In a perfect world, if wheels were perfectly machined, tyres perfectly round, and their casings and compounds were entirely uniform in properties, there would be no need for tyre balancing. But there are always going to be margins of error and variances in the above.
An average tyre can weigh 20 pounds or so and generate a massive amount of centrifugal force at high speeds. Any variation in roundness or weight distribution leads to vibration issues.
Costs of Tyre Balancing
The cost of balancing tyres is usually a package price for all four and varies from about £35 to £70. There are two basic types of balancing: dual plane and static.
Dual plane (or “dynamic”) balancing splits the wheel into two planes: the inner and the outer, and balances them both down to zero separately. This is generally the most common and recommended.
Not all rims are designed for that, and often a static or single plane balance is done. That looks at the wheel as a single plane and applies balancing weights only at the center-line of the wheel.
The procedure is about the same either way, and the cost of getting your tyres balanced is most often the same. Usually, the decision about what balance method will work best is left up to the mechanic doing the work.
What Exactly is Tyre Balancing
Think of it like swinging a small weight on a string in a circle over your head. Whenever the weight is at the point of rotation, it pulls your hand toward that point.
A tyre balancer spins the wheel and looks for that pull. It then calculates an exactly equal weight to be placed exactly opposite to the pull, effectively cancelling out the imbalance and, ideally, leaving exactly zero side-forces at the centre point.
When road-speed-dependent vibrations are felt in an automobile, the general rule is that it will be a rotating part that is out of round or out of balance. By far, the most common cause is a wheel out of balance.
If you feel it in the steering wheel, it’s probably the front tyre. On the other hand, when you feel it in the rear chassis, it’s usually a rear tyre. It’s most common and recommended that, when it’s necessary to check a tyre for balance, you just go ahead and check them all and rebalance as necessary.
Road Force Balancing
The above balancing description refers to the old and common method of zeroing out the weight-related side forces at the centre of a wheel’s rotation. Another less common problem is from road force vibrations, where there is a variance in either the roundness of the tyre or wheel or the stiffness of the tyre sidewall.
Either one of these can also cause road-speed-dependent vibrations. A road force balancer is a machine designed to correct that.
It spins the wheel while using a roller to bear against the tyre surface just as the road would. Then, it calculates the lowest point of the rim and the stiffest point of the tyre sidewall and indicates those two points.
Rather than simply applying weights, this requires the tyre beads to be dismounted, and then the tyre is shifted on the wheel to the ideal position indicated by the machine. After this, conventional balancing still needs to be done.
The price of road force wheel balancing varies from about £40 to £100. It’s worth noting that road force-induced vibration problems are rarely noticeable, and road force balancing is often only done when conventional balancing has failed to resolve vibration issues.
The machines are also more expensive and less common. Shops in many areas, if they don’t have a road force balancer, will often sublet vehicles needing that service to a shop that does if necessary.
If conventional balancing doesn’t resolve an issue, road force balancing is also a good way to check the tyre for out-of-roundness, to check for flat spots on the tyre, and to rule out a bent rim. In both cases, the tyre/rim assembly can be perfectly balanced but still cause noticeable problems on the road.
A road force balance should catch any of those problems if they are not otherwise obvious.
Tips for Getting the Best Service
- If possible, go back to the shop where the tyres were purchased. Many shops will rebalance the tyres they installed for free and will have some incentive to do the work quickly and well to keep you as a customer.
- Pay attention to exactly when the problem occurs. A wheel balance issue will usually be most noticeable at certain speeds – 50 to 75 mph, typically. A tyre roundness or road force issue is usually more noticeable at lower speeds. Letting the shop know when the problem occurs helps greatly in diagnosing the problem and verifying that it has been solved.
- Allow time for the work to be done. If it’s a simple rebalance, it’s common enough to have the service done while waiting, as it takes only about half an hour. But if the problem isn’t easily resolved, then, more than one attempt might be necessary and the vehicle might need to be test driven more than once.
- Rule out other problems. One of the most common non-mechanical things that can cause an imbalance, especially in winter, is mud, ice, or debris in the wheels. Cleaning or hosing out the wheels is one thing that tyre shops have to do regularly before balancing tyres.
What Can Go Wrong
The most common problem is that wheel weights can fall off. Weights are of two types: either clip-on or adhesive mount.
Adhesives don’t always stick perfectly, and it’s often a challenge to prepare a dirty, rusted, or even corroded rim surface adequately for good adhesion. Clip-on weights have a few varieties to fit different rim profiles, but there are far more different rim profiles than there are wheel weight varieties.
In most cases, the shop will use what fits best, but sometimes a weight will work loose. If the weight comes off, the wheel is no longer in balance and vibration might be felt.
The simple solution is to take the vehicle back to the shop and let them know. It is quite common to have to re-check tyre balances.