vibration levels that came with radials, which we can't really take advantage of. But at least we can align our cars more appropriately for radials.

It's a fascinating article, worth your time if you love to learn the history of technology's adoption. I&T was a fantastic magazine and I still miss it after 7 years out of print. It looks like the entire publication run is available online now, if you need a way to kill some time.

[simplyconnected]

Doug, yes I can appreciate a great article about the radial tires. Now, let's look at the numbers. Our Tire Room can hardly keep up with the Final Assembly Line because:

We make a car/min. Let's take round conservative numbers. That's 60 cars X 8 hrs or (480) cars per shift Let's call it 450.
So, 5 tires mounted, inflated and balanced on wheels w/stems times 450 = 2,250 tires per shift.

Most assembly plants run two shifts so, 4,500 tires per day per assembly plant.

Ford has 20 assembly plants so 20 X 4,500 =90,000 tires per day for Ford. That's ninety THOUSAND tires per day.

Chevrolet is as big as Ford and the rest of GM is as big as Chevy. So, another 90,000 for Chevy and another 90,000 for the rest of GM. I won't go farther with Chysler/Jeep, etc. I"m well over 270,000 tires per day for the industry with NO regard for replacement tires.

For many years, all these tire companies are baking bias-ply tires in molds, as fast as they can. Then, someone comes along with better but higher priced tires. Right...

Are American tire companies are going to take this sitting down? We're already tooled for and run over 270,000 tires per day just to barely keep up with new car production. To make radial tires requires new tooling and a different process. At the same time, quotas for the Big Three must be maintained with NO break in the steady flow of tire deliveries. This is nuts. The American tire producers didn't change over without a fight and car manufacturers had long-running contracts for bias-ply tires.

That's how Sears broke radial replacement tires into the American tire market. Car companies were slooooow to offer radials. Here's why CLICK HERE for the video.

I've never heard of 'driveshaft bushings'. Grand Marquis and Crown Victoria models have nearly identical steering and suspension as our Squarebirds. They also come with steel belted radial tires from Ford. - Dave

[dgs]

I've never heard of 'driveshaft bushings'. Grand Marquis and Crown Victoria models have nearly identical steering and suspension as our Squarebirds. They also come with steel belted radial tires from Ford. - Dave

Yeah, that doesn't make much sense does it. My 1996 BMW had a rubber isolator at the front of the driveshaft called a giubo and modern Mustangs do as well. I don't think any American cars of that era had anything like that. I was going from memory that there were changes in the drive shaft and bushings in the suspension to reduce the elevated road noise the radials transmitted. There was no real info on what those changes were, however.

I haven't read the article in probably 10 years, so it stands that those details might be a bit fuzzy.

I believe that the Thunderbirds from the late 60s & early 70s were some of the first to offer radials as an option, I've often wondered if there were radial vs. bias P/Ns for suspension bushings or the driveshaft for those cars. It's possible that those design changes had no adverse effect on bias tires' performance so they were simply adopted across the board. Or the article, or my memory, is wrong.

[simplyconnected]

My 1966 GTO's driveshaft had a rubber 'isolator' just behind the front U-joint but that was the only car I've ever had with that feature.
My 1990 Mustang's driveshaft was solid steel tube. - Dave

[pbf777]

With further research one will find many vehicles, particularly those equipt with automatics, of the 1960's and up, will have the two piece slip steel tube with an elastomer sleeve joining them together forming the driveshaft unit.

Scott.