While it may seem like keeping your wheels on is an easy matter, you’d be surprised. Although manufacturers regularly issue manuals, procedures and bulletins regarding wheel separation, somehow wheels manage to separate from rigs at a rate of two or three per day every day across the country.
In order to ensure your tractor and wheels don’t have a messy divorce, you’ve got to make sure you are taking the right steps. Today we are going to dive into four different factors in ensuring you don’t become a victim of wheel separation.
There are a number of different wheel bearing and hub systems on the market today. Because of the variety of design, it is imperative that fleet technicians know what procedures to use when working on the bearing in question. The American Trucking Associations Recommended Practices Manual outlines this information in the RP618A section.
In the manual, it discusses the need to use dial indicators to verify bearing adjustment. Even so, using dial indicators is often cited as left out, despite being a critical part of the process. Still, some would say even getting technicians to use torque wrenches represented a huge step. Getting them to consistently use dial indicators will also take time.
Fleet technicians must also be on the lookout for incorrectly installed or LMS-type systems. If the technician doesn’t know the type of system he or she is working with, the standard procedure of torqueing down and then backing off might damage the spacer and bearings. Not all setups are conventional single- or double-nut systems.
Wheel and Hub
One of the big areas where fleet technicians miss steps is in the area of wheel and hub preparation. Always remember to ensure the contact surfaces between the hub and inner and outer wheels is completely free of any debris, including dirt, rust and grease.
When you allow foreign material to build up on the wheel-end mounting surfaces, you cause there to be extra thickness in the joint itself. This can lead to decreased tension in the bolt, which in turn can lead to a loss of clamping force. When this happens you could be looking at potential nut and/or wheel loss.
Ensure you rigorously clean all contact surfaces with a wire brush before you set about mounting the wheel. Wheel studs should also be cleaned with a wire brush. You want to make sure the thread grooves are free of rust or any other foreign material that might impact the torque on the nut.
If you live by one principle, let it be this: Tighter is not better. While many a fleet technician will try their best to achieve maximum clamping force, usually by applying force in excess of 500 ft-lbs. of torque, they are failing to take the consequences of such action into account.
Too much pressure on a wheel stud could cause it to stretch past its yielding point. If this happens, the joint will actually exhibit less clamping force. Avoid this by using a calibrated torqueing device to bring them up to their optimal torque setting. Also avoid impact guns.
Above all, remember that a stud stretches like a spring, so if you don’t apply the right amount of torque, you won’t get the proper clamp load. As it stands, over-torqueing is one of the most common mistakes made by fleet technicians.
The fact is this: Both fleet technicians and truck drivers have a role to play in keeping a watchful eye for potential problems. One example of this would be lubricant leaking from an inner wheel seal. Since it leaves oily streaks on the inside of the tire tube, this problem can be easily spotted.
Other things to look out for are abnormal tire wear, evidence of lubrication leaking or contamination, hubcap window discoloration and gasket striation.
Although fastener tightness can’t be verified without special tools, truck drivers can check for rivulets of rust appearing around the wheel stud. Nut position indicators are also available and can show the position of a nut compared to its neighbor. Movement indicates a potential problem.
Above all, one must always be on the lookout for these systems to avoid wheel separation. The last thing you want as you charge down the highway with a full load is for one of your wheels to fly off.