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The Fleet Technician’s Log: How to Evaluate Brake Linings

The Fleet Technician’s Log: How to Evaluate Brake Linings

Welcome to QuickTSI’s latest blog series, The Technician’s Log. In our Technician’s Log posts, we are going to look at complex issues facing fleet technicians, day-in and day-out. Whether it be related to the latest engine technology, how to service an AMT, or the latest trends in big rig maintenance, we are speaking directly to the men and women in the shop that make sure a motor carrier’s vital equipment stays road-ready.

In our first installment in the series, we are going to take a deep dive into a real wonky topic: Brake liners. While it may seem like a dry topic to most, for a shop technician, understanding edge markings on a brake lining material and knowing how to maintain linings are critical aspects of the job. Since edge markings indicate who made a brake liner, what it’s made of, and its coefficient of friction, this information s vital to the proper functioning of a vehicle’s brakes.

It’s About More than Stopping Distance

Buying brake linings for a heavy-duty commercial motor vehicle involves a huge range of choice. From size to color, fit, material, and style, there is no shortage of considerations. It is also important that front-line technicians evaluate the application in which the brakes will be used, the rig’s configuration, and the trade-in timeline. To be short, there are a lot of things to evaluate.

Of course, for many fleets the primary consideration is the bottom line. How high a piece of equipment costs is generally the first thing a fleet manager or procurement officer thinks about before making a bit purchasing decision. Yet, far too often motor carriers sacrifice performance to keep costs low, a most unfortunate decision.

Consider this: Eight years ago, the federal government changed the stopping distance requirement for heavy-duty commercial motor vehicles. This change resulted in approximately 80 feet being shaved off the allowed stopping distance. While manufacturers were quick to change their build requirements to accommodate this change, it is worth noting that the new regulations only apply to new vehicles off the line, not vehicles currently in service.

When it comes to existing vehicles, one need only look at 49 CSR 393.40. If you read the text carefully, you will see that the only the thing the requirement states is that vehicles must be maintained in compliance with the rules and standards that were in effect at their build date. This regulation includes brake linings and stopping distances.

The problem? The rule exists, but how do authorities enforce it? Even during an audit, it is unlikely investigators will have a log handy helping them determine stopping distances based on manufacturing date. This allows fleets to essentially do what they want, including buying cheap brake linings and smiling as they save a few pennies doing so.

Unfortunately, this is a counter-intuitive strategy. When a motor carrier invests in advanced safety technologies and systems, is it really wise to then outfit their vehicles with sub-par brake linings? If a motor carrier changes out original friction to save a buck, they could see major problems with electronic systems down the road. Investments in advanced safety technologies fly out the window when corners are cut in other areas.

If there is one area that should get any trucking company’s attention, it is this: Litigation. Do you think plaintiff’s attorneys won’t be aware of cheap brake linings result in a compromised safety system, which leads to a collision? The last thing any motor carrier wants is to find themselves in court trying to explain why their decision to outfit cheap, aftermarket brake linings led to an avoidable accident, even if the brakes had nothing to do with the accident. Good plaintiff’s attorneys zero in on any obvious indiscretion they can, and juries are inclined to listen. The motor carrier is always at a disadvantage in court.

What to Look for in a Brake Lining

Now that we have covered how important something as simple as a brake lining is, we want to offer some procurement advice. Brake linings are all about friction; they must have enough of it to effectively stop the vehicle. But they also must wear at a rate that makes them cost-effective. Cheaper varieties also may inadvertently put strain on drums and rotors.

Although an aggressive lining might decrease the vehicle’s stopping distance, it could cause damage to other brake parts. Not only do you need to consider the cost of the lining, you need to consider the cost of your drums and rotors, which are generally far more expensive. Yet, on the flipside, linings that provide less friction or focus on a quieter ride may be more short-lived or less effective.

Sure, it is important that a brake pad lasts a long time, but rarely does a rotor salesperson talk about what kind of impact their product will have on the rest of the system. Instead, they will talk up the benefits of wear performance and stopping distance. Then, when the rubber hits the road, fleets wind up with excessive heat transfer and eventual stress cracks in the rotors. Too much stress could exceed allowable limits and take the vehicle out of service. At worst, the rotor could rupture while the vehicle is in use and result in an unfortunate situation.

As with any other procurement situation, it is critical that linings and pads are purchased based on the desired application. Is your fleet running long-haul freight? There are specific brakes for that. Is your fleet running a refuse hauler or tanker? There are specific brake requirements for those applications as well.

Getting the formula right for the application is not just a matter of desire, it is a critical matter of safety and compliance. Brake lining formulas are designed for different purposes, whether it be for carrying super-heavy loads or accommodating frequent stops. Operators running in dense urban environments know this all too well, as pedestrian interaction requires quick stopping.

Making Procurement Decisions

Procurement managers are not technicians, which is why it is critical that the consult with the shop to determine what the appropriate purchasing decision is. Any technician worth their salt should know that lining and pad materials are marked with letters and numbers, which are referred to as edge codes. These codes signify:

  • The manufacturer
  • The lining material
  • The friction coefficient

Yet, the one area where edge codes offer little help is in evaluation of the lining’s overall quality. Technicians can use the lining letters to determine the friction values, but without subjecting the material to real-world testing, it is hard to evaluate things like temperature gradients, pressure, and rubbing speed. Procurement officers and technicians need to complete their due diligence on who they are buying from before actually signing the dotted line and transferring payment.

If you are buying an aftermarket product, do you recognize the name of the supplier you are purchasing from? If you are purchasing a white-box or private label pad or lining product, you are completely in the dark regarding how effective that product will be when it comes to real-world applications. You also have no idea how it was tested and what the efficacy of those tests were. A salesperson could tell you anything, but how do you know if it is the truth?

Consider that supplier test results don’t always shed light on the truth. If you are making a purchasing decision based on marketing materials alone, compliance is hard to evaluate. Are the linings and pads RSD-compliant? Furthermore, how does compliance fit in with actual performance? You cannot look at just one aspect by itself. A purchase should not be made specifically based on a dyno test result.

When a fleet is assessing RSD compliance, they must look at the vehicle in its entirety. Tire traction, ABS activity, suspension, brake system timing, should all be part of the evaluation process. If the RSD requirement is 250-feet, the brakes must perform well on a consistent basis. While a dyno test can shed light on how well the brakes perform under certain load conditions, it cannot be used to measure real-world stopping distance.

In the end, consider what is at stake when it comes to a friction material: The safety of your truck drivers and everyone around them on the road. Choosing the proper friction lining can seem like a confusing and complicated task, but with help from the shop and careful considerations, fleets can easily land on the right decision.

While it might be tempting to downgrade the brake lining spec to save some dollars, the last thing any motor carrier wants is for a decision like that to end in an accident, or worse. Even if the worst doesn’t occur, would you really want to take that chance? Truck drivers notice performance decreases, and more, maintenance shops and technicians will detect the difference over time as inferior parts wear to quickly or damage other parts of the system. Don’t find yourself in that situation. Choose wisely.

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