From the brake pad to the shock absorber, every product that you come in contact with at a shop has a history that goes back at least 75 years. We will look at different product categories and track the innovations that have shaped these products and the future for these segments.
In the earliest days of the automobile, wheel alignment wasn’t the exact science it has become today. A measuring tape and a couple of yard sticks was about all that was needed to make sure the wheels were straight.
As vehicles got heavier and racked up more miles, tire wear and handling became much more important. Mechanical alignment gauges and sticks were developed for checking camber, caster and toe on the front wheels. Rear wheel alignment was not an issue until the arrival of front-wheel drive and independent rear suspensions. Today, four-wheel alignment is virtually a must for most late-model vehicles whether they are front-, rear- or all-wheel drive.
Time has always been money when it comes to aligning vehicles, so over the years the equipment has gotten more sophisticated and easier to use. In the early days, alignment heads were often aligned to each other with strings, sticks or optical sights. Then came lasers, sonar and infrared. Cables that connected the alignment heads to the alignment computer were eventually replaced with wireless electronic or infrared links.
Until recently, one thing most alignment machines had in common was alignment heads that attached to the wheels. The heads were often heavy, bulky and easily damaged if they were dropped or fell off of a wheel. They also required a compensation procedure to account for runout in the wheels. Then came state-of-the-art optical alignment systems that used only a simple, lightweight target mounted on each of the wheels. This made alignments faster and easier, and reduced the risk of damaging the equipment.
The latest advancement that was recently revealed at AAPEX is an automated alignment machine that finds the wheels, attaches a head and takes the measurements without human intervention! A technician still has to make the adjustments on the vehicle if alignment corrections are needed, but this shows just how far service equipment has come over the years.
The level of skill required to align a vehicle today is also much less than it once was thanks to computers. The machine prompts the operator and tells him what to do, then it measures all the angles, compares the numbers to its own internal electronic database and displays the results. The operator can tell at a glance if the wheels are out of alignment. He doesn’t have to fumble through manuals or reference books in search of the specifications. And if he needs help with the suspension adjustments, he can even look up the adjustment procedure on his machine if it has “just in time” video training modules.
Alignment machines have also become merchandising tools. The colorful displays and easy-to-understand graphics allow customers to see for themselves that adjustments or repairs are needed.
In the early days of the automobile, suspensions were often undampened because vehicles were light and speeds were slow. But as the automobile evolved, so did the suspension. The earliest means of dampening suspension gyrations was the Hartford friction shock. This was a purely mechanical device that created friction at the elbow between two arms. Tightening a bolt increased the load on a friction disk at the elbow to dampen the suspension.
In the 1920’s, the first hydraulic shock absorbers began to appear. Monroe was one of the first company’s to develop hydraulic shocks. Their early designs were single acting (control in only one direction) arm and lever units consisting of a heavy cast iron body containing a piston and hydraulic fluid. Attached to the piston was an external arm linked to the suspension with a cotton or leather strap. Later versions became two-way shocks with a metal linkage to dampen both up and down motions of the suspension.
In 1932, Hudson offered the first “direct acting” hydraulic shocks, a twin-tube design similar to those which are still used today on many vehicles. Soon Auburn, Reo, Chrysler, Packard and Terraplane were offering similar shocks. In 1949, Ford added direct acting shocks to their cars, followed by General Motors in 1950.
Direct acting twin-tube hydraulic shocks have undergone many improvements. Piston orifices and valves, and compression valves have gotten smarter to provide better control over a wider range of operating conditions. Multi-stage valving and “impact sensing” allow the dampening characteristics of the shock to change in response to body motions and road conditions.
A big advancement in shock design was gas charging. By pressurizing the shock with nitrogen gas, fluid foaming and fade could be reduced significantly for improved handling. In monotube shocks, a floating piston separates the gas charge in the top of the shock from the fluid-filled piston chamber. In twin-tube shocks, the gas charge is added gas to the outer reservoir.
Another advance was the development of adjustable shocks, first mechanically adjustable, then later electronically adjustable. Adjustable valving allows the shocks to be fine tuned to changing driving conditions. The latest innovation in adjustability is the use of “magnetic” shocks. These contain a special fluid that changes viscosity when an electric current passes through it.
The invention of MacPherson struts in 1953 added yet another dimension to the role shocks perform in the suspension. Struts are part of the suspension, not just an add-on device, so they also play a role in steering and wheel alignment.
Shocks and struts are both wear items, so don’t overlook these service opportunities when addressing ride and handling complaints.
Anti-Lock Brake Systems
Not even the reflexes of a skilled race car driver can match the performance of today’s anti-lock brake systems (ABS). Anti-lock brakes can cycle the hydraulics and prevent wheel lockup at speeds no human can match. What’s more, with stability control, advanced ABS systems can brake wheels independently to provide countersteer braking that improves vehicle stability under all driving conditions.
The notion of preventing brake lockup dates back to the 1930s when the Robert Bosch Corporation began its early development work on what would later become the world’s first electronic ABS system in 1978 on several high-end Mercedes-Benz models.
During World War II, Dunlop developed an anti-lock brake system for high performance aircraft. It was a mechanical system designed to prevent wheel skids when planes landed at high speed on slick runways. In 1958, the first practical automotive ABS system, called Maxaret, was developed by the Road Research Laboratories in Great Britain and was installed on Jensen FF sports sedans in 1966, the Ferguson P99 race car, and an experimental all-wheel drive Ford Zodiac.
In 1969, the Lincoln Continental Mark III was equipped with an Auto-Linear anti-lock unit developed by Kelsey-Hayes. Sensors on the rear wheels transmitted signals to an electronic module behind the glove box. The module controlled a vacuum-operated valve on the rear brake line to modulate pressure when anti-lock brake assist was needed.
In the late 1980s, electronic ABS systems from Bosch, Bendix, Delco, Kelsey-Hayes, Teves and others were offered on a growing number of vehicles. Most of these early ABS systems were either “rear-only” ABS for trucks (Ford RABS and GM RWAL, both of which were made by Kelsey-Hayes), or “integral” electronic ABS systems that combined the hydraulic modulator, pump and accumulator with the master cylinder into one complex and very costly assembly.
These included Delco Powermaster III, Bosch 3 ABS, Bendix 9 and 10 ABS and Teves Mark 2 ABS. These systems provided power-assisted braking in addition to anti-lock braking.
By 1994, most of the integral systems were phase out and replaced by less expensive “non-integral” or “add-on” ABS systems that used a standard master cylinder and vacuum booster with an external ABS modulator and module assembly. These next generation systems were progressively smaller, lighter and faster, and included Bosch 2, 2E, 2S and 5.3, Bendix ABX-4, LC4, 6 and Mecatronic II, Delphi ABS-VI, Kelsey-Hayes 4WAL and EBC, and Teves Mark 4 and Mark 20.
By 1990, ABS was available on about 25 percent of all new cars and trucks. Today, that figure is more than 90 percent!
As ABS continued to evolve, so did its capabilities. In the 1990s, many systems added traction control to prevent wheel spin when accelerating on slick surfaces. Then came stability control and the ability to use independent wheel braking to improve handling and driving safety under all driving conditions.
What’s next? ABS systems that use “look-ahead” sensors to detect hazards and automatically apply the brakes if the driver fails to do so in a timely manner. Some high-end Mercedes have this feature now.
In the days when drum brakes dominated the market, the finish on the inner braking surface of the drum was easy to machine. As long as the operator of the lathe did not have the cross-feed moving too fast, it was easy to cut a drum in one pass without having to do anything else to the surface. If the drum was cut too fast, the shoes were pulled away from backing plate by the corkscrew-like grooves.
When disc brakes came onto the market, machining the surfaces took on a new dimension. With drums, noise was hardly ever an issue due to the fact that drums had more mass and noise was typically trapped inside the drum. Disc brakes were lighter and the noise was out in the open. For technicians to cut a finish with a Roughness Average (RA) between 80 and 50 proved difficult on some rotors. Also, many OEMs specified that rotors have a non-directional surface. How to properly achieve this type of finish left many technicians and tool companies scratching their heads.
Many automotive tool companies came to the rescue in the 1970s with devices that could attach to the lathe or the vehicle and deliver a non-directional or “swirled” surface finish. Many of these tools looked like medieval torture devices and required special setup procedures that took extra time. The spinning motion of the rotor usually powered the devices, either by the lathe or the vehicle. Some of the better designs of these tools are still on the market.
The greatest leap forward for non-directional rotor finishing has come from the world of engineered abrasives. Some engineers realized that the surface of a brake rotor is no different than the surface of a cylinder wall or a body panel prepped for paint. Taking what they learned from these areas, some abrasive tool companies applied their knowledge to new brake tools.
These abrasive tools can last longer, while giving the same finish from the fist rotor to the last. Also, these tools can be attached to a drill or air-powered grinder and do not require a lengthy setup.
Brake hardware has been an essential part of brake repair since the start. It is one category of products that has had to evolve as brake systems changed from mechanical actuation to hydraulics to today’s disc brakes.
Mechanical actuation relied on a series of rods and cables to engage the shoes against the drums. These systems could be very complex and required constant manual adjustment. If the brakes were not properly adjusted, the driver could find the car near impossible to control under braking. Many owners of the Ford Model A found themselves in ditches if their systems were out of adjustment.
Just about every issue of BRAKE & FRONT END from the 1930s and 1940s included at least two articles on how to adjust a particular model’s brake system. These hardware items wore out as cables stretched, rods bent and clevis pins broke.
As the system changed to hydraulic actuation, brake hardware manufacturers had a whole new set of problems to deal with. Vehicles increased in size and performance capabilities, as did the braking systems.
The invention and wider use of the self-adjuster changed the segment. The star-adjuster was first used in 1922, but it did not catch on until a decade later. More rubber parts also entered into the inventory as boots and plugs were needed to protect the wheel cylinder.
The era of hydraulically actuated front drum brakes was a boom time for hardware manufacturers. It was a common industry practice to replace all springs and adjusters during a brake drum relining operation.
Early disc brake systems in the 1960s were usually twin opposing piston designs. These systems made by Girling, Kelsey Hayes and Delco Moraine used pins and clips to suspend the brake pad between the piston and rotor. Early systems were seen on exotic models like the Jaguar XK 120, but it was not until the mid- to late-1960s that the domestic manufacturers, like GM, started to widely use the systems on platforms like the Corvette and GTO.
The boom for the brake hardware market was the use of the floating piston caliper. These systems used a wide variety of hardware clips and springs to center the caliper over the rotor. Items like caliper slides, brackets and bushings were starting to find their way into shops’ parts inventory.
Today, hardware for rear disc brakes is a growing segment. With the increasing use of rear disc brakes with the emergency brake being mounted inside the rotor’s hat, the opportunity to sell brake hardware only increases.
Most early vehicles had mechanical brakes that were actuated by cables and rods. For the brakes to work properly, the linkage had to engage the drums with the same amount of force and at the same time. Keeping these systems functioning properly required constant adjustments by a trained mechanic.
In 1918, Malcolm and Alan Lougheed (who later changed the spelling of their name to Lockheed) installed the first hydraulic brake system on a vehicle. Their reasoning was that the hydraulic system could apply force equally and evenly.
The system used cylinders and tubes to transmit fluid pressure against brake shoes, pushing the shoes against the drums. Since the hydraulic fluid is not compressible, the force applied by the driver at the beginning of the hydraulic circuit remained the same at the end of the circuit.
The system was much more simple than the mechanical systems. Also, hydraulic brakes could be packaged well in a vehicle. In terms of maintenance, the hydraulic fluid did not flex or go out of adjustment like cables and rods. But, hydraulic brake systems required soft rubber lines that could wear out over time.
In 1921, the first passenger car to be equipped with four-wheel hydraulic brakes appeared — the Model A Duesenberg. By 1931, Chrysler, Dodge, Desoto, Plymouth, Auburn, Franklin and Graham had hydraulic brakes.
Ford did not have hydraulic brakes at the time due to the extra cost. It was not until 1939 that Ford switched to hydraulic brakes, becoming the last major manufacturer to switch to the new system.
Some of the resistance to hydraulic brakes was Lockheed’s patent enforcement that required the automakers to pay to use the system, and pay again to make replacement parts.
The greatest change in brake hydraulics has been the introduction of ABS systems. These systems take full advantage of Lougheed’s innovation.
The Evolution of Repair Information
Have you ever seen a wiring diagram for a 1929 Model A Ford? It’s one sheet of paper with a few lines on it tracing the headlights, taillight, ignition switch, starter, battery and ignition coil. By comparison, the wiring diagrams for a typical vehicle today can fill an entire manual. Add in the brake system, suspension, engine, drivetrain, emission controls, etc., and you need a stack of manuals to contain all the information. The volume of information required to diagnose and repair vehicles has grown exponentially in recent years.
The paper manuals that technicians have long relied on are becoming obsolete. Most shops can’t afford to purchase an entire set of paper manuals for each make, model and year of vehicle they service. They’re too expensive and take up too much shelf space.
To reduce the cost of publishing and distributing service information, most vehicle manufacturers have either done away with paper manuals altogether or offer their information on compact disks (CDs) or DVDs. But even these can be expensive. Aftermarket information providers such as Alldata, Chilton, Mitchell and others have long offered a more affordable alternative to purchasing literature direct from the OEMs by consolidating and condensing information where possible. But this too is changing. They are also moving away from paper manuals and offer electronic media, including subscription-based information access via the internet. The latter has become increasingly popular because it is easy to use (assuming you have a fast internet connection), and provides more current information (no need for quarterly updates).
Most technicians don’t have the time to thumb through hundreds of pages of service literature, so the ability to search electronically for information by system, symptom or year, make and model has been a huge help. This allows technicians to find TSBs and other information they may have never found “the old fashioned way.”
The issue now is information access. Vehicle manufacturers are now required to make emissions and OBD II-related service information available via the internet for a “reasonable fee” (typically $15 to $25 for one-day access). A complete list of the OEM service information websites is available from the National Automotive Service Taskforce (www.nastf.org). But this information may not include brakes, steering or suspension — all of which are closely integrated with the onboard electronics on many vehicles today.
Access to service information is a hot button issue today because it may limit the ability of the independent aftermarket to diagnose and repair late-model vehicles. Some say we need a “Right To Repair Act” to guarantee access to this kind of information. Others say not. The outcome of this debate may determine who has access to what, and for how much. So stay tuned!
Most of the early calipers on vehicles were of Girling design. This design had opposing pistons on either side of the rotor that would clamp down on rotor equally. The advantage of this design was in its simplicity. This design does not have any slides or bushings. The pads clamp with the same amount of force because hydraulic pressure equalizes between the two pistons. But, the disadvantage of this type of caliper is weight.
On the 1963 Chevrolet Corvette, four-wheel disc brakes were standard. The caliper used on the front brakes had four pistons. The advantage of this system was that more pad surface could be applied to the rotor in relationship to the caliper piston size. This system was a great leap forward compared to drum systems of the day. But, four pistons required a lot of maintenance. Also, corrosion of the piston bores was common. Rebuilders of these calipers usually had to bore out caliper bodies and insert stainless steel sleeves to save the core.
In the 1970s, the single-piston caliper we see today came into service. Sometimes called a floating caliper, the caliper body slides to equalize pad force and wear on both sides of the rotor and pads. This system is lighter and less expensive than opposing piston designs. Also, this type of caliper, used in conjunction with a quick-take up master cylinder, was able to lower rolling resistance and increase gas mileage.
In recent years, we have seen the increased usage of twin-piston floating calipers. This design can increase clamping forces while keeping brake line pressures low.
One trend that is making a comeback is the use of phenolic materials for caliper pistons. Phenolic pistons made their appearance in the 1970s in an effort to lower caliper weight and to create a thermal barrier between the pads and the brake fluid.
Phenolic pistons got a bad reputation from technicians and rebuilders for leaking and noise problems. But, new materials and manufacturing techniques are making phenolic pistons that are just as good as their metal equivalents.
In the early days of BRAKE & FRONT END, tire balancing was not a big issue. Vehicles rarely exceeded 50 mph and it was difficult to determine if it was a tire that was out of balance or if the road was uneven. Also, vehicles had a lot of mass, in the form of solid-beam axles, that could absorb just about any vibration.
Both during and after World War II, the government realized that to be able to move troops and supplies around the country, it needed to construct highways that were made for high speeds. This made drivers and vehicle manufacturers more aware of how an out-of-balance wheel could affect the driving experience.
Static balancing of wheels and tires had been around since the 1920s. The tool used to do this was known as a “bubble balancer.” This tool truly balanced in one plane — the static plane. It used nothing more than a carpenter’s bubble level that was parallel to the wheel. The technician would place weight on the edge of the rim so the air bubble in the level would indicate when the wheel assembly was balanced. You can still buy this tool today, but the limitations of this tool were quickly realized as the roads and vehicles were changing in the post-war boom of smooth roads, high speeds and independent suspensions.
The next step was the on-car strobe balancer. This tool would turn the wheel on rollers. Attached to the tool would be a strobe light. The operator would “look” for the imbalance and apply the right amount of weight so that the assembly “looked” balanced. This tool could solve static and dynamic imbalances. But, the tool required some amount of talent to use. Also, if you had a brightly-lit bay, it was hard to use. If you see an old shop sign that says, “we perform high speed balancing,” it is referring to this tool.
The next revolution came in the form of the “computerized” dynamic balancer. This tool entered into service around the mid-1960s. The tool used the same technology that gave rock ‘n roll its distinctive voice, the electric guitar. The balancer used the magnetic pickups that turned imbalances into electronic signals that could be understood by a primitive computer.
Today, balancers are still evolving. Through better sensors and software, balancers are able to do a lot more, such as measure runout in a rim and forces generated by manufacturing variances in tire sidewalls. Also, balancers are becoming “greener” by becoming more intelligent and deciding what is the most effective weight placement to minimize the amount of lead weights need to counteract static and dynamic forces.
In 1902, a patent was issued to F. W. Lanchester for a disc braking system that’s similar to what we have today. The biggest problem that Lanchester encountered with his new brake system was noise. Metal-to-metal contact between his copper linings and the metal disc caused an intense screech that sent chills through anyone within earshot.
Lanchester’s rotor was a simple metal disc, but it was the shape of the future. However, for the next half century the rotor was going to have to take a backseat to the drum due to the lack of hydraulics and weight.
Rotors offered much greater stopping performance than comparable drums, including much greater resistance to brake fade caused by heat expanding the diameter of a drum. Also, rotors recovered quickly from immersion in water.
In 1953, the Triumph TR2 was the first mass production vehicle to use a rotor in front instead of a drum. The system used a rotor that was solid. While the car did not have the power of an Austin Healy, it did have brakes that could last a lot longer without fading.
The next improvement to rotors came in the form of ventilation. With improved techniques, like lost-space and spin casting, rotor manufacturers were able to add air channels that could help dissipate heat by adding surface area. In the past 30 years, engineers have designed many fin configurations to increase cooling and solve possible noise and vibration problems.
The next big change came in the 1993, on platforms like the Dodge Intrepid and Jeep Cherokee, the engineers decided to go with a composite rotor to reduce weight.
The composite rotor used a stamped steel hat assembly that the rotor was cast around. While the rotor did improve fuel economy, it posed a problem for the aftermarket. To machine a composite rotor, it required special adaptors for the lathe. Also, some of these rotors were susceptible to runout caused by over-torquing of the lug nuts.
The future of the rotor is bright, literally. New carbon fiber and ceramic rotors are just starting to appear on exotic vehicles like the Porsche 911 and the Ferrari 430 as $4,000 to $5,000 options. These rotors will glow a bright orange under heavy braking.
Once considered an enemy of independent service shops in the automotive aftermarket, original equipment manufacturers (OEM) are making a strong effort to reach out to independent shops, offering them OEM parts and equipment and supplying shops with the marketing and point-of-sale materials needed to sell the parts.
When having their vehicles in for needed service, one phrase most vehicle owners understand is “return to like-new condition.” Vehicle manufacturers understand this and promote their parts as “genuine” or as being “original equipment.”
The last thing a technician wants to see is the vehicle he serviced earlier in the week pulling back into the service bay due to a faulty part.
Vehicle manufacturers are able to address this concern by stressing that original equipment parts are precisely engineered and designed to the specifications required by a specific make and model vehicle.
OEMs understand that quality is at the top of many technicians “wish lists” when it comes to ordering parts for their customers’ vehicles. For technicians, quality translates into premium parts that ensure the proper fit, function and performance, and eliminate comebacks.
In addition to providing independent service facilities with original equipment parts that are precision-engineered to factory specification, OEM dealers carry a large selection of parts to service their given nameplates. They are also able to provide technicians with the factory-approved service procedures needed to properly diagnose and repair specific makes and models of vehicles.
This support provided by OEMs has grown to include “OEM branded” or “OEM approved” tools that simplify the diagnosis and service process. OEMs realize that having the right parts is only part of the repair process and that technicians need the technical information and equipment needed to properly vehicles in their shops.
Some OEMs have stepped up their service offerings and have programs in place to take technicians’ parts orders and rush the needed parts straight to the technicians.
A few dollars saved is no consolation to the technician that did not use quality parts. Deviating from OEM design specifications can cause technicians headaches because using just one improper part that was not designed to OEM design specifications can affect how an entire vehicle system operates.
OEMs have also entered the performance tuning marketplace, offering parts that will enhance the performance or appearance of the original vehicle.
The demountable split rim made the pneumatic tire practical for the passenger car because you could carry a spare, which could be easily changed when you had a flat. Because punctures and blowouts to the cotton cord tires were very common, cars usually carried more than one spare. The rim tire and tube could be disassembled and the inner tube repaired with a vulcanized patch and the tire cord repaired with a boot.
My father showed me a trick that I will never forget. The trick was to assemble the rim tire and tube. There was a latch that allowed you to split the rim and reduce the diameter of the rim.
Up until the mid 1950s, passenger cars and trucks had tires and inner tubes. In 1954, Packards rolled out on tubeless tires on leak tested stamped steel wheels and the rest is history. From the 1930s to the present, passenger car tires have been mounted on drop center rims with a center hub and wires or stamped steel center.
Cast aluminum and magnesium drop center wheels started to appear in the 1950s. The drop center allowed a tire to be stretched over the bead seat of the wheel. A bead breaker and tire irons were the tools used to tear down and remount the tire. For the tire and tube, it would require special care to make sure that you didn’t pinch the tube and the valve stem was correctly positioned. The trick was to partially inflate the tube to keep it from being pinched by the tire iron.
There were a lot of blow outs when a tire would hit a rock or pothole that would break the cord allowing the tube to blow out. Rayon cord tires and the later use of nylon greatly reduced the number of blowouts.
The introduction of the safety rim and tubeless tire made it necessary to develop a machine to change and repair tires. The safety rim has a raised section in the bead seat to retain the tire to the rim. The old human-powered bead breaker didn’t have enough push to unseat the tire from the rim.
At the shop I was working at during this period, we bought a tire machine. The tube would always seat the bead of the tire to the rim. There was a lot of tugging and pushing to get a tubeless tire to seat on the rim. Today, it’s the blast of the inflator.
The future wheel and tire assembly will require a pressure monitoring systems to alert the driver that the tire is at a low pressure or flat. I don’t think there are going to be many tire busters.
Wheel bearings were first used as far back as the 1st century B.C. in wagons and chariots. They were crude by today’s standards, and were made out of wood, bronze, iron and even stone. Most were simple sleeve bearings packed with grease made from animal fat or lard, but some actually contained needle roller bearings.
In 1500, Leonardo da Vinci created designs for ball bearings. A century later, Galileo came up with the idea of putting the balls in cages so they wouldn’t rub together. In 1794, the first patent was issued for a ball bearing that incorporated these basic design elements. In 1899, the Timken Company started manufacturing tapered roller bearings, and in 1907, the self-aligning ball bearing was invented by the SKF company.
The basic purpose of wheel bearings hasn’t changed over the centuries, but designs and service procedures have. Wheel bearings are still used to reduce friction so more useable horsepower can push the vehicle down the road. The main difference today is that wheel bearings are made out of much more durable materials and are built to operate with precision tolerances. What’s more, most wheel bearings are now sealed and are built to last the life of the vehicle with no maintenance required.
Up until the mid-1980s, almost all wheel bearings were serviceable and had to be cleaned, inspected and repacked with grease every two to three years or 30,000 miles. It was a routine maintenance job that most technicians performed on a regular basis. But when front-wheel drive arrived, the front bearings were redesigned so they wouldn’t require maintenance.
Sealed bearing cartridges or hub units with sealed bearings assemblies were introduced first on the front wheels, then later on the rear wheels.
For a number of years, many FWD