Tire Balancing/Truing
Posted 11-02-2012 at 11:15 AM by mmartinkus
Have you ever had your tires balanced but were not totally satisfied with the outcome? It can become a frustrating experience at times if you have to return to the tire shop over and over trying to get a smooth ride especially if it is a new set of tires that seem out of balance.
Many times the cause is not that the tire(s) is out of balance but that it is out of round. When repeated attempts to balance fail, what the tire tech should be doing is checking run-out on the tire to see if it is oval shaped and if it is, can the lopsidedness can be corrected by rotating the tire 180 degrees on the wheel. Tires are seldom, if ever, perfectly round and the same is true for wheels. If the tire is mounted on the wheel in such a way that the "high" spots of both are aligned and the spots are high enough nothing will make the ride smooth. Rotating the two highs so that they are aligned 180 degrees from each other will many times minimize the problem.
There will always however be high spots and to get a really smooth ride what is needed is to "True" the tires. This involves either jacking the tire up while still mounted on the vehicle or placing the tire and wheel onto a machine that spins them while a "Shaving" device actually shaves off the high spots and making the tire round.
A note of caution here: Many RV's now days have 22.5" wheels and lots of those are cast aluminum. There are two different ways that these wheels are "piloted", either by the center hole or "Hub" or by the wheel studs. "Piloted" means the machining of the outside edge of the wheel where the tire mounts was machined true relative to either the hub or the studs. So if the tire shop that trues your tire is removing the tire and wheel assembly to mount into a machine for the shaving, they will need to know which way the wheel is piloted. They can usually do this with a visual inspection but it is critical in that if the hub piloted wheel is mounted and piloted by the studs in the truing machine, (or the other way around), the tire may not actually get trued and you will loose a little of your tire tread in the process.
I have actually had this happen in a shop near Atlanta. We had a vibration in a large motor home and after futile attempts to balance the tires we decided to send them out to a truck tire shop for truing. To save time we removed them and trucked them to the shop and retrieved them when finished. We remounted them on the coach and had the same vibration as before. We knew that they had trued the tires because you can see where the rubber had been shaved on each tire but just to be sure we called on a mobile balance/true tech to come check them out. He set up with the tires and wheels still mounted on the coach and started shaving rubber off the first tire. I asked how that could be if they had just been trued. He said that we had Hub piloted wheels on this coach and he knew for a fact that the outfit that we took the tires to originally had a machine for stud piloting because he had set the machine up for them when they bought it! When he finished the job for us that unit ran smooth as glass. We had encountered this balance problem with this brand of motor home many times before and when I quizzed our mobile guy he said that he knew for a fact that the factory that was building this particular brand had a true machine that was wrong for the wheels.
On a different topic...ever notice how some polished wheels are lots shinier than others? Its because the owner shines them more often. Every time you shine those wheels they get just a little shinier than they were. Acid washing the wheels prior to polishing will ensure that the grit on the wheels will not get ground into the surface of the aluminum. The new wheels when finished have tiny scratches in them that can't be seen by the naked eye. When they get polished each time the ridges of those scratches are knocked down just a little bit and over many polishing s they start to disappear leaving a progressively shinier surface each time. A good looking set of shiny wheels can overcome many appearance ills. Shine em up! It's a good job for a high school-er!
Many times the cause is not that the tire(s) is out of balance but that it is out of round. When repeated attempts to balance fail, what the tire tech should be doing is checking run-out on the tire to see if it is oval shaped and if it is, can the lopsidedness can be corrected by rotating the tire 180 degrees on the wheel. Tires are seldom, if ever, perfectly round and the same is true for wheels. If the tire is mounted on the wheel in such a way that the "high" spots of both are aligned and the spots are high enough nothing will make the ride smooth. Rotating the two highs so that they are aligned 180 degrees from each other will many times minimize the problem.
There will always however be high spots and to get a really smooth ride what is needed is to "True" the tires. This involves either jacking the tire up while still mounted on the vehicle or placing the tire and wheel onto a machine that spins them while a "Shaving" device actually shaves off the high spots and making the tire round.
A note of caution here: Many RV's now days have 22.5" wheels and lots of those are cast aluminum. There are two different ways that these wheels are "piloted", either by the center hole or "Hub" or by the wheel studs. "Piloted" means the machining of the outside edge of the wheel where the tire mounts was machined true relative to either the hub or the studs. So if the tire shop that trues your tire is removing the tire and wheel assembly to mount into a machine for the shaving, they will need to know which way the wheel is piloted. They can usually do this with a visual inspection but it is critical in that if the hub piloted wheel is mounted and piloted by the studs in the truing machine, (or the other way around), the tire may not actually get trued and you will loose a little of your tire tread in the process.
I have actually had this happen in a shop near Atlanta. We had a vibration in a large motor home and after futile attempts to balance the tires we decided to send them out to a truck tire shop for truing. To save time we removed them and trucked them to the shop and retrieved them when finished. We remounted them on the coach and had the same vibration as before. We knew that they had trued the tires because you can see where the rubber had been shaved on each tire but just to be sure we called on a mobile balance/true tech to come check them out. He set up with the tires and wheels still mounted on the coach and started shaving rubber off the first tire. I asked how that could be if they had just been trued. He said that we had Hub piloted wheels on this coach and he knew for a fact that the outfit that we took the tires to originally had a machine for stud piloting because he had set the machine up for them when they bought it! When he finished the job for us that unit ran smooth as glass. We had encountered this balance problem with this brand of motor home many times before and when I quizzed our mobile guy he said that he knew for a fact that the factory that was building this particular brand had a true machine that was wrong for the wheels.
On a different topic...ever notice how some polished wheels are lots shinier than others? Its because the owner shines them more often. Every time you shine those wheels they get just a little shinier than they were. Acid washing the wheels prior to polishing will ensure that the grit on the wheels will not get ground into the surface of the aluminum. The new wheels when finished have tiny scratches in them that can't be seen by the naked eye. When they get polished each time the ridges of those scratches are knocked down just a little bit and over many polishing s they start to disappear leaving a progressively shinier surface each time. A good looking set of shiny wheels can overcome many appearance ills. Shine em up! It's a good job for a high school-er!
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Comments
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I am looking for a shop that does this in the Portland, Or area and have not been successful. All of the articles and comments that I see are older. Is this an older process that has gone away?Posted 02-12-2015 at 09:47 AM by Peterd503 
