Rolling Down The Highway: How To Mount & Balance Wheels & Tires Part II
Wayne Scraba
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In our last issue, we began our look at mounting tires and balancing the wheel and tire combination. The first segment took a close look at physically mounting the tire. As we pointed out then, more wheels and tires are damaged by improper mounting than you might imagine. That’s why following proper mounting procedures proves critical. Balancing can’t really damage the wheel and tire combination, but it can lead to plenty of bad vibes down the road. Given that, we’ll dig deeper into the balancing part of the equation with this segment. Check it out:
When it comes to balancing you have a couple of options: Use a good old-fashioned bubble balancer or, as shown here, by way of a modern spin balancer. When balancing a tire, keep in mind there are two types of imbalance you’ll most likely encounter: “Static” imbalance or “dynamic” imbalance. Static imbalance is vertical movement resulting from heavy or light spots in a tire. This imbalance can be corrected using either a static bubble balancer or a dynamic spin balancer. On the other hand, dynamic imbalance is caused by lateral movement (wobble or shimmy) that comes from unequal weight on both sides of the tire and wheel/wheel assembly centerline. This imbalance can only be corrected with a dynamic spin balancer.
In case you’re wondering, dynamic balancing doesn’t mean the ugly weights have to be placed on the outside. A proficient tire technician can manipulate the setup so that the weights all tuck on the backside of the wheel. Another issue is tires “out of round.” It’s not that common on modern tires, but with vintage bias ply rubber, there’s always a possibility the tire has high spots. In fact, just before the radial became uber-popular (early seventies), plenty of tire shops “trued” out of round tires. Essentially, this process literally shaves the mounted tire with sharp blades as it’s spun by a machine. The reason for truing the tires was (and still is, if you have vintage rubber on your car) because you’d often find a bias ply tire or even a complete set could not be balanced. You’d end up with a vibration at one speed or another. Greybeards will remember how this vibration grief drove you nuts. Truing was the only answer. After the tires were trued, they could be balanced. And yes, there are select shops out there today who still do the work (think places that mount and balance big truck tires).
A modern tire balancer, such as this Hofman Geodyna Optima, is pretty much hands-free once the wheel and tire are mounted. A laser system determines where the weights go and how much weight is required.
By manipulating the weight location, the technician can hide the tape weight on the backside of the wheel. In fact, this setup allows the technician to hide the weights behind wheel spokes. While more common on wheels and tires destined for racing, some shops add a strip of Duck tape over the tape weight when complete.
Nitrogen for tires is nothing new, but here’s a short refresher: One of the big benefits of filling your tires with nitrogen is the fact that air pressure is more easily retained. According to Ingersoll Rand, “diffusion out of the tire sidewall is 30 to 40 percent slower than oxygen. That’s why a nitrogen filled tire maintains pressure longer.”
For street driven cars, an even bigger benefit could be the fact that nitrogen prevents oxidation. Oxidation leads to tread separation, but it also leads to corrosion of the rim. Don’t believe it? Forget to drain an air compressor after a few days of use and you’ll see just how much water is found in good fashioned compressed air. So what’s the downside? That’s simple. Most of us don’t have nitrogen refill stations in our own shops. You have to take the car to a shop and have the tires filled when required. And the key for refills is usually the green filler hose (shown in the second photo). Nitrogen refill stations are often green in color too.
At this point, the tires pressure is checked, tires are marked for their respective sides (important if they’re directional) and they’re rolled out for mounting (or tossed into the back of the pickup truck). It’s a done deal.
