Choosing the proper replacement and knowing when to replace brake linings is critical for performance, so manufacturers and industry organizations such as the Technology and Maintenance Council and the Society of Automotive Engineers go to great lengths to simplify the selection process when selecting replacement linings.
Common tools are friction thickness or lining thickness gauges built into a shoe or pad to enable technicians to determine at a glance how much useful life is left in the component. Many brake wear gauges have a minimum thickness check, but also have a 50% checkpoint on them. So, they not only will tell you when they need to be replaced, they also can allow you to project the remaining life left on the shoe or pad and schedule the brake maintenance for that vehicle in advance. Another point worth noting is that the majority of brake shoes are sold in kits, which typically consists of two shoes with all the applicable wheel-attaching hardware in the box so technicians will replace all of the wear components that are associated to that wheel end – such as anchor pins, springs, retaining springs and bushings – as well as check radial play in the camshaft and others items that are associated with that brake.
All quality brake shoes and pads will be marked with edge codes on the side of the friction material. These codes give crucial data about the part and help technicians ensure they are replacing it with one that offers comparable performance. Most edge codes start out, typically, by identifying the brand of the material in the pad. Naturally, the manufacturer will be noted as well. If the friction material is designed for extended service, for example, other information such as FMSI identification will follow along with mounting information that tells you if the shoe requires single or dual anchor pins. It also will have a coefficient of friction generated by the material – an alphabetical sequence designating the coefficient of friction for the lining material. Coefficient of friction can be identified as EE, FF or GG, for example. The higher the alphabet scale, the more aggressive the material.
A final piece of data on the edge code tells the batch – or specific manufacturing data – pertinent to the component. This is so that if there is a failure or performance issue with the material, it can be traced back to its manufacturing date, and even down to the exact time of the manufacturing process.
According to Hawker, the most important thing about the edge code of any friction material is the manufacturer’s name. “You need to know who manufactured that part so you know it’s being backed by somebody,” he stressed. “There are many ‘will fit,’ ‘could fit,’ ‘might fit,’ copycat and even counterfeit parts out there on the market today. One part may very well look like the one you’ve just pulled off a truck. But if there’s no name on it, I sure wouldn’t put it on a vehicle, because I wouldn’t want the liability and responsibility that I installed something that’s suspect.”