Conversion to 12" brakes

From: Richard Kwarciany (kwar at
Date: Wed, 3 Jan 1996 10:08:28

        I have the 12" brakes on my 85 MCSS, and I'm very happy with them.
The difference in stopping power is very dramatic.  The pedal feel is great
under hard braking.  No more "hard spots" or fade, and no more need to put
both feet on the brake pedal.  You will need the following parts from a 78
Caprice Station Wagon.  Other B bodies with 5" bolt pattern also work, but I
don't know the year cut-off.  All wagons had the 5" patten (12" rotors), but
not all sedans did.  Many had the 4-3/4" bolt pattern and 11" rotors.  You'd
think that 77 would be the same, but they have different bearings.

        1)      Spindles & dust covers
        2)      Calipers & bolts
        3)      inner & outer wheel bearings, bearing washers, nuts & dust caps
        4)      Wheel seals
        5)      Brake pads

        You need rotors from a 90 Camaro w/12" rotors (1LE).

        You will also need the aftermarket upper control arms for this
application, or you will end up with way too much camber.

        Full size and mid size cars take the same upper and lower ball
joints, and have the same taper on the tie-rod ends, so the parts bolt right
on.  I'm using the stock steal 15x7 SS wheels with no clearance problems.
The stock lug nuts work fine.  The swap does not significantly affect ride
height or wheel offset requirements.  The Camaro rotors are obviously just
borrowed from the full size car, since they appear to be identical castings,
and are even machined the same.  The only difference is that the Camaro
rotors are drilled for a 4-3/4" bolt pattern, and are fitted with metric studs.


Date: Thu, 04 Jan 1996 11:19:49
From: Stuart Ing (stuarti at

These cars are canidates for the parts needed for the 12" brake swap, if you
don't feel like buying all the parts new.  This comes straight from the
Global West catalog, so it sould be good.

Buick, Pontiac, or Chevy full size 1978-1992
Caddy Seville and Deville 1978-1992 execpt for limos
Olds Delta 88 coupe and Sedan 1978-1992
Buick Riveria 1977-1979

If you go the junkyard route, then make sure to actually measure the discs
as these cars also came with 11" disc.  These discs are drilled for a 5x5
bolt pattern while the monte is 5x4.75.  So, you can either get the camaro
1le discs which are the correct bolt pattern and metric studs, or get the
discs redrilled for the smaller bolt pattern.


From: Aaron B. Armendariz (zirad at
Date: Wed, 3 Jan 1996 16:43:13

These are the items needed for a Hotchkis suspension mod with the 12 inch

Bilstein shocks 
     fronts 2ea,  pn. B360949
     rears   2ea,  pn. B460929
Eibach Springs (call Hotchkis)
General Motors
    front spindle, left  1ea, pn. 14012589
    front spindle, right, 1 ea, pn. 14012590
    1LE 12-inch rotors, 2 ea, pn. 18016035
    Dustshield, left, 1 ea, pn. 344023
    Dustshield, right, 1 ea, pn. 344024
    Dustcaps, 2 ea, pn. 1400344
    Washers, 2 ea, pn. 457707
    Nuts, 2 ea, pn. 378137
    Calipar bolts, 4 ea, pn. 5463495
    Caliper, left, 1 ea, pn. 18015427
    Caliper, right, 1 ea, pn. 18015427
Wheel bearings and seals.

**Note: 70-81 camaro spindles and 11 inch rotors will also fit this car.

Hotchkis Perfomance
    upper trailing arms, 2ea, pn. hpta02
    lower trailing arms, 2 ea, pn. hpta01
    trailing arm braces, 2 ea, pn. hpbr01
    tubular upper A arms, 2 ea, pn. hpaa01
    Machined tie rod sleeves, 2ea, pn. hptr01

Make sure that you replace the stock master cylinder with ont that is
compatible with the calipers being used.  A unit from a '74 camaro fits
right in.  It fits the power booster and the brake line fittings on the
monte.  Other master cylinders will fit the booster, but be aware that later
model master cylinders require metric style fittings.

source: Car Craft June 93 "armed and dangerous"

From: George Dumpit (george at
Date: Thu, 27 Nov 1997 12:48:27 -0800

Parts list used:

Front upper control arm:.....Hotchkis (1101)
Master Cylinder:.............86'Caprice/Impala - Raybestos (39328)
Calipers:....................86'Caprice/Impala - Raybestos (RC4123-R, 
Rotors:......................F-body 1LE - Raybestos (5994)
Outer bearings:..............(A3)
Inner bearings:..............(A6)
Inner bearing seals:.........(8871)
Spindles & Back plates:......86'Impala - Salvage yard cores
Brake hoses:.................Russell DOT S/S braided hoses 
Front coil Springs:..........3rd Gen F-body - TRW (CS5662) (706 ft/lbs)

Last weekend I finally got around to doing the 12" brake conversion on
the Grim Reaper.  It was pretty much a straight forward R/R procedure.

Yes, I went with the Hotchkis upper control arms instead of the Global
West arms.  As Brian said in his post about paint shops, go with your 
instincts.  Bottom line is that GW wasn't up front with me with their
schedule and lost my business.  Since I don't do auto crosses, or any
serious canyon carving, the Hotchkis arms fit my requirements just fine.

I had purchased the Spindle/backing plate/rotor/caliper assembly from
the salvage yard a few months ago.  The only thing that I didn't use
were the rotors, because they had the 5 on 5 pattern.  Since my sister
works for the caliper manufacturing division of Raybestos, the calipers
were rebuilt for free.  The Impala/Caprice calipers are huge single 
piston calipers, in comparison to the stock single piston Monte Carlo
calipers.  I also got the 1LE rotors, and the Impala/Caprice master 
cylinder from my sister, so the prices quoted on my web bio, are about 
1/4 of retail cost.  I originally was going to go with the 1LE 
calipers, and master cylinder, but the mounting of the Dual piston
1LE calipers required the spindles from a 1LE equipped F-body, so it 
wouldn't work with the Impala/Caprice spindles that I already had.  The 
master cylinder also was different, the brake fittings were in-board, 
instead of out-board, and were different sizes.

I had painted the all of the parts prior to installation the weekend 
prior so all I had to do was the R/R last weekend.  Taking my time,
the whole R/R took most of the day.  Total work time was around 4 hours,
but quizzical neighbors and a few parts store runs, made it a day project. 

I had to R/R the coil springs twice because the car didn't sit at the
ride height that I wanted.  I initially just cut half a turn off of the 
replacement coils, which wasn't enough, so I cut a total of 1 turn off.
Total R/R just for taking off the coils, cutting them, and reinstalling 
was 1 hr. (this is with air tools)  The front end, from the ground to the 
top of the fender is 26" (27.25" rear, w/bell tech 5100 coils, 1 coil cut 

The guys at the alignment shop were totally oogling over the Reaper.. ;-)
In fact I thought that I would never get out of there.  The toe-in will
be totally off when you install the new spindles, so eye-ball them as
close as you can and then get the car aligned as soon as you complete
the R/R.  My eye balls were 2 degrees out on both sides of the car.. 8-)

Hopefully the pictures that I took of the R/R turn out.  It was kinda 
getting over cast when I was doing the upgrade, so I don't know if there 
was sufficient lighting.  I will post them as soon as I can get them back 
and scanned.

Handling/ Braking impressions:

I am thoroughly impressed with this upgrade.  The braking is awesome in
comparison with the stock setup.  The stock setup was good, but for those 
of you that have added more ponies to your cars, I highly recommend
getting your brakes upgraded also.  I still haven't installed the new
master cylinder, and I'm really impressed with the braking of the upgrade.
I don't what the differences are between the old master cylinder, and the
new master cylinder, but I will post my findings, if any as soon as I get 
the new one in.

I thought that the stiffer spring rate was going to be a little to stiff,
but it isn't any more stiffer than an F-body with stock suspension.  It's
firm, but not unbearable.  The stiffer coils, the negative camber 
characteristics of the Hotchkis tubular upper arms, after market anti-
sway bars, and the comfortable valving of the Monroe shocks, have made, 
IMHO, an awesome handling car that's very comfortable on city streets. 

The Reaper may not be able to hang the corners with Dave's and Jenni's 
Intimidator, but I know that I wouldn't be *too* far behind.. ;-)  

If you don't want your car to handle better, but don't really want to
go with a higher spring rate, I would recommend going with a replacement
spring from an S-series chevy pickup (TRW-5660) (639 ft/lbs).  According
to the How-To Section steering/suspension by Steve Orlin, the S-series 
spring will lower the vehicle somewhere between stock ride height and 1" 
from stock.

I don't know what the braking differences would be between the Baer system
and my upgrade, but dollar for dollar, the 12" Impala/Caprice conversion
is a winner!  Especially for a daily driven street car... ;-)

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