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Automechanika Frankfurt 2014 Wrap Up: Photo Gallery

Aftermarket News Managing Editor Mark Phillips represented the Babcox Media team at Automechanika Frankfurt 2014. You can catch up on a lot of last week's news from the show at Aftermarket News or the Counterman Twitter account or just take a look...

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Auto Care Marketing: Price Sensitive vs. Fear Sensitive

For 2014, I changed my health care insurance from a traditional plan to a health savings account (HSA). Basically, the first $2,500 (pre-tax) of medical expenses are on me. I was confused at first, but soon found that it did have some entertainment...

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Work Smarter With Procedures, Measurement And Accountability

You’re working harder and faster today to stay ahead of the competition and boost profitability in a challenging business environment. You’re providing the highest quality repairs and top-notch customer service so that your shop’s car count...

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Audi: Vibrates at Idle

Complaint The customer says that the check engine light is on and that the vehicle vibrates at idle. Cause The customer’s complaint is confirmed, with the vehicle vibrating at idle, but the vibration was not felt at high speeds. A scan tool found...

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Step-by-Step Lexus Fuel Pump Replacement

We will use a third-generation 2006 Lexus LS430 as our case study for this fuel pump assembly replacement. First, discharge the fuel system pressure, disconnect the negative battery terminal and drain the fuel. Be sure to remove the rear seat cushion...

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Nissan: Squeak From Fuel Pump

Customer may report a squeak noise that is: • Coming from inside the vehicle; • Happens after driving for 30 minutes; • Is coming from under the vehicle or from the left rear area of the vehicle. If you confirm that a “squeak” noise...

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Midtronics Launches Informational Microsite

  Midtronics, Inc. has launched an informational microsite — or mini website — to provide customers with detailed information about the company’s newest diagnostic platform — the DSS-7000 Battery Service Diagnostic System. The microsite...

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German Tool Specialist KC Tool Announces Addition of Gedore Tools

As of August 1 KC Tool became the first certified reseller of Gedore Tools in the United States already adding more than 2,500 Gedore tools to its selection of German made tools. KC Tool plans to add an additional 6,000 Gedore Tools over the next few...

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United Stationers Expands Into Auto Aftermarket

United Stationers announced Sept. 11 that its wholly owned subsidiary, United Stationers Supply Co., signed an agreement to acquire MEDCO, a U.S. wholesaler of automotive aftermarket tools and supplies, and its affiliates including G2S Equipment de Fabrication...

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A/C Oil Service: Avoid Compressor Failure With Proper Maintenance

HVAC systems often fail because the air conditioning compressor fails. Not following the proper service procedures or compressor oil recommendations could be factors that contribute to premature compressor failure. Refrigerant Since the mid-‘90s,...

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How Ford's New Grille Shutters Control Airflow

Some new Ford vehicles feature active grille shutters — a new system that optimizes aerodynamics by using vents to control airflow through the grille to the cooling system and engine compartment. If air is required to cool the engine, the vents...

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How Engine Coolant Temperature Sensors Influence The Modern Powertrain

  Considering that roughly 1,500 or more ­different vehicle models are introduced into our domestic market each year, it’s becoming more difficult to predict how a powertrain control module (PCM) will utilize data from a particular sensor or...

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Home Brakes Twin-Piston Calipers: Are Two Pistons Better than One?

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generate more torque. More torque means more stopping power. Also, by using the floating caliper design instead of an opposing piston design, engineers are able to avoid wheel clearance issues and other robust design features of the floating caliper.

With a single-piston caliper, the footprint of pad is limited in some ways to the diameter of the piston. The diameter can only grow so large in relation to the rotor and brake pads. If the pad is too long, it flexes. When the pad flexes, it creates an uneven friction coupling on the rotor’s face. The uneven friction can create unwanted noise. If the flexing is sever enough, the friction material can separate from the backing plate. An example of this is the early Chrysler Neon. Also, there is a direct relationship between the diameter of the rotor and the diameter of the single piston caliper.

With dual- or twin-piston brake pads, the pads can be larger with even pressure distribution. A larger brake pad has several benefits. First, a larger pad will absorb more initial heat (less thermal shock). Second, a larger brake pad will have better wear characteristics and a longer life due to even pressure distribution. Third, a larger pad is able to absorb more unwanted noise and vibration because it is able to cover more of the rotor.

Another advantage is in the area of drag and fuel savings. With dual- or twin pistons, it is possible to have more aggressive piston seals that can pull back the pads more effectively after the driver removes his foot from the brake pedal.

SERVICE CONSIDERATIONS
Dual-piston calipers can be serviced in the same manner as single-piston calipers with a few exceptions.

  • Look for uneven pad wear. If the pads have tapered wear, it could mean a problem with the caliper. Tapered wear could mean that the slides are binding or that one piston could be exhort more force than the other, or both conditions could be present.

    The slides and bushings play a critical role on dual-piston calipers. If there is too much play, the caliper could rotate on the slides. This will cause uneven pad wear.

  • The pistons on dual-piston calipers may be difficult to retract. Both pistons must be pushed back at the same time and rate with special tools. If unequal force is used, it is possible to scrape the pistons against the bores. This can damage the finish and coatings on the pistons and bores. Also, it can damage the seals.

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Andrew Markel

Andrew Markel is an ASE Certified Technician and former service writer, and he brings this practical knowledge to the Brake & Front End team as editor.
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Automechanika Frankfurt 2014 Wrap Up: Photo Gallery

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