Tires & Ride Quality
by Pat Goss
Tires - they do lot more than just get your car down the road; for better or worse, they can make or break your driving experience.
When you stop and think about it, tires are pretty amazing; they’re the only part of your car that actually touches the road. You know, back in the day, tires used to be built like this one on this old Chrysler; if you look at the wheel and then the tire itself, the tire is absolutely enormous. There is a tremendous amount of side wall there. Well, that meant that these old cars’ suspension didn’t have to do much because the tires themselves absorbed the bumps. All that side wall, it flexed and absorbed the energy. Well, that was good as far as ride was concerned, but it was horrible for handling because when you went around a corner, if you went too fast, the tire tended to roll under the wheel and you lost traction.
So tire engineers started decreasing the height of the side wall of tires. It’s called the aspect ratio, and here you can see one that is a little bit lower than the one on the Chrysler; this one is a little lower yet, and over here we have what is known as a 40-series tire. That series means that the distance from the wheel to the top of the tread is 40% of the width of the tread. So, the lower the profile, the shorter the side wall, the stiffer the side wall, the better the car goes around corners. Well, that has a lot of advantages, but, it also has some disadvantages.
You see, this tire is going to transmit a lot more road feel into the car, because there isn’t any side wall there to absorb anything. The other thing is, these tires are usually fitted on cars that have some form of sports suspension, so the suspension is tighter. Well, that means if there’s any kind of a problem with the balance of the tire or road force variation, it’s going to cause the tire to shake, you’re going to feel it in the car. Now, this particular tire – it has 24 pounds of road force, that’s a lot. But the tire manufacturer says it’s not a defect, because their criteria – 25 pounds of road force. So, on this particular car, anything above 50 miles per hour, the steering wheel shook like crazy; there was no way to fix it. The only fix was to buy another tire. So, if your car has low profile tires, before you buy replacements, you have to ask the question, what kind of a guarantee is the manufacturer going to give me against harshness in drive or vibration in ride. You want to make sure that the tires that you buy are guaranteed to ride smoothly. And if you have a question or comment, drop me a line, right here at MotorWeek.