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RADIAL RUNOUT
We all want a smooth ride and we have had many posts relating to things like centramatics and ballancing media (Equal).
So let’s start this discussion about tire mounting because it is the key to a smooth ride. When you have a tire mounted the procedure is critical and why will be explained below. Understand the procedure so if a tire technician does not follow it, insist that he redo the mounting.
First, the wheel has to be lubricated not only on the beads but the drop center. The tire needs to have the beads lubicated. The reason for the drop center to be lubed is so the lube on the tire is not wiped off prior to seating the bead using air pressure. The bead area of the tire is extremely important and lack of lubrication when seating the tire can damage it.
If a tire changer wants to change your tires without removing the wheel from the coach it is likely the tire will not be centered on the wheel so if he opts to do that make sure he understands his job is not done until the tire and wheel are centered.
After the tire is on the wheel, put the wheel on a pail or some other support so the tire bead can seat uniformly around the wheel. Seat the bead with about 5 PSI and then use a tire cage to finish airing the tire. Near the bead is a very tiny band of rubber molded into the sidewall of the tire. Before mounting the tire on the coach measure all around the tire/wheel and insure that band is equidistant from the wheel. The industry standard allowable deviation is about 5/64″ but Michelin says there is no reason why it cannot be zero. At the very least try to keep it no more than 1/32″
Why be so fussy? If the tire is not centered on the wheel you are driving on the equivalent of an eccentric. Use of the tire not centered ultimately creates wear that is going to act just liike a tire out of balance. There are industry standards for depth of tread variations and when you have them on your coach remember two things. They were caused by a tire not centered on a wheel, and once the tread depth varies you are going to feel that vibration, typically around 60 to 70 MPH and no amount of balancing will make it go away. The tire will not correct the uneven wear no matter where it is placed so the starting point for good tire service is to insure mounting is correct.
We also can have radial runout from mounting the wheel on the coach. This is especially true with hub centered wheels. There is some play between the hubs and the inner hole on the wheel. After mounting, snug up the wheel with about 3 nuts. Using a dial indicator rotate the wheel to determine if there is runout. Again if the tire is showing runout try to adjust that out. In our class at Michelin we had a truck that had about .120″ of runout on the steer axle. The tire was rotated until the greatest amount of runout was at the top, the nuts were loosened to allow the wheel to drop onto the hub and the nuts were retightened. The amount of runout was reduced from .120 down to just over .060 which was a large improvement and less than the industry limit of .080″ on steers.
A lot of bad wear on tires is not going to be noticed by those of us that put very few miles on the tires before they age out, but be assured it is going to happen and once it happens nothing will correct it, including rebalancing the tire because it is still going to be like driving on an excentric. You job as owner of the coach is to make certain you protect your investment in your tires and get the best ride out of them for the life of the tires.
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8 Replies
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Jon,
Any mention from Michelin about using Centramatics on your tires? My Bus came with them, but not sure what relevance they may have when it comes to your tires in the Mounting/Balancing area.
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Tim, none as to mntg…balancing yes…a no-brainer way to always be balanced. Geo.
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Michelin has their manufacturing so tightly controlled they did not seem to feel balancing is necessary if the tires and wheels are mounted correctly. But they do recognize balancing may be needed and while not specifically mentioning brands they are OK with balancing media or Centramatics, but did not seem especially in favor of weights. Their thoughts were that balancing using weights lacks consistency and they did a field test with tires mounted on wheels to determine if the weights were always the same amount and location. They were not the same from dealer to dealer and they found a lot of factors influenced the placement and amount of weight, with the greatest number of dealers having machines that had not been certified or recently certified.
They did mention the use of other than media, such as golf balls only to point out balancing media has its limits.
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Golf balls?!?
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Yes, golf balls. Not the first time I heard that. The media that is used should be designed for tire balancing and should have the Schrader valve with filters installed. Equal is one brand name but there are others.
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Kurt,
My truck tire dealer has clients that use four (4) golf balls per tire. I have found this successful on my 22.5 diameter tires. Not recommended by them on smaller pickup truck tires. However, I am now using Centramatics on all wheels.
Are you coming to Oysterfest? We had four Foretravels last year. I know of two coming this year. I attend this get together and skip the Foretravel ones, better time, super folks too.
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The truck tire dealer has to love the use of golf balls. Michelin made no bones about being critical of the practice because of damage to the inner liner of the tire, and when that happens the tire is ruined.
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where does a golf ball go during a blow out on a semi…..I would not want that liability….
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