Q Recently when buying two new tires for my front-wheel-drive car, I was told the company policy is to put the two new tires on the rear. Their rationale: In a skid they would have more traction and tend to straighten the car out. In theory, this is correct if no other control action is taken.
I watched a video showing a car with the newer tires on the front going into a skid and spinning out. Watching the front wheels, I could see no action to steer out of the skid. Conclusion: The recommendation is valid for dead people driving cars.
In a front-wheel-drive car, the front tires steer, drive and provide most of the braking, thus it makes sense to me to put the best tires on the front. I suspect that the tire companies expect to sell more tires by having the worn tires on the front that will need replacement sooner. What's your opinion?
A You are correct, and you've already answered the question: Brain-dead people drive cars. The mandate from tire companies require tire dealers, when a customer purchases just two new tires, to install the new tires on the rear axle, regardless of which end drives the vehicle. The reason, I strongly suspect, is motivated by liability concerns rather than available traction. I also suspect that this policy is the result of lawsuits rather than real-world tire testing.
You've identified the pertinent facts. The front tires on any vehicle do all the steering and most of the braking. On a front-wheel-drive vehicle, the percentage of braking is even higher, and these same tires also provide all of the acceleration. Logically, the best tires should be on the front.
Tires with significantly less tread are far more prone to losing traction in slippery conditions. When traction is lost, the tires with the least grip will try to "lead" the car. In other words, if the front tires lose traction first, the vehicle would "understeer" -- it would tend to continue straight ahead in the direction of travel. At least you see what you are about to hit! What's the fix for this? Ease back the power or modulate braking to allow the front tires to regain traction and begin to steer the vehicle again.
If the rear tires lose traction first, the back end of the vehicle will try to pass the front -- the vehicle will rotate around the front tires. What's the fix for oversteer? Look where you need the vehicle to go, ease back the throttle or brake to help the rear tires regain traction -- hopefully -- turn the steering wheel in the direction the rear end is trying to go -- instantly and exactly the right amount -- then anticipate the rear end hooking back in the opposite direction like a pendulum if and when the rear tires regain traction, requiring you to steer back in that direction -- instantly and exactly the right amount.
Obviously, loss of traction in the rear is far more difficult to correct than loss of front tire traction. That's why modern antilock brake, traction and stability control systems are effective in reducing loss of control. These systems react more quickly, correctly and far more precisely than drivers.
