Going Back to B-Body Front Brakes

UNGN

Comic Book Super Hero
Sep 6, 2016
2,848
113
Southlake, TX
I’m getting my 1986 T-Type back on the road after 2 years of sitting. I’ll post a build thread with all of the upgrades/changes. But for this thread I’m going to go into the Pro’s/Cons of B-Body Brakes on a G-body. The T-type currently has 12" LS1 Front Brakes, that look great and all, but I can't fit my Strock T-type wheels and the GTA rears I run in front are close all over to both the Caliper and the Tie Rod.

I had the B-body brakes on my car for a while. Robert Adams, who did the Spindle ream (to allow larger screw-in Mopar ball joints) and sold the cheap conversion U-B machine Upper Control Arms (with said ball joints) was local to me in DFW back in the day. I found the 12” Spindles on a ’84 Pontiac Wagon in the Junkyard. Most B-Body sedans had 11” spindles and S-10 Blazer stuff is a much easier/better way for 11” brakes than the B-body ones.

B-Body spindles have an inherent Bump Steer problem. They are over 1” taller than the G-Body/S10 Blazer Spindles 8.7” tall Vs about 7.5” and they are like getting a tall upper & lower ball joint – so the camber curve is better with normal ball joints, but the height of the tie rod is off for normal steering geometry that makes bump steer happen that you feel in the steering wheel.

Lower, stiffer springs help reduce the bump steer (less travel, less total bump steer), but the two mods that combine to seem to practically eliminate it in normal driving are a Howe adjustable center link, lowered to just above the skid horn on the K-member and a ½” taller lower ball joint (which is like adding a 1” + another ½”) on a stock spindle. Later in the thread I will detail the changes in Camber over full suspension travel. +1” Total spindle height over stock seems to keep the static camber throughout the travel (great for drag racing), but more than +1” gives a camber curve more like a sports car (negative on compression, going towards positive on extension), opposite of the stock curve.

Though I had B-Body brakes on my car for years, I only had about 500 miles on the ideal Howe centerlink/Tall lower ball joint set up before I came across parts to complete a 12” Dual piston LS1 set up for stock spindles. Seduced by lighter Aluminum Dual Piston Calipers, I swapped away from the Cast Iron Caliper, single piston B-Body brakes. Both brakes are much better than stock, but the LS1 brakes won’t fit ANY 15” wheels and even some 16” wheels need spacers to clear the calipers. I put about 1,000 miles on the LS1 Setup and its good, but new parts availability in 2020 and good things about the B-Body set up is why I’m switching back.

To summarize:

Con’s of B-Body Brakes:
  • Heavier than stock (but then 12” brakes are usually heavier than 10.5” brakes)
  • Swap best done with conversion specific Upper Control Arms
  • Bump Steer
  • 1980’s B-Body Station wagons aren’t in every junkyard, any more
  • Bump Steer

Pro’s of B-Body Brakes:
  • Better Camber curve than stock
  • Spindle has 1/2“ shorter steering arm than stock (a little more wheel clearance, but much faster steering)
  • Integral rotor/hub/tapered bearings are more stable than 2 piece hub/rotor/sealed bearings, especially with wheel spacers.
  • 12” brakes that will fit inside some 15” wheels. LS1 12” brakes won’t fit inside many 16” wheels without spacers (see stability problem, above).
  • 3/8” wider than stock, so GTA rears and some modern backspace wheels will fit without spacers.
  • Cheap, widely available 1LE Camaro/TA 12” rotors easily get rid of the 5X5” B-body bolt pattern.
  • Huge D52 Large Metric Single Piston Caliper weigh a ton, but have tons of clamping force.
  • Wilwood has new, Aluminum, 2 Piston D52 Bolt-on Replacement Calipers, for less than $400/pr.
  • The Bump steer is fixable to levels that are not noticeable in normal driving.
Hopefully over the next few weeks I can complete this project without a bunch of other stuff coming up.

Here is a size comparison between the 12" B-Body Rotor and 10.5" stock:


Here is how the B-Body Brake looks on the car:


Here is the 12" LS1 Brakes I'm replacing. My Plan is to have B-body brakes that look this cool:


Here are My new 1LE Stop Tech Rotors that will be going on the B-Body Spindles:
 

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Last edited:

Rktpwrd

Comic Book Super Hero
Feb 2, 2015
2,957
113
Calgary, Alberta, Canada
I’ll definitely be watching with great interest, especially the bump steer parts. I’ve got the B body spindles with 14” 6 piston Wilwood calipers on The Juggernaut.
 

81cutlass

Comic Book Super Hero
Feb 16, 2009
2,686
113
Western MN
I test fit my t type wheels on my 2+2 with ls1 fronts and it fit barely. The cooling fins did need some light grinding but I swore they fit.

I took a photo but I can't find it now of course.

Regardless interested to see the route you go!
 
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UNGN

Comic Book Super Hero
Thread starter
Sep 6, 2016
2,848
113
Southlake, TX
I’ll definitely be watching with great interest, especially the bump steer parts. I’ve got the B body spindles with 14” 6 piston Wilwood calipers on The Juggernaut.

A Howe adjustable center link + 1/2" Proforged lower ball joints seems to have dialed out the majority of the bump steer. With these changes it went from noticeable to not noticeable.

I basically lowered the center link until it couldn't go any lower due to the Skid Horn. If I cut clearance the skid horn it might take a few more washers. This picture was from 2013:



The center link alone was OK. but some bump steer was still there, and I couldn't go much lower.

I bought tall proforged lower ball joints for the LS1 brake swap. So I put them on first (I was swapping in new springs). My reaction on the first drive was "hey, the bump steer is gone", then tore it all off for the LS1 brakes.
 

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UNGN

Comic Book Super Hero
Thread starter
Sep 6, 2016
2,848
113
Southlake, TX
I test fit my t type wheels on my 2+2 with ls1 fronts and it fit barely. The cooling fins did need some light grinding but I swore they fit.

I took a photo but I can't find it now of course.

Regardless interested to see the route you go!

I don't think they will fit without spacers and the LS1 brakes with spacers is super sketch. The broken stud on my LS1 brake picture was done without spacers. Wheel adapters might stabilize things, but the LS1 brakes already space the wheel out almost 3/8", so a narrow front tire is required if a spacer is used.
 
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Ribbedroof

Comic Book Super Hero
Supporting Member
Jan 4, 2009
3,692
113
Wellston, OK
I believe my 94 Roadmaster donor car had 12" discs on it, and it is my understanding that the chassis components on the B cars were essentially the same from 77-96 as far as interchange. If that is in fact the case, could make finding spindles/knuckles a little easier, as the later B bodies are somewhat more common than the earlier versions in yards around here, anyway.

Good to see your expertise back on the board
 

UNGN

Comic Book Super Hero
Thread starter
Sep 6, 2016
2,848
113
Southlake, TX
I believe my 94 Roadmaster donor car had 12" discs on it, and it is my understanding that the chassis components on the B cars were essentially the same from 77-96 as far as interchange. If that is in fact the case, could make finding spindles/knuckles a little easier, as the later B bodies are somewhat more common than the earlier versions in yards around here, anyway.

Good to see your expertise back on the board

That is a great point, Pretty much all of the 1990's B-bodies had 12" brakes, When I got my spindles in 2000, there wasn't many '90's cars in the local pick-n-pull.

Today, there isn't many 1980's cars.
 
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PBGBodyFan

Master Mechanic
Mar 3, 2009
488
93
Wisconsin
I ran the b-body spindles/brakes on my SS for about 15 years, the bumpsteer was a thing but not that horrible IMO. The braking power, with the b-body booster and MC, was and still is impressive. The C5 stuff isn’t noticeably better to be honest, as far as pure braking power.
 

pontiacgp

blank
Mar 31, 2006
29,414
113
Kitchener, Ontario
we ran B body spindles and rotors on our G body circle track to try them out vs the 2nd gen camaro set up. As far as braking the B body calipers use the same pad as the Camaro. For rotors the B body has a 5x5 so we got the rotors off a 2wd Astro which has the 5x4.75. We stuck with the Camaro set up, smaller rotor but less rotating mass and same brake pad contact area on the rotor
 

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