Are My Tires Causing the Car to Vibrate?
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Own a car long enough, and one day it may begin vibrating while you're driving. This usually signals a tire problem. Here's what you need to know.
The Most Common Causes of Tire Vibration
Modern vehicles are designed to drive smoothly, even on not-so-perfect road surfaces. Although some mild vibrations when driving can be normal, significant vibrations indicate something is wrong.
Vehicles have so many spinning and moving parts that all kinds of things can cause vibrations. Those vibrations resonate through the car, causing it to shake. Fortunately, tires or wheels are the most likely cause of vibrations, and those are easily repaired or replaced by your repair shop.
Over- or Under-Inflated Tires
Over-inflated tires act like a bouncing ball. Sidewall stiffness and tread rigidity may trigger vibrations, providing less tire-to-road contact area and causing the tread to quickly wear in the center. Tires affected this way are prone to damage and blowouts.
Under-inflated tires quickly overheat and wear abnormally at the outer edges, leading to low and high-speed vibrations. In addition, rolling resistance greatly increases (think about pedaling a bicycle with a flat tire). That causes tire temperatures to rise significantly, to the point the tire tread separates from the tire body. A blowout often follows.
Note: Temperature has a dramatic effect on tire pressure. Tires heat up and expand under normal driving conditions. Extended, excessive or aggressive stop-and-go driving, especially on ridiculously hot days, greatly increases air pressure in an already over-inflated tire, while greatly increasing the temperature of an already under-inflated tire — the perfect conditions for a blowout.
Proper tire inflation is critical not only for driving safety, but also to increase the life of your tires and improve fuel economy. Checking tire pressure needs to be part of your monthly DIY car maintenance routine.
Worn Down Tires
Examine your tires for abnormal wear and check that they are properly inflated. Tires that are bald, badly worn or worn unevenly are a likely source of low and/or high-speed vibrations. They also negatively impact braking, steering responsiveness and control.
Inspect the sidewalls for dry-rot cracking, bubbles or bulges (usually caused by a broken tire belt), and the tread area for flat spots or tread separation. A tire with a broken belt will produce a rhythmic thumping sound and a low speed vibration and/or wobble. Never drive on a tire that has a bulge, tread separating from the tire body, exposed metal or fiber cords, or has separated from the wheel. Water can enter the gap between the tire and wheel, causing all kinds of vibrations after being filled with air and driven.
Flat spots are caused by extreme braking or the vehicle being parked for days, especially if the tires are under-inflated. Tires with flat spots make a thumping sound and vibrate when the flat spot meets the road. Flat-spotting is usually temporary, rounding out while driving as the tire warms up. However, in the worse cases the flat spot is permanent and it’s time for new tires.
A bent, cracked or damaged wheel can cause your vehicle to vibrate. This is more common than you might think. Hitting a pothole, bouncing into a curb or getting walloped in an accident can damage a wheel.
Customarily, wheel balancing will negate minor wheel issues. However, if a wheel is the suspected cause of a vibration, your mechanic will need to measure wheel run-out (roundness) and check for other deformities. Severely bent or out-of-round wheels will need to be repaired (if possible, by a highly specialized wheel repair service) or replaced. Wheel diagnostics and repairs are something definitely left to the pros.
Out-of-balance tires and wheels vibrate up and down or side to side at specific speeds. Having your tires and wheels professionally balanced (approximately $50 to $100) almost always fixes this problem.
As a tire’s tread wears down, the tire become lighter and needs to be rebalanced. Balancing involves adding weights to the edges of the wheel to eliminate tire vibrations. Although rare, if you detect a slight vibration and notice a one- to three-inch rectangular discoloration or stain on the wheel, a wheel weight may have fallen off and the tire will need to be rebalanced.
Wheel Alignment / Abnormal Tire Wear
Abnormal tire wear (cupping, scalloping, feathering) from an out-of-alignment or damaged suspension system will cause tires to be noisy and vibrate. Your repair shop should check for worn or bent suspension parts as part of a wheel alignment or when diagnosing abnormal tire wear.
Your driving safety depends on performing basic tire maintenance. Pick up a tread depth gauge and air pressure gauge online or at your local auto parts store and use them regularly. Replace any tire that has tread measuring 4/32-in. or less. Tires inflated to the manufacturer’s recommended pressure, visual inspections, tire rotations and wheel balancing can extend the life of your tires while also preventing annoying vibrations.