It’s been a few years since my SAE automotive forensic photography class has been offered in the Southeast—or even in the East, for that matter! Now it will be offered May 14-16, 2024 in Orlando, FL.
Anyone working in accident reconstruction, product liability cases, vehicle testing, or other forensic, evaluation, or testing investigations knows the importance of creating consistent, quality, and useful photographs. You’ll be glad to know that you can (probably) do that with the camera you already have! Just think of how much money you’ve already saved! You just need to understand and use that camera and just a few essentials such as a tripod, flash(es), and a polarizer.
In the classroom, we will learn the fundamentals of making good, consistent photographs with lots and lots of good and bad examples. We will do hands-on sessions—both indoors and out—with tripods, polarizers, night scenes, and the big one—using one or more flashes. While it will be most useful to bring your own camera gear—including flash(es) and tripod—I will bring various tripods, tripod heads, flashes, polarizers, and neutral density (ND) filters for you to evaluate during the hands-on sessions. Those will help you determine if your gear is what will serve you best, or if you need to upgrade a piece or two.
When inspecting a truck and downloading its HVEDR, it is important to document the actual tire parameters. This includes not only confirming tires sizes, but their load ranges. You must confirm that the tire sizes and load ranges match those on the safety certification label on the door jamb and in the values programmed into the HVEDR.
In its 2023 Truck Tire Data Book, Michelin summarizes the effects of different revs/mile in this Rule of Thumb: “When going from a lower Tire Revs./Mile [sic] to a higher Tire Revs./Mile, the actual vehicle speed is less than the speedometer reading. When going from a higher Tire Revs./Mile to a lower Tire Revs./Mile, the actual vehicle speed is greater than the speedometer reading.”
The revs/mile differences between load ranges in a given tire size might not be large, but they do exist—even in the same line of tires. For example, Michelin lists two 11R22.5 X Multi D tires: one load range G and the other load range H. For the load range G tire, Michelin lists the revs/mile as 496 while it lists 494 revs/mile for the load range H tire. Likewise, for the 11R22.5 Michelin X Line Energy Z tire line, the load range G revs/mile was 502 and the load range H was 503.
So just between two Michelin tire lines, there is a range of revs/mile from 494 to 503 for 11R22.5 tires. Not only that, but for one tire line, revs/mile were higher for the LRH tire than the LRG, while for the other tire line, the opposite was true.
At first it may seem that all tires of the same size would have the same revs/mile. But variations in tire construction, tread design, and tread depth can result in small variations in the actual revs/mile of a specific tire of the same size.
Tire companies determine the revs/mile from the test procedures set out in SAE Recommended Practice J1025. J1025 specifies speed (45 mph), load, inflation pressure, ambient temperature, configuration, break-in, warm up, surfaces, measurement devices, and test distances required for each test.
The four revs/mile values of the four 11R22.5 Michelin tires above weren’t far apart, but it is best to check and confirm. And even though a small difference in revs/mile may not end up being significant in your analysis, you want to confirm that the truck tires sizes and load ranges matched what was used when programming the HVEDR.
Many trucks have a variety of tire brands, sizes, load ranges, or a mixture of original and retreaded tires. In some cases, the truck may be gone or repaired, and all you have to work with is the HVEDR report itself. When you have tire variations or unknown tires, you might consider researching the ranges of any relevant tire property, like revs/mile, then running a sensitivity analysis to quantify the effect that range of values might have on any subsequent analysis involving data from the report.
Takeaways:
-1- During a truck inspection, don’t just document the tire manufacturer(s) and tire size(s), but be sure to include the tire load range(s). Compare their properties with the programmed values in the HVEDR report.
-2- If there are variations in the truck’s tires, check the various tire properties against the HVEDR programmed values.
-3- Using those tire property variations, it might be useful to perform a sensitivity analysis to quantify the effect of a range of revs/mile or other variable.
-4- To learn how to apply HVEDR data, I highly recommend SAE International class C1901 Advanced Applications of Heavy Vehicle EDR Data taught by Wes Grimes, Greg Wilcoxson, Dave Plant, and Brad Higgins: https://www.sae.org/learn/content/c1901/
SAE International has scheduled my next Photography for Accident Reconstruction, Product Liability, and Testing (C1729) class at their excellent Troy, MI facility from April 4-6, 2023: https://www.sae.org/learn/content/c1729/
It’s a great facility and is quite easy to access on W Big Beaver Rd just off I-75. It’s about 45 minutes from the Detroit airport. There are plenty of hotels and a lot of great restaurants in every price range.
The link above provides a detailed course outline. We’ll also get hands-on time to practice with exposure, flash, polarizers, tripod use, and more.
If you have any questions or would like more details, please feel free to email or call.
With live classes now returning to SAE, I’m excited to announce that my next Photography for Accident Reconstruction, Product Liability, and Testing class will be July 12-14, 2022 at Mecanica Scientific Services’s fantastic classroom facilities in Oxnard, CA. Special thanks to Mecanica’s John Steiner for hosting this class for the third time!
The class has ten major subject modules that build upon each other. We’ll explore in-depth about gear, light, camera fundamentals, settings, post-processing, and much, much more. You’ll come away not just knowing about, but actually understanding how to make better, more consistent, and more useful photographs during all your inspections and analyses, regardless of lighting conditions.
Please call or e-mail me directly if you have any questions or need more information.
It is essential to keep truck tires properly inflated so they can carry the load, wear evenly, maximize fuel mileage, and maintain their integrity. Chronic overdeflection (overinflation, underinflation, or a combination) is a common cause or contributor to tire failures.
During pre-trip inspections, the Federal Motor Carrier Safety Regulations (49 CFR §396.13) requires the driver “be satisfied that the motor vehicle is in safe operating condition.” This includes the truck’s tires . As part of that pre-trip tire inspection, a driver is trained to look for low or flat tires. But there is no requirement that the driver check the air pressure with a gauge. In fact, while going through truck driving school before getting my CDL, we never once used an air pressure gauge during our pre-trip inspection lessons, daily routines, or exams.
It would be an onerous task to require a driver to check the air pressure of all eighteen tires on a typical tractor trailer before every trip. As an alternative to a gauge, some drivers use a “tire thumper” (usually a rubber mallet or some kind of a bat) to check their tires. If a tire is inflated, the thumper would bounce right off. Striking a tire with little or no air would have no bounce back, but would respond with a flat thud. While a thumper can’t determine if a tire is properly inflated, it can let you know if a tire is flat or near flat. [Click on image to enlarge, then click back arrow to return to this post.]
Only the bottom four of these will give you an accurate truck tire inflation pressure. (Made with ZEISS Milvus 50 mm f/2 Macro lens on Nikon D850 at f/16, 1/200 sec, ISO 64. Used one Profoto B1x studio strobe with silver umbrella with diffuser on each side.)
Back in 1998, I bought the Trucker’s Toothpick & Tire Tester at the top of the photo at a truck stop just for fun. (Both the name of the product and the company are rather whimsical.) It is a weighted metal stick with a hand grip on one end and a protective cover on the other. Along with various wooden bats, it is typical of tire thumpers sold commercially. While their benefits are minimal, at least thumpers prevent a driver from starting off on a trip with a flat tire.
The three stick gauges in the middle of the photo look similar, but their dual heads are at different angles. One of them is bound to fit when the metal valve stems of either the inner or outer tire of a dual pair are bent and otherwise inaccessible. They prevent you from bleeding air out of the tire as you try to get the gauge head to seat on the valve.
Stick gauges seem tricky to read until you understand how their scale works. I’ll describe that below.
The digital pressure gauge at the bottom is the easiest to read (and photograph, if you do that—I don’t).
Here’s how to read a truck tire stick gauge. Assume you’ve just checked the air pressure of a steer axle tire and got the reading below. [Click on image to enlarge, then click back arrow to return to this post.]
Scale on truck tire inflation pressure gauge. (Made with Nikon 105 mm Micro lens on Nikon D850 at f/16, 1/200 sec, ISO 64. Used one Profoto B1x studio strobe with silver umbrella with diffuser on each side.)
At first glance, the scale might not seem to make sense with the decimals between the longest hash marks. (Gauges typically start at 10 psi, not 0 psi; anything less than 10 psi is obviously flat.)
Zooming in might help make deciphering the scale more clear. (This photo has been rotated clockwise to be oriented as you would read the scale in use.) [Click on image to enlarge, then click back arrow to return to this post.]
Rotated close-up of scale on truck tire inflation pressure gauge.(Made with Nikon 105 mm Micro lens on Nikon D850 at f/16, 1/200 sec, ISO 64. Used one Profoto B1x studio strobe with silver umbrella with diffuser on each side.)
Let’s start with the 100 psi mark. (Note that on this gauge, the 100 psi hash mark happens to intersect the second zero.) The next short hash mark down represents 102 psi. One shorter hash mark down is 104 psi. Just below that, the longer hash mark near the center of the scale represents 105 psi. The next short hash mark at the right edge below that is 106 psi. Below that, the short hash mark is 108 psi. Next is the longer hash mark for 110 psi. Using this information, you can see the inflation pressure reading above was 118 psi.
To summarize, all the hash marks along the right edge of the scale are in 2 psi increments. Half way between the decimals, the longer hash marks near the center of the scale are in 5 psi increments.
Anywhere along the scale, anytime the end of the barrel is halfway between two consecutive short hash marks, the inflation pressure is 1 psi greater than the short hash mark above it.
Takeaways:
-1- While truck tires must be properly inflated, the Federal Motor Carrier Safety Regulations do not require truck drivers to check tire inflation pressures with a gauge during their pre-trip inspections.
-2- Tire thumpers can indicate if a tire is flat or almost flat, but cannot determine the inflation pressure.
-3- Different angles of dual head inflation pressure gauges can help access bent valve stems.
-4- If using a stick gauge, make sure you accurately read the scale.
Tire pressure monitoring systems (TPMS) are required on cars, pickups, and SUVs, and can be found on some heavy trucks. A TPMS simply warns the driver that the air pressure in a tire dropped to a certain pressure, or dropped a certain percent below the programmed pressure. TPMS does not replenish the air.
Onboard tire inflation systems, which are becoming common on air-braked trucks, semi-trailers, and buses, use the onboard air system to maintain the appropriate air pressure in each tire. Truck tire inflation systems only warn a driver if a tire loses air faster than the system can replenish it.
During routine maintenance, after a tire issue, or after an accident, you will often want to check all tire inflation pressures, even if there is a tire monitoring system or an onboard inflation system. You’ll need to ensure that either type of system was working properly. That requires checking each tire pressure individually.
With either system, how to you access the valve for each tire? Below are two examples.
First is a Stemco AirBat RF tire monitoring system on the rear tandems of a three-axle truck tractor. (Click on image to enlarge, then click on back arrow to return to this post.)
Stemco AirBat RF assembled. (Made using Nikon D850 with ZEISS Milvus 50 mm macro lens and Nikon SB-910 flash.)
There are two standard metal valve caps—one for each tire of the dual. Remove these caps and use a truck tire pressure gauge as you normally would. You can also add air through these valves if required. (Click on image to enlarge, then click on back arrow to return to this post.)
Stemco AirBat RF with valve caps off. (Made using Nikon D850 with ZEISS Milvus 50 mm macro lens and Nikon SB-910 flash.)
Make sure you know which valve goes to which tire. It’s easy to do; just trace the hose back to its associated wheel.
As an example of tire inflation systems, the Meritor Tire Inflation System by P.S.I. (MTIS) is a popular system on both new and retrofitted semi-trailers. (Click on image to enlarge, then click on back arrow to return to this post.)
MTIS by P.S.I. assembled. (Made using Nikon D850 with ZEISS Milvus 50 mm macro lens and Nikon SB-910 flash.)
With MTIS, twist the knurled fitting at either end of the through tee, then use your truck tire pressure gauge on the valve at the end of each hose. Again, make sure you trace which hose goes to which tire. (Click on image to enlarge, then click on back arrow to return to this post.)
MTIS by P.S.I. valve stem. (Made using Nikon D850 with ZEISS Milvus 50 mm macro lens and Nikon SB-910 flash.)
While these systems initially look intimidating, it is actually much easier to check tire inflation pressures with them than it is trying to get a tire gauge to fit on individual valve stems on the wheels.
I’m sure you’ve seen many photos like the one below. [Click on image to enlarge, then click back arrow to return to this post.]
Left front of truck with bad composition. (Nikon D850 with ZEISS Milvus 50 mm f/2 macro lens and Nikon SB-910 fill flash.)
What is the subject? The tire and wheel? The intruding part at the upper right (which was actually from an unrelated truck)? The gravel? Is there something important that I should be seeing in the gravel?
It was actually the tire and wheel. But if you draw a vertical line down the middle of the photo, almost the entire right half of it is unrelated to the subject.
In the image below, the tire and wheel are still featured, but now you can see how they relate to part of the truck’s frame rail and steering system, too. [Click on image to enlarge, then click back arrow to return to this post.]
Left front of truck with good composition. (Nikon D850 with ZEISS Milvus 50 mm f/2 macro lens and Nikon SB-910 fill flash.)
This photo makes more sense and eliminates unnecessary and confusing elements. It’s easy to pay so much attention to your subject that you forget what it looks like in the frame. Make sure you haven’t included too much empty space or too many unrelated elements that are not only distracting and confusing, but look sloppy, careless, and unprofessional.
From August 12 through 14, 2019, I will be teaching the third Photography for Accident Reconstruction, Product Liability, and Testing class for SAE. This time it will be at Southeast Toyota Technical Center in Jacksonville, FL. We’ll cover a lot of material in the three days, and you’ll come away making better quality, more professional photographs from that point on, regardless of the location or lighting conditions. After all, your photographs are at least as important as any other part of your work. You’re a professional, and your photographs should reflect that professionalism. After this class, they will.
While working so intensely together to conduct testing for publication, it is worth taking the time to make photographs of all those who participated. The photos can be useful for a report, any paper presentations, and the websites of the participants. (Click on image below to enlarge, then click on back arrow to return.)
Three testing partners with tractor trailer (ZEISS 50 mm f/2 macro lens on Nikon D810.)
From left to right are truck and truck ECM guru Greg Wilcoxson (Wilcoxson Consulting, LLC), truck, data acquisition, and, well, everything else guru Wes Grimes (Wes Grimes, Collision Engineering Associates), and me. In an earlier post, you’ll find a link to the papers we wrote together from this testing.
Even with my hat, I was hardly in their league. We did have fun in the evenings when I would walk into a restaurant first, and tell the hostess or host that I was their bodyguard, and needed to get them a good table. We should have recorded their reactions.
A photograph of something as long as a tractor trailer is often best presented in a panoramic format (much wider than tall). This focuses attention on the subject by eliminating excessive sky and foreground.
About half the truck wheels sold today are aluminum rather than steel. As with anything, there are trade-offs when comparing steel and aluminum wheels. Aluminum wheels weigh less but cost more than steel wheels. Aluminum wheels don’t rust, of course, but they can suffer from flange wear. Alcoa recommends checking for excessive flange wear using a simple go-no go gauge (Part No. 000700).Alcoa Rim Wear Gauge Go-No Go. (From 2015 Alcoa Wheel Service Manual.)Here’s a photograph of the gauge in use. (Click on image to enlarge, then click on back arrow to return.)Alcoa Rim Wear Gauge on rim flange. (Made with ZEISS Milvus 50 mm macro lens on Nikon D850 with flashes.)While the gauge is quite easy to use, it is more challenging to photograph. It can be tricky to hold the thin aluminum gauge in the proper position while also making a photograph. To make the photograph above, I used a Wimberley The Plamp II with one end clamped on the wheel center hole, and the other end clamped to the gauge.Using Wimberley The Plamp II to hold Alcoa Rim Wear Gauge in place for photography, with flash. (Made with ZEISS Milvus 50 mm macro lens on Nikon D850 with flashes.)The Plamp II is fantastic since it is flexible enough to get into any position, yet stiff enough to remain in place once released. Here’s a link on B&H: Wimberley The Plamp II from B&H. The Plamp II allowed me to quickly and steadily hold the Alcoa gauge perpendicular to the rim and properly up against the flange. It was easy to focus and shoot without any motion from trying to hold the gauge by hand. It also allowed me to get the flashes into position with no shadows from my arm across the photo.
If you need to photograph something like a gauge or ruler, it is worth taking the few minutes to secure it and light it properly. You can often just tape it in place, but that wouldn’t have worked to position this flange wear gauge.
