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Automatic Tire Balancing Using Airsoft Pellets |
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| Category: | Tires | |
| Author: | Eric | |
| Date: | April 22nd, 2005 | |
Why Reinvent the Wheel Weight?
So traditional wheel balancing sounds okay, but here is the problem. The larger the tire, the further away from the wheel the tire gets. That means the balancing weights are further from the tread and it requires more weight to balance the tire. Also, a larger tire weighs more overall and potentially could require more counter weights to balance the tire’s greater mass. Add these two things together and there could me a lot of weight on the side of your wheel.
First of all, having 6†of wheel covered with weights is ugly and they can damage the finish on the wheel. Second of all, it’s bound to get knocked off when you come in contact with a rock. It will happen eventually if you drive on rocks. You probably won’t notice until you stop to air your tires up and that weight will be long gone and your tire is now out of balance.
The other problem is tire wear and how it affects tire balance. Tires don’t always wear evenly. Even when they do, the weight distribution can change putting your tire out of balance. The only solution to this is to get your tires re-balanced every 10k miles or do one of the following.
This idea isn’t really new, but the way you apply it has matured quite a bit. The idea is to move the weight as far to the outside of the tire as possible and to make it so the tire is always in perfect balance. The way to do that is to put weight inside the tire which is as far away from the center of the wheel you can get and use some sort of material that can freely move around to naturally balance the tire when it spins.
How it Works
The physics of how/why the free mass inside the tire automatically knows where to go is hard to conceptualize. The best way to understand why this works is to exaggerate the problem. Imagine there is a 5 lb weight fixed to one place on the tire. When you spin that tire to normal high way speeds, it will be so terribly out of balance that the tire would probably hope off the ground with every rotation. The axis of rotation is actually moved away from the center of the wheel toward this extra mass because it’s pulling the whole tire with it as it spins. The free moving balancing weights inside the tire are not affected the same way by these forces. First as you get up to speed, centripetal force will make the balancing weight stick to the inside of the tire. Then the force of the imbalanced weight on the tire will move this balancing weight away from the imbalance. When enough of the mass is opposite of the imbalance, the vibration disappears and the axis that the tire is rotating on returns back to the center.
To give you another example to explain why the balancing weight moves away from the imbalance and balances the system, think about what happens when you accelerate fast in a car. Anything that’s loose moves to the back of the vehicle. This same force is created on an imbalanced spinning tire. The imbalance is jerking the tire sending the free mass inside away from it and the centripital force holds it here.
What to Use
Okay, so we know the theory about why it works, but what do you use for the weight inside your tire? Over the years people have used some pretty strange things from golf balls, steel BBs to water. None of these are very good at balancing your tires. Golf balls have too much mass for each unit so they can’t balance a tire as evenly as using many more less massive weights. BBs work well to evenly balance the tire because they’re small and heavy, but their material is their downfall. Moisture does exist in your tire unless you always fill them with Nitrogen. The BBs will eventually rust and completely disintegrate over time.
1 KG of common Airsoft pellets
Water can work, but it is slower to align itself because of its high surface tension. Also, since you wouldn’t use much, as far as volume, the water would have to spread thin and would likely evaporate after a season’s worth of airing down your tires. Other substances like Nu-Mag, Equal, Magnum and other balancing powders are susceptible to clumping as they absorb this same moisture and they're not round, so they don't roll into position quickly.
There are a couple of commercially available products designed just for balancing tires. One company in particular, Innovative Balancing, has developed a product that works very well. They call them Dyna Beads. They are small ceramic balls that can be inserted through the valve stem. Since they are perfectly round, they quickly roll into position and adapt to balancing changes. They will not clump from moisture inside the tire. Since the media is small, they recommend a filtered valve stem so you don’t loose any of the media when air is released.
Compared to other media and bolt on balancers, the Dyna Beads are a bargain. On average, to buy the media, filtered valve cores and the removal tool for four tires, you’re looking at about $60. They claim their beads reduce the operating temperature of the tire and can extend tread life 35%. They have also developed a great chart which you can use to determine how much balancing media you need. Use it here, http://www.innovativebalancing.com/BigTirechart.htm.
Always one to save a buck or two at the expense of some effort, I found Airsoft pellets to be an excellent alternative that has most of the benefits of Dyna Beads and none of the drawbacks of the alternatives. Airsoft pellets are too large to fill through the valve stem and they are less massive per unit, so they’re not as efficient as Dyna Beads, but still very good. They are perfectly round balls of high density plastic which will not clump from moisture or breakdown over time. I ordered 2 KG of pellets online for $26 shipped to my door.
Steel BBs that rusted. Pic courtesy of InnovativeBalancing.com
Installation (1 hr)
I got creative, but you can use a Hi-Lift jack to unseat the bead of your tires. Simply remove all of the air from the tire by removing the valve stem and place the base of the Hi-Lift right where the bead seats on the tire. Then position the jack underneight something heavy like a sturdy work bench or your rig and begin jacking. Once you get the hange of it, you can do all four in less than an hour. Please be careful, Hi-Lifts are dangerous and mix this with putting a lot of force on an unstable tire, you could get hurt. There are other products like Tyreplyers which are supposed to work well. Using Innovative Balancing’s chart above to determine how much media to use, I dumped the pellets in and reseated the tire. One of the beauties of this system is its okay if you put more than the recommended amounts. In fact, it’s better to go over than under because the extra material will just find a neutral place inside the tire and will not affect the balance.
Results
Now take it out and enjoy tires that are rebalanced every time you drive. I have to get up to about 20 mph for the pellets to stick to the inside of the tire and begin working. It’s at speeds greater than 20 when tires need to be balanced. They will not fall off the tire until a you’re below 5 mph. I can hear the pellets fall off when the window is down, but otherwise, I never notice they are there. My tires have never been balanced and they are worn very unevenly and ride terribly on the road. After using the pellets, the operation was noticeably smoother and quieter. All of the uneven wear has evened out. I’m sure using them from the beginning when the tires are new will yield greater gains than I have. I have yet to confirm the extended tread life claims because that’s impossible to measure. Your driving habbits will influence this a lot.