By Christian P. Koop
As most fleet professionals know, the second costliest item, behind fuel, when it comes to running a fire or commercial vehicle fleet is the tires.
Proper tire management and tire selection are very important and basic tools that will save an organization untold dollars. However, in this article, I will focus on the safety aspect of inspecting tires and wheels on fire department rigs. Not only is the cost of tires a huge issue with today’s tighter budgets, but tire and wheel failure can also place your company or department at great legal risk-particularly if a tire blows out and the driver loses control and causes an accident where someone is injured or even killed as a result. Another scenario is where the wheel and tire come off because the lug nuts loosen or the wheel studs break, causing an accident. Either instance can expose your organization to legal actions in case of an accident or if the unit breaking down on an emergency call causes a delayed departmental response.
These types of failures should not happen if the technicians and operators follow proper procedures. This is such a critical safety concern that the National Fire Protection Association (NFPA) has outlined specific deficiencies for tires and wheels under NFPA 1911, Standard for the Inspection, Maintenance, Testing, and Retirement of In-Service Automotive Fire Apparatus, that requires placing the apparatus out of service (OOS) if found. The criteria for tires and wheels will be covered in this article along with maintenance and inspection tips.
Even though it seems a simple enough operation for a technician to properly install a wheel on a truck or on apparatus, wheels still come off and cause serious accidents. A few months ago, early one morning in Miami, Florida, an 18-wheeler lost the two right rear wheels on the trailer, which ended up hitting a jogger and causing serious injuries. Knowing how heavy these wheels are, it is amazing to me the jogger was not killed. It was an unlucky and unfortunate accident, particularly for the jogger, but also for the company that owns the truck. Think of the legal and financial ramifications facing this company now. I am sure many reading this have heard of similar incidents where wheels that came off a car or truck caused a catastrophic accident. Sadly, this accident and many others like it could have been prevented. An alert, properly trained driver should be able to spot the tell-tale signs that a wheel is loose and is going to come off.
Keeping tires properly inflated is an extremely important basic requirement. Failure to do so can lead to tire failure. Not only do underinflated tires waste fuel because of the higher rolling resistance, but also underinflation can cause damage to the tire because of higher temperatures created with excessive flexing of the sidewall and tread. This can lead to tread separation at highway speed, and the tire can even explode if a driver or technician unknowingly airs up a damaged tire that was operated at a low pressure. Many have been hurt over the years because tires exploded while they were being aired up. I personally have known two technicians who were injured as a result of tires exploding while they were raising the air pressure.
A good idea is to not stand directly in front of the tire that you are filling. Use a tire chuck that clamps onto the tire valve and has a built-in pressure gauge and valve you can hold several feet away and off to the side of the tire being adjusted. A tire safety video we show our technicians and tire repair staff to illustrate the explosive force of tires is very effective in getting their attention to understand the degree of danger. The video consists of an average size car tire-I believe it was a 15-inch-which was placed underneath the center of a midsized sedan. It was then remotely pressurized until it burst, at which time it instantly lifted the entire car four or five feet off the ground. Rest assured, this video has always gotten the viewers’ attention and very quickly made them realize how dangerous the explosive force a relatively small tire has. Now, think about how powerful and destructive the explosive force of a heavy-duty tire on your average rig can be!
Chapter 6 of NFPA 1911 lists the defects or deficiencies for tires and wheels that drivers and shop technicians need to look for either during daily inspection or when the unit is in the shop for scheduled maintenance or repairs. Keep in mind that these defects, if found on an in-service unit, are grounds to place the unit OOS until repaired. This is for good reason, because failure to do so can cause an accident like the one I previously mentioned. Fire apparatus are not immune to these defects and have also been involved in serious accidents as a result of tire and wheel failures.
The first item NFPA 1911 points out is that the gross axle weight rating (GAWR) for the axle cannot be greater than the load rating on the tire. This is critical, because if the weight on the axle is greater than the maximum the tire manufacturer allows, the tires will be overloaded. At best, this can lead to shortened tire life or, at worst, a blowout on the highway. Although not common, I have seen this issue during the acceptance phase of new equipment and the end result required the manufacturer to replace the axle, wheels, and tires to meet specifications. The best thing to do if unsure is to weigh the vehicle and compare the results against tire maximum load weight and GAWR. Keep in mind that NFPA 1911 requires fire apparatus to be weighed yearly. Refer to Chapter 16 under road tests and annual weight verification for more details.
NFPA 1911 also states that cuts to the tires’ sidewalls that penetrate the cord will meet OOS criteria. This is an area where I have seen much misinformation over the years. Many operators thought that simple sidewall cuts and scratches were dangerous when they never exposed or penetrated the cord. Most fire apparatus, because of how they are driven in emergencies, will quite often have tires contact curbs, causing scratches and sidewall wear. Training drivers on what to look for and to understand the different types of tire wear and defects and injuries will reduce these kinds of issues.
NFPA 1911 also spells out the safe limits a tire tread can wear down to. Front or steer axles can be no less than 4⁄32 inch and no less than 2⁄32 inch for the rear or drive axles. If you are into retreading, it is not a good idea to let tires wear below 3⁄32 inch. In my shop, we used the 4⁄32-inch standard for all axles to err on the side of safety after having found that some vehicles would slip and slide excessively during cornering in the rain. This was particularly true for rescue trucks that were very light when compared to the gross vehicle weight rating (GVWR) and were nowhere near GVWR even when fully loaded. This leads to a very narrow tire footprint or contact patch, which causes units to hydroplane much easier than those with normal size tire footprints.
A tread depth gauge is the best tool for checking tire wear. However, for those departments that do not have one readily available, an old method is to use a Lincoln penny. Many drivers know this old trick: Simply place the top of Lincoln’s head down in between the tread grooves. If you can see the top of his head, the tire is worn below 2⁄32 inch. Other deficiencies per NFPA 1911 affecting tires for which qualified technicians need to inspect and evaluate include punctures; cuts to the cord; bulges, other than normal bumps; or repairs greater than 3⁄8 inch. This includes bulges or knots in the tire tread and tread separation.
|1 An example of a tire that blew because of damage caused while it was run underinflated. It was an inside dual on a rescue truck. (Photo by author.)|
When it comes to wheels (aka rims), there are mainly two types in use today: the Budd Wheel and the hub piloted wheel of the tubeless variety. There may be some old apparatus still in service using Dayton Wheels; however, these are ancient and no longer used on modern trucks or fire apparatus. These wheels have an open center and a five-spoke hub that clamps to an open rim. They were revered by truckers of old but could be tricky to get to run true when tightening the lug nuts. These were basically phased out when the Budd Wheel was produced, which has a steel disc welded to the rim and is piloted (centered) onto the hub via the wheel stud holes. The most commonly used wheel today is the hub piloted. It is very similar to the Budd Wheel; however, it is piloted by a machined center in the wheel that fits onto a precisely machined flange on the hub. These wheels are available in painted steel and in aluminum with several different types of finishes available.
Both the Budd Wheel and hub piloted wheel can be plagued with cracking in the center disc around the stud hole area-generally because of loose lug nuts, improper lug nut torque, and even overloading. Cracking between the stud holes and elongated stud holes are also OOS criteria items per NFPA 1911. The standard does not allow for cracks in welds attaching the disc to the wheel or any stripped or damaged fasteners. Welded repairs on aluminum rims are not allowed on steer axles. Welded repairs other than disc attachment to the rim are also not permitted on steel wheels used on the front axle. If an inspection reveals rust stains around the lug nuts on steel wheels, it is an indication of loose lug nuts that will need to be checked further.
This is one reason I am not a big proponent of wheel covers because they will cover up these tell-tale signs. To check properly, the driver would need to remove them-something that in the real world is not likely to be done by the average driver. When installing wheels, the most critical steps for shop technicians to ensure the lug nuts won’t come loose, whether the wheel is a Budd Wheel or hub piloted type, are the following:
- Make sure the stud and lug nut threads are clean and not damaged or galled.
- Ensure the surface of the hub that contacts the wheel is clean and flat.
- Check the wheel holes for damage or elongation.
Using a few drops of oil on the studs will help ensure the lug nuts tighten down evenly and smoothly while tightening. Always make sure the rims are clean and that steel rims do not have excessive layers of paint. Excessive paint will crush down over time and cause the lug nuts to loosen. Tighten evenly to manufacturer specifications using a star pattern and an appropriate torque wrench. Carelessly using a ¾- or one-inch air impact socket to tighten wheels can easily overtorque the fasteners and, in the worst case, will overstretch the stud, resulting in cracked or fractured studs later. I firmly believe overtorquing is the number one cause of broken or fractured studs.
After torquing the wheels, road test the unit and recheck it on returning to the shop. Some may think this is redundant or a waste of time, but it is well worth not having a fatal accident because of a wheel that came off because of improperly tightened lug nuts. To firmly entrench the importance, it is a good idea to post signs in the shop reminding the techs that all wheels must be torqued prior to road testing and on return. A quality control program must be in place that conducts spot checks to ensure all technicians are following procedure and properly torquing all wheels.
Accidents involving wheel or tire failure that cause injuries or fatalities can be very litigious and costly. Proper training for technicians and drivers is key for preventing most of these accidents. Following manufacturer specifications and instituting proper procedures in the shop for installing tires and wheels on the equipment are also critical to reducing risk and preventing these types of accidents.
CHRISTIAN P. KOOP retired as the fleet manager for the Miami-Dade (FL) Fire Department after 35 years with Miami-Dade County and four years in the military. He has been involved in the repair and maintenance of autos, military track and wheeled vehicles, heavy equipment, and emergency response vehicles for the past 40 years. He is a member of the Fire Apparatus & Emergency Equipment Editorial Advisory Board. He has an associate degree from Central Texas College and a bachelor’s degree in public administration from Barry University and has taken course work in basic and digital electronics. He is an ASE-certified master auto/medium/heavy truck technician and master EVT apparatus and ambulance technician. He is a member of the board of directors of EVTCC and FAEVT and a technical committee member for NFPA 1071, Standard for the Emergency Vehicle Technician Professional Qualifications.