Rear disc for drums on Silverado?

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by stchman, Nov 13, 2012.

  1. stchman

    stchman Active Member 2 Years 1000 Posts

    Hello all. I was reading that some people want to convert the rear drum brakes on the Silverado to disc.

    Is this a good move by GM to keep putting drum brakes on $40K pickups? I am pretty sure that the drum brakes in the rear will do the job just fine.

    IIRC GM had 4 wheel disc on their trucks up to 2002, but then went back to rear drums.
  2. Conlan Rose

    Conlan Rose Epic Member 5+ Years 1000 Posts

    Disc are great because they are easy to maintain, have superior stopping power, and work well with ABS.
    Drums are great because they are cheap, reliable, better for loads, and don't get affected by water.
    Both are great in their own way but for a daily driver disks win, for a heavy hauler drums rule. But with new disc braking tech discs are king because they can have several calipers, be easily cooler, and offer better computer control possibilities.
  3. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Disc brakes dont actually have better stopping power than drums.
    The advantages Disc's do have are:
    Shed water and debris better and faster
    Easier maintenance
    Faster cooling

    Hold water and debris out longer
    Dont have as many warping issues
    Take longer to heat up

    As far as operating force theres quite a few drum brake systems made that have multiple pressure points, but the systems used at this time dont really have the need for this type technology.

    Drums can be manufactured with more square inch's of braking force by enlarging the brake drum over the axle hub, Disc brakes require a larger disc to enlarge square inc's of braking force which means a larger wheel is required, which sometimes requires a larger brake to stop the now larger wheel, you could keep going with this until it got rediculous.

    Manufacturers have gone back to drum brake set-ups because they cost less to manufacture and have less repair issues, i.e. warping. Rotors when compared to drums tend to warp easily, and if your driving a truck designed to pull or carry heavy loads you'll be using the brakes quite a bit, after a while you'll end up warping the rotors.

    Theres a few designs manufactured to stop this issue but manufacturing cost's are more expensive.
    Take a look at many race vehicles or Semi trucks, they use Disc brakes but the disc's arent mounted at the ends of the axle inside the wheels, they're mounted inboard where they get better cooling and can be larger since their not size restricted by the wheels. But designs like this are a little cost prohibitive at this time for normal production vehicles.
  4. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    I believe all GM trucks (at least since the 1999/2000 change over have both let me explain). My 2000 silverado has 4 wheel discs with ABS.

    However the rear axle is a combination Disc/Drum where my powered brakes are discs, but the drum is there for the emergency/manual/parking brake that you press with the parking brake pedal.

    99'HEARTBEAT MODERATOR Staff Member 5+ Years ROTM Winner 1000 Posts Platinum Contributor

    The Below Article goes into Detail as to Why G.M. went back to Rear Drum Brakes, in 2005" on their Trucks,

    In Braking Systems, the Race for Better Stopping Power Is On

    Published: 16 Sep 2004
    By Avijit Ghosh
    Several automakers and major suppliers are preparing new, high-performance brake systems that can effectively address consumer concerns. Porsche, Ferrari, and Mercedes-Benz recently have launched very expensive carbon-ceramic braking systems. But automakers and suppliers are more concerned with cost-effectively improving braking systems for everyday vehicles.

    Shortcomings of Current Braking Systems:
    Chevrolet's Silverado and GMC's Sierra light-duty pickup trucks have been two of the best-selling and most-profitable vehicles for General Motors Corp. However, customers have raised certain complaints about the braking system of these models, which face stiff competition from Ford's F-150, Nissan's Titan and Dodge's Ram pickup trucks in the North American market.

    The issues that caused concern on the part of Silverado/Sierra drivers were:

    • High force must be imparted on the brake pedal to initiate vehicle stoppage.
    • The brake pedal feels spongy.
    • Brakes do not possess satisfactory stopping power.
    To address such concerns, automakers and brake system suppliers focus on the following goals:

    • Providing brakes that wear less and last longer, thus providing longer service life.
    • Reducing the force needed on the brake pedal to stop the vehicle.
    • Substantially reducing stopping time and distance.
    General Motors teamed up with brake system supplier Robert Bosch GmbH to develop a new braking system for the 2005 models of the Silverado and Sierra. This is an attempt to provide a solution to customers' concerns.

    Bosch Braking Systems:
    Bosch provides power-assisted braking systems that produce maximum deceleration even on application of relatively light brake pedal force, considerably reducing braking distance. Bosch also provides emergency valve assistance for vehicles equipped with anti-lock braking systems.
    Bosch brake pads feature multi-layer technology. They are vehicle specific, with specially formulated materials that provide high stopping power with less noise and longer service life. For light-duty full-size pickups, Bosch improved the stiffness of the front brake calipers, which reduces pedal travel and redistributes braking effort between the front and rear brakes.

    Specifics of the Bosch System for the Silverado/Sierra Vehicles:
    In 2002, Bosch received a contract from General Motors to develop a new braking system for the 2005 Chevrolet Silverado and GMC Sierra light-duty full-size pickup trucks.
    Prior to 1999, the Silverado/Sierra pickup trucks had drum brakes at the rear wheels. In 1999, standard four-wheel disc brakes were introduced for these vehicles, but these remained only through 2004. The 2005 models are reverting back to the earlier concept of drum brakes for the rear wheels.

    General Motors measures overall braking comfort and performance on a scale of 0 to 100, called the Brake Feel Index (BFI). Scores are based on a weighted composite of variables that contribute to drivers' overall impression of the braking experience. According to General Motors' estimates, the BFI of the 2005 Silverado/Sierra models will improve to 84, up from 62 for the 2004 models. In comparison, BFIs are 76 points for the 2004 F 150 Super Crew, 62 points for the 2004 Ram Quad Cab, 71 points for the 2004 Titan Crew Cab, and 59 points for the 2004 Tundra, according to General Motors.
    For General Motors, Bosch focused primarily on developing the front brakes, since pickup trucks place the majority of braking torque on the front wheels. This is mainly because during vehicle deceleration, load is transferred from the rear tires to the front ones. As the rear brakes in pickups do not significantly contribute to slowing the vehicle, it makes sense to use drum brakes, which are less powerful and less costly, for the rear wheels. Instead, developing the front brakes and other brake system components is more cost-effective.
    According to General Motors, the new braking system will reduce stopping distance by 26 meters and stopping time by 2 seconds from a speed of 97 kilometers per hour, using just the front brakes. These improvements, and the better BFI score, are attained by means of a stiffer master cylinder, stiffer twin-piston calipers, and front discs that are 2.5 centimeters larger in diameter. This reduces brake pedal effort and the spongy brake feel, and gives better overall response and proper feedback to drivers.
    The larger rotors provide an additional 355 square centimeters of swept area, which generates more stopping force. Additionally, the drums to be used are the largest in a light-duty vehicle, having a diameter of 29.5 centimeters.
    The upgrading of rotor and caliper components will allow an expensive and space-consuming booster to be eliminated. The booster had been needed to provide the necessary hydraulic pressure in the event of power loss.

    Delphi's Maximum Torque Brake System:
    Delphi Corp. has designed a braking system called the Maximum Torque Brake (MTB) system. This system uses two brake rotors for each wheel. This is an innovative concept from Delphi, because a single brake rotor has been used in every production disc-brake system to date.
    In the MTB system, each rotor is clamped by a caliper, just like in a typical single-disc system. There are four friction surfaces per wheel to generate braking force, instead of two. According to Delphi, as a result of the doubling of the friction surface area, the MTB system generates 1.7 times more braking torque as compared to a system using a single rotor with the same diameter. Stopping power is enhanced with less pedal effort. The system also incorporates low-friction linings to reduce noise.
    The twin-disc design provides four cooling surfaces, which reduces thermal stress on the brake components. This eliminates the need for vanes or cooling channels. According to Delphi, disc diameter can be reduced by 25 millimeters, which allows use of smaller, lower-cost wheels.
    This system is suitable for a wide range of vehicles, from small passenger cars to light-duty sport-utility vehicles and trucks. According to Delphi, this system can be integrated with other systems in its portfolio of electronically controlled brakes, including Delphi Electronic Stability Control. Therefore, this system may set a new standard for braking systems. However, to date, Delphi is not known to have any contracts for the MTB system.

    Will General Motors' New Braking System for Pickups Take Off?
    Market acceptance of General Motors' new braking system can only be determined in model year 2005. Although we may see technologically advanced braking systems like Delphi's MTB System in the future, these will not be able to compete on a cost basis with low-cost rear drum brakes.
    General Motors maintains that its new braking system will address consumer complaints quite effectively, but other automakers may well introduce advanced braking system of their own in the near future. The race for more-effective braking systems - both in terms of stopping power and cost-effectiveness - is on.

    Last edited: Nov 14, 2012
  6. Conlan Rose

    Conlan Rose Epic Member 5+ Years 1000 Posts

    That is my one complaint with my Tahoe it's brakes stink and feel so weak. It scares me come to a light and I just turns red because it have to try to stop 5400lb in a short distance. I wonder if old trucks can be upgraded with new brake systems?
  7. j cat

    j cat Epic Member 5+ Years 1000 Posts

    My 2000 1500 silverado has the 4 wheel disc brakes with the tiny PARK BRAKE DRUM , this vehicle has only a park brake of limited holding power. it does not have like a drum brake system an " emergency brake " , which can stop the vehicle when moving , and also to hold a heavy tow load on a grade/hill.

    these rotor vehicles had park brake recalls only on the standard shift because they lacked the proper holding power.

    rear drum brakes are best for these trucks . the rotor park brake I have is not very strong ! if you apply this rotor park brake on my vehicle with it moving this will break it. also not to hold vehicle on steep grades. this was all revealed to me after I purchased the vehicle and this was at 15,ooomi when I failed inspection because the small park brake shoes worn out due to GM defective shoe clips ! this was replaced in the stardard shift models . the automatic models got zero ! about 2yrs ago a class action lawsuit finnaly made it thew the courts GM had to pay those who could show they had to repair these defects.

    the park brake shoes worn out and never used !

    I had rear drum emergency brakes , on my prior vehicle 380,000mi and never had a failure . 15,ooomiles and the park brake went to the floor !
  8. stchman

    stchman Active Member 2 Years 1000 Posts

    The one thing I did notice about my 2013 Silverado is that the braking is way better than my 2008 Silverado. The pedal is far more responsive on the 2013 than the 2008. I gather that GM improved the brakes.
  9. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    No vehicle has this (at least, not the ones we are talking about). The parking brake is only a parking brake.
  10. Conlan Rose

    Conlan Rose Epic Member 5+ Years 1000 Posts

    Yes there are trucks that have it [MENTION=54249]RayVoy[/MENTION] the very late 90's trucks had them because they needed a better parking brake then the discs. I have several diagrams in my manual for 88-98 trucks it applies to 98's with full disc brakes most were 2wd and smaller, but it was eventually put on bigger 1500 trucks. The point is drums are better parking brakes because of their larger surface area.

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