Bad vibrations?

The end of summer is when many people take their vacations and for some, it is time for their annual road trip with their families. You are cruising down the freeway in your car or SUV when you start to notice some vibration but only at high speeds.

Why do these vibrations happen? Obviously, there are many things that can cause it but in this article, we will address the topic of wheel and tyre balancing, which tend to be the most common cause for the vibrations. Fortunately, it is not something that is hard to rectify. These days, you can pull into a tyre shop that can balance your tyres and wheels in a matter of minutes for a minimal amount of money.

Why it happens

Generally, you will get the vibration if your wheels and/or tyres are "not round enough". Is that possible? Aren't wheels and tyres supposed to be round? Yes, but many times, they are not PERFECTLY round which is the cause of the problem.

Wheels are measured in two directions: radially and laterally. Radial run-out is measured by using the center of the wheel and going outwards. If you look at a wheel from its side and spin it from its hub, any variance in the spin will be the radial run-out. Now, look at a wheel from the edge. If there is any side-to-side movement when you spin it, you will be observing lateral run-out. There are specifications on how much radial or lateral run-out is acceptable in the auto industry but obviously, the less the better. At some point, the excessive run-out will translate into wheel/ tyre vibration.

As with wheels, tyres can have excessive radial and lateral run-out as well, which will present a similar problem. ) Tyres that have excessive radial run-out can sometimes be trued (also referred to as "shaved") where the tyres are mounted on a machine that shaves off rubber on the high spots.

 

Loaded force variance is another defect found in tyres that can cause vibration. Put a wheel and tyre combo on a balancer and while it shows that it is perfectly balanced, a vibration might be felt because of this force. This refers to the internal defects within the tyre. All tyres have variances in sidewall stiffness. As the tyres roll with a load on them and they roll onto a softer section of the sidewall, the vehicle will settle slightly. As it rolls to a stiffer part of the sidewall, the vehicle will rise slightly. If the variance in sidewall stiffness is too much, you will feel it as a vibration.

Balancing act

Wheel/tyre combos can be balanced in many different ways. The most common method is dynamic balancing, but there are also a number of permanent balancing systems.

 

Tyres and wheels can be balanced using a technique called position balancing. This procedure can reduce the overall amount of radial run-out from the tyre/wheel combo. Typically, this is done by doing a radial run-out test on the wheels and then again with the wheel/tyre combo. The idea behind this technique is to find the high spot on the wheel and try to match it up to the low spot on the tyre. In essence, we are trying to reduce the total radial run-out of the wheel/tyre combo. This technique is not normally done as it can be very time-consuming.

 

Dynamic balancing is also commonly known as spin balancing. It is normally performed using computerized spin balancers. The technician clamps the wheel/tyre onto the machine, sets the wheel dimensions, spins it up and then the machine calculates the locations and amount of weights to apply to the rim.

 

Another method that is not very commonly used but has come to my attention is the patented Centramatic Balancers. 

Centramatic Wheel Balancers

With these "on board" balancing systems, you may never have to have your wheel/tyre combo balanced by another shop again. The Centramatic Balancers claim to maximize tyre life as well as offer a smooth ride. The disc shaped balancers are mounted permanently behind the wheels and use centrifugal forces and deflection from rotation to automatically distribute free moving weights that are sealed within the balancer. By distributing the weight where needed, the balancer will minimize radial run-out and provide a vibration-free ride. Why more people don't use these Balancers is beyond me. It would seem that this would ensure perfect balancing throughout the life of the tyres and even when you replace the tyres with new ones, you will save money in the long run by not having to have the shop balance them for you. (Editor's note: Please click here to read our review of the Centramatic Wheel Balancers)

 

Smooth sailing

 

There is absolutely no reason why your freeway drives have to be bone-jarring back-breakers these days with the many methods and techniques available to balance out your wheels and tyres. Getting a smooth enjoyable ride out of your vehicle may not be as complicated as you think. Maybe with a smoother ride on long trips, your children will be less likely to repeatedly ask, "Mom, Dad...are we there yet???"

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