Run Flat Tires
I have run flat tires on my car. Sure, it came with them, but I’ve grown to love them. Yes, they are a little more expensive, especially when filled with nitrogen, and most of them cannot be repaired, only replaced, which hikes the cost of ownership substantially. Despite these obvious drawbacks, they give me a level of peace of mind. I will never be stuck on the side of the highway or on a country road with a flat. I don’t even have to try to remember how to change a tire, and yes, I do know how. In fact, my car doesn’t even have a spare, since my run flats will get me to safety.
Run flat tires are designed to keep performing while they are deflating, or even when deflated. Drivers can continue to drive their vehicle for up to 80 km at speeds of up to 80 km/h, and get to a safe place or service centre.
You don’t want to put run flat tires on a vehicle that wasn’t built with them in mind. First of all, they need to work in conjunction with a tire pressure monitoring system. Most cars built after 2007 have one, it’s required by law. Without the pressure monitor, one of the tires could be running at zero air pressure, overheat, and cause the driver to lose control of the car. In the late 1990s, Firestone tires were found to be responsible for more than 100 fatalities, because they ran under inflated, blew out or delaminated and caused vehicles to rollover.
Tires and suspension work hand in hand. Suspension is engineered to take into account how tires react under load, cornering or braking, and sidewall flex is taken into consideration. The sidewalls on run flat tires do not compress much at all, and so react differently on hard corners. BMWs for example, have suspensions that were designed for run flat tires. Most BMWs and MINIs come with run flats as standard equipment, and count on them to support their Efficient Dynamics Strategy, which allows the car to have a 50-50 weight ratio by eliminating the extra weight of a spare, jack and tools, to give the car better balance, lighter weight and greater fuel economy.
When asked about swapping out expensive run flat tires for conventional ones, Monty Roberts from BMW’s Product and Technology department was clear. “We do not recommend replacing run flat tires with conventional tires,” he said, “that deviates away from the original design, safety and suspension calibration technology that the run flats were originally designed for.”
Whether you opt for run flat tires or conventional, an investment in quality tires is never a waste of money.
By Linda Aylesworth – car-news.ca