The main signs of an imbalanced tire or tires are:
• Uneven wear
• Increased fuel usage
• Suspension issues
• Tire/wheel runout
• Vehicle sensors (ABS, brake control module).
If you notice any of these irregularities, make sure to check tire balance, even if the tires are relatively new.
When your tires are out of balance, you may feel irregular vibration at 40-45 mph. It usually worsens as you increase the speed, and can cause vehicle occupant drowsiness. The tremor may be too insignificant for you to notice if you only drive along quiet streets. This is because some vibrations don’t occur until the car reaches 50-70 mph.
The type and intensity of vibration may depend on the weight and size of the wheels and the vehicle. The vibration also differs by the level of steering/suspension sensitivity towards vibration. Also, keep in mind that out-of-balance tires are not the only possible cause of vehicle vibration.
If your tires are out of balance, they may eventually patch-wear. This is one type of tire wear pattern that is mostly random, meaning that it wears in different spots around the circumference. This happens because of the vibration and shaking that imbalanced tires causes.
You can check treadwear if you have any suspicions, using the penny test, tread depth gauge, etc. Make sure you don’t check just one spot, go around the tire, and in and out. If you see a difference in 1/16” or more, your tires are wearing unevenly. And if the wear is in random flat spots, it’s most likely because of imbalance.
Bearings, shocks, and other elements of a car’s suspension may suffer, due to frequent vibration. This happens because of the partial loss of traction and vibration, since the tires are out of balance. Moreover, problems with suspension usually cause cupping – a type of treadwear that appears in regular spots across the tire. It may also contribute to the vibration of the vehicle and partial traction loss, which will cause more damage.
Increased Fuel Usage
When tires are out of balance, they often partially lose traction with the road, increasing fuel consumption. 1 oz of imbalance at 60 mph usually causes 7.73 pounds of excess force per revolution. And for every extra 7.73 pounds, a vehicle will use an equal amount of excess fuel.
Fuel economy also depends on the severity of the imbalance, the type of tires, and the speed. The greater the imbalance and the higher the speed, the more fuel waste there is. The heavier the tires with the imbalance, the less fuel efficient the car becomes.
Furthermore, tires provide greater fuel efficiency when they are 50-80% worn. However, if the tires are out of balance they wear unevenly, which makes them inoperable sooner. These facts relate to all kinds of driving tires.
According to the American Trucking Association’s Technology & Maintenance Council (TMP), tire balancing is a highly recommended practice. Even trailer tires, which usually lack attention, should be in balance, to maintain and even improve fuel economy.
Tire/wheel runout is when the tire isn’t perfectly round, which is both a sign and cause of imbalance. If the high spot of the wheel aligns with the high spot of the tire, the imbalance is greater. The runout can be radial or lateral, meaning that the tire may be deformed vertically or on the sides.
Tire technicians usually manage to balance runouts by match-mounting the tire on the wheel. Eventually, the high spots balance each other, and if there are no other issues, the vibration disappears. For the tires to operate regularly, the runout should be no more than .030” to .050”.
Vehicle Sensors (ABS, brake control module)
A team of researchers from SAE International (initially the Society of Automotive Engineers) used anti-lock braking system (ABS) wheel speed sensors and brake control module data, in order to recognize tire imbalance. They managed to detect whether tires are out of balance while on the go, and developed a two-stage system based on the results. In 2011, the researchers introduced a paper proving this.
The Difference Between Tire Balancing and Wheel Alignment
Many drivers confuse these two terms. Tire balancing is achieving equal distribution of weight around the circumference of the tire. Wheel alignment is adjusting the wheel’s position so it’s perfectly perpendicular to the ground and parallel to other wheels.
You should balance your tires every 3,000-6,000 miles (5,000-10,000km), or 1-2 years if you use your vehicle regularly. You should also consider balancing your tires and wheels if/when you:
• Buy new tires, rims, or wheels
• Rotate the tires
• Repair the tires
• Notice vibration at higher speeds
• Notice uneven treadwear
• Hit a big pothole.
Remember that the balance of your tires may disappear as the tire wears, and the weight distribution alters. Also, everyday stress, bad roads, hard braking and cornering, etc., may disrupt the balance over time. So, balancing new tires once you mount them may not be enough.