F-Body Caliper and 12” Rotor Upgrade

 

Written by Dick Yaeger, member, SCACGP

 

This document is not a step-by-step tutorial on installing 12” brakes.  There is another document in the upgrades section that covers that and Mike N. did a great job.

 

The reason for the upgrade is that the F-Body is equipped with aluminum dual-piston calipers, while the W-Body uses cast iron, single-piston calipers.  Is there a weight savings?  Sort of!  You will save 4.5 lb. per caliper, however you will gain 3.1 lb. per rotor when going to a larger rotor.  Total weight savings is 1.4 lb per side, but the 3.1 lb. is in rotating mass.  The other advantage is that the F-Body uses a larger brake pad (SEE Picture at bottom).  This combined with the larger rotor will result in better hard braking.

 

This document can be used in conjunction with the other document and hopefully it will help you get everything together before you start the change over, so you can be driving your car about an hour or two after you start.

 

The easy way to make this upgrade is to get a set from a wrecking yard complete.  If that is not possible, or you just want all new parts, here is what you will need:

 

2                      F-Body Calipers L&R                          18042491

                                                                                    18042492

 

2                      F-Body Caliper Brackets                      18026163

 

4                      F-Body Caliper Pins                             12530697

 

4                      F-Body Caliper Pin Boots                    12530703

 

4                      Bracket Bolts – GP                              18023729

 

2                      F-Body Caliper Banjo Bolts                 22163795

 

4                      Crush Washers – GP                            10139097

 

4                      F-Body Caliper Pin Bolts                      18026164 

Shipped with new Calipers

 

4                      F-Body Brake Pad Retainers                18026153

Shipped with new Brackets

 

The brackets need to be drilled out to accept the GP mounting bolts.  The GP bolts are 14mm while the F-Body are 12mm.  I took mine to the local NAPA store and had them drilled and tapped to 14 x 2 mm.  The charge was $24.00.  Be prepared, not all machine shops carry a 14 x 2 tap.  The first machine shop I went to had a tap, but wanted $60 for the work.  I bought my own tap and took them to NAPA.  The tap cost $24.00.

 

To get started, first compress the piston into the caliper with a large C-clamp so the caliper/pad combo will come off the rotor.  Remove the brake line from the caliper and wire it to the strut to keep it from draining and making a mess.  The banjo bolt needs to stay with the GP caliper since it is the same size as the new bolt being used, but the threads are different.  If you use the banjo bolt from the GP on the aluminum caliper it will ruin the caliper immediately. 

 

Remove the two bolts holding the bracket to the knuckle.  These have 133 ft. lb. of torque applied to them so have a breaker bar handy.  Remove the entire brake caliper/bracket/pad assembly and set it aside.  Remove the rotor and put it with the caliper assembly.

 

Install the new 12” rotor and put on two lug nuts to keep it in place.      

 

Install the bracket using either the GP bolts with thread locker or new ones.  Torque these to 133 ft. lbs. Load the caliper with pins, retainers, and pads using brake quiet where applicable.  Install the caliper onto the bracket and install the pin bolts.  Torque the pin bolts to 23 ft. lb.

 

Using two new crush washers on the brake line install a new banjo bolt.  You are on your own on the torque on this.  The book calls for 41 ft. lb., but I did not feel comfortable using that much force on the aluminum caliper.  The book only calls for 40 ft. lb. on the Grand Prix cast iron calipers.

 

That’s it.  Now do the other side.  Bleed the front brake lines, or better still, it’s a good time to flush the fluid and bleed all brake lines.  Take time to bed the pads properly.  Now, go look for your favorite canyon for some spirited driving.

 

I would like to thank the following for putting this project together, researching fitment, and part numbers, donating the first caliper by using the wrong banjo bolt, and for just having the guts to be the first to try this.  I am sorry if I have missed anyone.

 

WILLS FIERO

SARASOTAGTP

RAMAIRFREAK98SS

RATRACER

PGA2B_2004

GTP DAN

BUCMEISTER

SCORPONOX

WOLFMEISTER

 

 

 

 

Here you can see the difference in pad area between the GP and the F-Body.

 

 

Here are the old and the new, side-by-side.

 

 

Here is the finished product mounted.

 

Here you can see the finished product behind a mounted wheel.