Monday, February 20, 2006

Tire positioning - A change in philosophy

For as long as I can remember, conventional wisdom has had the car industry making sure the best 2 tires are on the front of any vehicle that is in for service. This weekend, I had to think twice about my beliefs after reading a column by John Mahler in The Star's Wheels section.

The belief has always been that most driver's are safer with the best tires on the front, as that ensures that they will have the most control of their steering. Mahler however points out that there is more to the equation than front end grip. He reminds us that todays vehicles are designed to keep their occupants safe in a straight, frontal collision. Also, when a vehicle is braking hard, weight is transferred away from the rear tires, which lessens grip. This combination creates a vehicle which is more likely to spin in an emergency situation. Given that most vehicles are designed to hit things straight on, not sideways or backwards, it makes sense that you don't want a vehicle that spins too easily. Having more traction in the rear will create an understeer (pushing) condition, which in effect ensures that an out of control vehicle is more likely to hit it's target straight on.

Years of advice thrown right out the window! It just shows that no matter how long you work in your chosen industry, you can still learn something. Thanks John.


Blogger Harvey said...

Dear Sir, Please be informed that front wheel drive vehicles have a front to rear weight ratio ranging from 58% on the front ,42% on the rear to 66% on the front,34% on the rear.
Using figures from Fatality Analysis Reporting System and comparing them to
the front/ rear weight ratios of front wheel drive vehicles, I have found there is a direct correlation between fatalities and weight ratio. For example a 62/38 ratio vehicle will always have more fatalities than a 60/40 ratio vehicle. With an average of the increase in fatalities due to the decrease in rear traction it proves an increase of 2 fatalities for every point one percent increase of front traction over rear. I have written a report showing this relationship and made a demonstration DVD.

6:24 PM  

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