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Proactive National Car Care Month Plan Could Lead To More Business

As gas prices continue to drop, ­consumers will have a few more dollars in their pockets to spend on essentials, like vehicle repair and service. Getting customers to spend some of those dollars in your shop should be one of your goals this spring. With...

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Do Training, Technology And Parts Sourcing Issues Keep You Up At Night?

We often hear that the things that keep shop owners awake at night pertain to profitability, productivity, training, keeping up with technology, shop operations/expenses and parts quality/availability. This month, we hear directly from one of your...

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Top 10 Automotive Repair Shop Pet Peeves

No two days are the same for the owner of a repair shop. Every day brings its unique set of challenges to overcome, but, for the most part, the day progresses along and one day passes to the next. But, there are those occasions when certain daily activities...

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Engine Coolant Temperature Diagnostics

While old-school cooling system service often ­focused on coolant leaks and overheating engines, let’s begin thinking “new-school” by looking at modern cooling systems through the eyes of the engine coolant temperature (ECT) sensor. Coolant temperature...

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Volkswagen: Parking Indicator Sounds Off with No Obstacle

Customer complains that the parking assistance issues warning sounds for both the front and/or rear of vehicle with no obstacle in range. Water intrusion into sensor holders is causing corroded plug contacts and sensor electrical pins, which results in...

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Volkswagen: Unnecessary Electric Coolant Fan Replacements

Model: 2006 Volkswagen Jetta Sedan Customer concerns of “electric coolant fans continue to run after the ignition is switched off” are resulting in unnecessary coolant fan replacements. It is considered normal operation for the electric coolant...

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The Right Diagnostic Tools Save You From Extensive Disassembly Time

By Andrew Shulgin, Vasyl Postolovskyi and Olle Gladso Contributing Writers and Instructors at Riverland Technical and Community College in Albert Lea, MN   A frequent reason for ­customers showing up at a vehicle repair facility is...

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Know the Specs for Your Social Media Accounts

By now, we should be well past the things I heard as recently as two years ago: “Social media is just a fad,” “No one will follow a (repair) shop on Facebook” and “I don’t care what you had for dinner, and I’m sure you don’t care where...

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MAHLE Service Solutions' New R1234yf Recovery Machine Named 'Best Use Of Technology' At MACS 2015

The ArcticPRO ACX1280 machine from MAHLE Service Solutions received the “Best Use of Technology” new product award at the 2015 Mobile Air Conditioning Society (MACS) Worldwide Trade Show. The award was selected by an impartial panel of automotive...

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Ford: Smoke From Vehicle When Starting

Vehicle: 2005 Ford Taurus SE, 3.0L Complaint: The customer says smoke comes from vehicle when starting. Cause: Confirmed the customer’s complaint and found smoke coming from the vehicle when the engine was started. Inspected the vehicle and found...

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R-1234yf Safety Procedure Checklist

Remember that R-1234yf is only mildly flammable. To become flammable, the mixture of air and refrigerant in a closed area like a vehicle cabin would need to be between 6.5% and 12.3% of the chemical vapor. This mixture must then experience a significant...

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Refrigerant Revolution: What R-1234yf Means for Service, Equipment, Safety

The new R-1234yf refrigerant is more than just a new jumble of numbers and letters on a label. For your shop, R-1234yf means several new procedures, a certification and new equipment in order to properly handle these new systems. Why the difference...

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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.

Latest posts by Andrew Markel (see all)

  • anthony daurnhime

    yeah 2 is always better then 1

    • Danny

      Sure thing

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