Most of us have probably witnessed a tyre balancing machine proudly display “00” and “00,” only to find that the tyre and wheel combo still vibrates and shakes when on the vehicle. This not the fault of the balancer or the operator; the setup is indeed balanced out so that when spun on the balancer, there are no up-and down or side-to-side forces left. However, while everything is fine when the setup is spinning in the air, it’s a whole different story when it’s actually fitted to a vehicle.
To understand the concept of road force, we should think of the tyre as a number of springs poking out from the rim, because that’s what it really is. Think of it as a series of airbags instead of a continuous tyre (which also helps explain why tyres always go flat at the bottom). Unfortunately, tyres aren’t made of exactly equal springs all the way around, so there’s almost always a harder or softer spring in the pack somewhere around the circumference. As that “non conforming” spring hits the ground, it reacts differently from the rest, resulting in a tyre and wheel that doesn’t act balanced in real life, no matter what the regular dynamic spin balancer says.
Hunter’s new Road Fore Elite (RFE) is a machine that’s capable of measuring these forces in the tyre, and while it looks like one, it’s not even called a tire balancer – it’s a “Vibration Control System.”
A key feature of the Hunter RFE is a roller that’s pushed against the tyre with some 567kg of force as the tyre spins on the balancer. This serves the same purpose as a road test of the tyre and wheel, except instead of coming back with a vibration in the vehicle, and no real clue what to do next, the Hunter machine tells the operator exactly what’s wrong, where, and by how much.
Notice that we’ve written “tyre and wheel,” because to get it right, both have to be taken into consideration. An imperfection in the wheel can be made to offset one in the tyre, thereby getting the combo as true as possible before starting to throw weights at it. That’s how the manufacturers do it, using very costly machines called a Tyre Uniformity Grader (TUG) similar to the RFE in function, and it’s the main reason why OEM wheels generally have very little weight on them. Install a new set of tyres and /or wheels on your vehicle and we’ve lost the advantage of really balanced tyres and wheels. Sure, you’ve heard of rotating the tyre 180 degrees on the wheel and trying again. Well, the Hunter will tell exactly how many degrees to move the tyre, as well as check wheel and tyre runout with precision. By starting with the best possible positioning of the tyre relative to the wheel, the actual balancing becomes much easier and annoying vibrations can be eliminated. Not surprisingly, it was the luxury car market that prompted the Vibration Control System, but all vehicles can also reap the benefits of the new Hunter RFE.
To find out more about the RFE wheel balancer, or any other products in the Precision range, visit precisionautomotive.com.au or call 1300 366 252.
Written by Elton Lawes, Wheel Service Category Manager at Precision Automotive Equipment