Rear engine vehicles usually have a larger portion of their weight over the rear wheels. That provides an exciting driving experience if handled correctly. But it also gives the engineers something to be concerned about. How do you design the car to handle well despite the difference between front and rear?
With the Corvair, Chevy’s engineers used differing tire pressures to handle the “problem.” While we’re used to 32 lbs front and rear, the manual calls for 18 lbs front and 30 lbs rear. That just doesn’t seem right to me. When I checked the air in my tires a few weeks ago, I just couldn’t do it. I put 22 in the front and 30 in the back. But after reading an explanation by Brent Covey, I’m beginning to think I should let some air out of the front tires.
In a car with a lot of weight at one end you have some options for reducing the slip angle of the tires on the ‘heavy’ end: larger tires and/or higher tire pressure and/or reducing roll stiffness. … The early Corvair has tremendous rear roll stiffness and swing axles don’t let you reduce it much, even with softer springs and considerably increased front roll stiffness, so tire pressures were pretty nearly the only tool that would really make a difference on earlies – the lates have very weak rear roll stiffness and this is mostly why they are inherently better handling cars. Most efforts to tame the Corvair are focused on increasing front roll stiffness to transfer cornering loads onto the front wheels to minimize the possibility the rear will generate larger slip angles than the front.
The rest of the article gives technical explanations for things like tire slip and how GM handled the problem with the Pontiac Fiero, wagons, and most trucks. If you would like to get a better understanding of how suspensions, steering, and tire pressure go together, this is a good article to read.