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Big Bore GM Metric 1978-88 Brake Caliper

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Big Bore GM Metric 1978-88 Brake CaliperBig Bore GM Metric 1978-88 Brake Caliper
Big Bore GM Metric 1978-88 Brake Caliper

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Q & A

What's in the Box

If you are using 1978-88 GM Metric style brake calipers your choices of piston sizes are pretty much limited to 2-1/2". This isn't bad unless you want to 'tune' your braking by using different size calipers front to rear. By using a larger 2-3/4" piston you will increase the braking force at a wheel over a wheel using a smaller piston.

Bleeder and inlet are both 10mm-1.5 inlet allowing the caliper to be used on either side. Plus, these calipers have been ground smooth to make them easier to paint.

Includes pads and hardware. Sold as EACH.

  • 20% increase in stopping power over stock calipers
  • Can used on the left and right sides
  • Extra ribs have been added internally while unnecessary weight was removed
  • Lighter, stronger, has more stopping power than OEM calipers
  • Each caliper includes:
    • brake pads
    • clips
    • slide pins
    • banjo bolt
    • washers
    • bleeder screw


  1. Can be configured to be used as left or right.
  2. Has a 2.75 inch bore.
  3. Uses the popular “154” (Chevrolet 78-88 mid size, 83-02 S10) brake pad.
  4. A direct replacement for the “4125/26” (Chevrolet 1978-88 mid size, 1983-02 S10) calipers.
  5. The slide bolt center to center spacing is 5.5"

You may also be interested in:

Banjo Brake Fitting Kit, 7/16-20 to -3 AN
                        One part number gets you all the parts needed to hook a -3 AN style line to a GM caliper. Each kit includes 2 banjo bolts, 2 banjo fittings, and 5 washers. Each kit services 2 calipers.
Speed Bleeder Bleed Screws, 3/8-24

The Speed Bleeder is a direct replacement for the bleeder assembly in your caliper. This makes brake bleeding truly a one-man operation. Simply "crack" the bleeder loose, pump the brakes, then close the bleeder. 

Sold in pairs.

Read more about bleeding brakes in our tech article, How To Bleed Your Brake Lines. 

Wilwood 120-6426 D154 GM Metric Single Piston Floater Caliper 2.38/.81
                        Aluminum caliper is completely interchangeable with stock GM caliper (racing only).
One stainless piston, 11" to 13" diameter, .810" thick rotors. 3.7 lbs. 5.5" mount center.

1/8" NPT brake line inlet.

Metric caliper is 1978 and newer style.

Wilwood Data Sheet

AFCO 7241-9001 Oversized 2-3/4 Inch GM Metric Caliper, Right Hand Side

These are based on the popular GM Metric calipers with 5-1/2" mounting centers.

  • Oversize: 6.4 lbs.
  • 10mm - 1.5 inlet

Oversized Metric Calipers:

Can be used in the rear of open wheel modifieds and street stocks racing on dirt surfaces to increase rear brake bias. Can be used on the front of open wheel modifieds and street stocks racing on pavement surfaces.

AFCO 7241-9002 Oversized 2-3/4 Inch GM Metric Caliper, Left Hand Side

These are based on the popular GM Metric calipers with 5-1/2" mounting centers.

  • Oversize: 6.4 lbs.
  • 10mm - 1.5 inlet

Oversized Metric Calipers:

Can be used in the rear of open wheel modifieds and street stocks racing on dirt surfaces to increase rear brake bias. Can be used on the front of open wheel modifieds and street stocks racing on pavement surfaces.


Wilwood 120-8924 D154 GM Metric Iron Single Piston Floater Caliper

These all new cast, not rebuilt iron calipers are bolt-on replacements for 1978 and later GM Metric calipers widely used in "spec" racing categories and low cost disc brake conversions. Not IMCA pproved.

Wilwood iron GM Metric calipers combine new part quality with modern machining precision. There are two piston size options to assist builders with properly building static bias into a car. Previously, builders using the metric calipers generally had to mount the same size calipers on all four wheels. This drastically limited the tuning options and often created front to rear bias ratios that were not conducive to good handling and stability under hard braking. Some builders, and other brake suppliers, chose to offer re-machined OE calipers to provide a bias tuning option. Unfortunately re-machining a used casting that was never designed for the larger bore size, can create real compromises in strength, reliability and performance. 

To address these needs, Wilwood has tooled up two separate castings that are fitted with either 2.75" or 2" stainless steel pistons and high temperature bore seals. Each casting is designed specific for its intended bore size. The calipers are strong and precise, without unnecessary added weight from oversized castings. The stainless steel pistons resist corrosion while helping to slow the heat transfer from the pads. The high temperature seals provide long service life when used in hard braking applications and maintain their resilience to provide positive piston retraction on release. In addition to the optional piston sizes, two models are available with slide pin vibration dampers installed to help reduce rattle and other noise. 

These calipers are the same physical size and mounting as the GM metric style of calipers. Instead of the stock 2-1/2" piston they have either 2" or 2.75" bores. This allows you to change your brake bias on a dirt car by running bigger pistons on the back and small piston on the right front. The bleeder and inlet are both 10mm-1.5 which allows you to run these calipers on either side. 

All Wilwood GM Metric calipers use the standard D154 type brake pads. 

DOT Braided Stainless Brake Hoses, 1978-88 GM, 10mm-1.5

DOT approved brake line kits include two stainless steel -3 AN brake lines with the banjo fitting installed, banjo bolts and washers, 3/8"-24 IFF frame adapter fittings and frame tabs with clips. Includes -3 AN fittings and adapters to connect them to 3/16" brake line using a 3/8"-24 IFM flare nut.

  • Stainless steel braid over Teflon® hose
  • Reduces volumetric expansion of brake lines
  • Reduces brake fade
  • Less susceptible to debris than rubber line
Rubber Front Brake Lines & Fitting Kit, 10mm-1.5

Stop guessing which banjo fittings go with which brake lines. With this kit you get two rubber front brake lines, two banjo bolts with seals, and a pair of easy to install brake line tabs and clips.

  • 15" length including fittings
  • 3/8"-24 IFF and 10mm-1.5
  • For 1978-1988 GM Calipers

Lines are 15" in length. Features 3/8"-24 IFF at the chassis fitting to accept 3/16" brake line.

Stainless Braided 19 Inch Front Brake Hoses, 10mm-1.5
                        These steel braided front brake lines are 19" overall length. They are for common 1978-1988 GM metric style calipers and include 10mm x 1.5 banjo fittings for one end and have 3/8"-24 inverted flare female on the other. Stainless steel braid significantly reduces hose expansion under pressure, which results in a firmer pedal feel versus rubber hoses.