Brake upgrades for 1974 Grand Prix

[TQuillen]

Good evening -

This is my first post in the technical sections, so be gentle! LOL. I've got a 1974 Pontiac Grand Prix that I'm in the process of updating from a driver into something that can be autocrossed quite a bit, but it'll still be primarily a street car. The car currently has factory brakes, 11"x1" disc front, 9.5" drum rear. Bolt pattern is 5x4.75", wheels are currently factory 15x7, to be updated once I figure out brakes (although I'm leaning towards a 17" wheel). The car is heavy, 4300 lbs with me aboard. I'm sorta on the fence about what direction to go with the brakes. Budget is certainly a concern, but at the same time I'm not one to spend good money on the wrong parts. I'd like to do an OE based swap/upgrade if at all possible, to make replacement/maintenance parts easier to get. I've identified a couple of options that I'll list here. Please let me know your opinions, as well as any other options that I might be overlooking. If there are somewhat budget friendly aftermarket kits that will work with this car, I'm certainly all ears.

Option 1: Stock 11" fronts, upgrade to 11" drum rears and let it ride

Option 2: Stock 11" fronts, upgrade rears to S10 Blazer discs

Option 3: Convert front and rear to LS Camaro/Firebird type discs and calipers (which definitely pushes me into a 16-17" wheel)

I welcome any/all thoughts and opinions! Thanks!

Travis

[cornfedbill]

Okay, if you are not seeking to break the bank, you can swap in the complete B-body front spindles with 12" discs.

Here is the list of donor cars for B-body spindles that should fit your Grand Prix:

Buick Full Size- Le Sabre Wagon / Electra Wagon 1977-1994; Cadillac Fleetwood and Deville 1977-1984 // Brougham and Fleetwood 1985-1994; Chevy Full Size 1977-1996 Caprice, Impala, Belair, Biscayne; Olds Delta 88, Delta 88 Wagon and Olds 98 1977-1992; Pontiac Full Size Bonneville, Catalina, Grandville 1977-1986

Look for wagons, taxi cars and police cars. They typically have 12 inch discs (technically 11-3/4"). The rest have the same 11" brakes as your Grand Prix.

The issue you will have is these cars have 5X5 bolt patterns. You can redrill the rotors, or get 3rd Gen Camaro 1LE rotors. In that case you will want a later B-body spindle with the larger outer bearing. A bit of research and you should be able to find all the minute details.

This is the best budget big brake set-up around. If you want bigger brakes or something with a name brand on it, the sky is the limit. However, the B-body swap with some good street/track pads will do it.

This will give you the same size rotors as the C3 Corvettes and early C4 Corvettes on a reasonable budget.

For the rear, the S10 discs should be fine for occasional autocross events or standing mile. And you can use 15" or larger wheels as you see fit.

[TQuillen]

Thanks for that, Bill! I've read of doing the B-body spindle swap on earlier A-body cars, but not on the 73-77 cars. Any idea about ball joint compatibility? Is the B-body spindle height similar to what I have now?

[TQuillen]

Bill,

After some quick research, I found something interesting.

74 GP and 77 Impala take the SAME 11" rotors, and the 12" brake rotor uses the same inner and outer bearings as the 11" GP rotor, and is the same overall height (hat height).

Could it be this easy? I wonder if the caliper mounting bracket is the same.....

Also of note, upper and lower ball joints are the same as well.

Travis

[TQuillen]

After researching some more, it ain't quite that easy LOL. I'd like to use the 1LE rotors, so I need to find some B-body brakes with the big outer bearing. The ball joints are the same with those too. So, calipers, rotors, spindles, bearings and seals, and I should be good to go for the front. Then I'll address the rear.

Thanks again for the help!!

Travis

[cornfedbill]

After researching some more, it ain't quite that easy LOL. I'd like to use the 1LE rotors, so I need to find some B-body brakes with the big outer bearing. The ball joints are the same with those too. So, calipers, rotors, spindles, bearings and seals, and I should be good to go for the front. Then I'll address the rear.

Thanks again for the help!!

Travis

You're welcome. You chose a pretty good platform to begin with. It looks like you found the details you need for the B-body 12" brake swap. It really is quite easy for your car.

Because these calipers are very common, you can get just about any pad compound you would like. I bought Hawk pads. There are others out there. I chose Hawk because of the selection they offer.

[andrewb70]

The 73-77 A bodies use the same front suspension as a second gen F-body, and all use the same spindle as the B Body.

Andrew

[eville]

Holy **** you still have Steve Jobs? Welcome to the forum Travis.

[cornfedbill]

The 73-77 A bodies use the same front suspension as a second gen F-body, and all use the same spindle as the B Body.

Andrew

That is something I did not know. That is good information.

[TQuillen]

Holy **** you still have Steve Jobs? Welcome to the forum Travis.


Hahaha!! I sure do. I LOVE this car. I’ve been working on it but by bit, as time will allow. I don’t want a drag car.....I want something different. It’s such a neat piece to begin with, and it rides and drives really well. Thanks for the welcome, I can tell already that I like it here!!

[Skip Fix]

http://www.speedwaymotors.com/1988-92-Camaro-1LE-12-Inch-Brake-Rotor,52138.html
1LE rotors 7/16 studs

[TQuillen]

http://www.speedwaymotors.com/1988-92-Camaro-1LE-12-Inch-Brake-Rotor,52138.html
1LE rotors 7/16 studs

I looked at that option first. The issue isnt the rotors, it's finding the spindles to use the 12" rotors. These things are running for $250/pair on Ebay, and there are none around here in the yards (lots of the big cars around here went to the crusher when the scrap prices were high).

So, at this point, I'm looking at a 13" or 14" rotor conversion. It's going to be a little different than the Corvette conversions, but it looks like it's going to work well, and not cost any more than the 1LE conversion. Wish I had the coin to do a Wilwood or Baer kit, but that's not in the cards right now.

TQ

[andrewb70]

Those rotors should bolt right up to your spindles.

Andrew

[TQuillen]

Those rotors should bolt right up to your spindles.

Andrew

There are two issues: the 12" rotors (1LE included) uses a SET3 sized bearing (.844" outer bearing spindle diameter). Mine are the same as the 73-77 intermediates, in that they are the SET2 sized bearing (.750" outer bearing spindle diameter). The other issue is that the caliper mounting location is different, since my spindles are for a 11" rotor. The 73-77 rotors are like the 70-81 Camaro rotors in that the caliper mount is integral to the spindle, which makes the spindle specific to rotor diameter.

[andrewb70]

Have you looked at the Belltech dropped B body spindle?

[TQuillen]

Have you looked at the Belltech dropped B body spindle?

Yes. the dropped spindle works, but limits you on backspacing. I'm likely going to go with somewhere around a 5" backspace in the front, and the wheel gets into the tie rod end/knuckle with the dropped spindle.

Not a big deal. I've got some trial parts on the way to try something that should give me the things I'm looking for.

[cornfedbill]

Take a look here: http://www.kore3.com/

[andrewb70]

Yes. the dropped spindle works, but limits you on backspacing. I'm likely going to go with somewhere around a 5" backspace in the front, and the wheel gets into the tie rod end/knuckle with the dropped spindle.

Not a big deal. I've got some trial parts on the way to try something that should give me the things I'm looking for.

I had Belltech spindles on my GTO when I first built it and did not have issues clearing the tie rods with 18" wheels.

Andrew

[TQuillen]

Did you use the B-body dropped spindles?

Belltech specifically states in their instructions that the dropped B-body spindle is for use with a factory Roadmaster or Impala wheel, and not an SS wheel. The SS wheel is a 17x8.5: wheel with a 4.75" backspacing. I'm planning on a 18x9 wheel, most likely with a 5" backspacing.

I understand that your GTO didn't have issues, but there is a small difference in steering arm/tie rod end location on a 73-77 car vs a 68-72 car. When combined with the 2" drop and a big backspace wheel, it makes for an unworkable solution.

I've got some stuff coming for trial fitting that will likely solve a lot of my issues.

Also, if I was going to have to spend $410 on spindles, $158 on rotors, plus bearings and pads to have a 12" rotor and a single piston caliper, I'd just save a bit more for the Kore3 kit and get the benefit of a better caliper and a 13" or 14" rotor. It would make more sense, really.

TQ

[andrewb70]

Did you use the B-body dropped spindles?

Belltech specifically states in their instructions that the dropped B-body spindle is for use with a factory Roadmaster or Impala wheel, and not an SS wheel. The SS wheel is a 17x8.5: wheel with a 4.75" backspacing. I'm planning on a 18x9 wheel, most likely with a 5" backspacing.

I understand that your GTO didn't have issues, but there is a small difference in steering arm/tie rod end location on a 73-77 car vs a 68-72 car. When combined with the 2" drop and a big backspace wheel, it makes for an unworkable solution.

I've got some stuff coming for trial fitting that will likely solve a lot of my issues.

Also, if I was going to have to spend $410 on spindles, $158 on rotors, plus bearings and pads to have a 12" rotor and a single piston caliper, I'd just save a bit more for the Kore3 kit and get the benefit of a better caliper and a 13" or 14" rotor. It would make more sense, really.

TQ

I definitely had the Belltech dropped spindles. The brake package was custom made using Coleman hubs and Wilwood calipers and 14" Coleman rotors and Wilwood hats. My wheels at the time we 18x8 with I think 5" of 5.5" of backspacing. All this was 18 years ago! Damn...

I think the Kore3 solution is a good one if the budget allows it.

Andrew

[Skip Fix]

There are hybrid bearings for the outer that would allow the 12" 1LE rotor to go on an early spindle but the caliper location on the integral cast bolt holes only spaces the caliper out for the smaller rotor.

I thought I saw somewhere someone found a supply of the 12" spindles. I bought 2 sets from GM a couple of years ago used on on the '81.

Also a dual piston Wilwood D52 caliper will bolt up in place of the single.

[cornfedbill]

Also a dual piston Wilwood D52 caliper will bolt up in place of the single.

I used '74 C10 calipers because they have 2-15/16" pistons - and they are cheap and easy to find. They fit the large 1-1/4" thick 12" GM rotors.

[badbu68]

I have the whole 12" B body spindle brake setup brand new on my 68 chevelle. I sent you a pm.

[TQuillen]

I used '74 C10 calipers because they have 2-15/16" pistons - and they are cheap and easy to find. They fit the large 1-1/4" thick 12" GM rotors.

Bill - is there a 12" rotor that uses the SET6/SET3 bearing combination that is 1.25" thick? I thought the only 12" diameter 1.25" thick rotors were the truck rotors?

C3 Corvette, maybe?

[cornfedbill]

Bill - is there a 12" rotor that uses the SET6/SET3 bearing combination that is 1.25" thick? I thought the only 12" diameter 1.25" thick rotors were the truck rotors?

C3 Corvette, maybe?

The C3 Corvette rotors are the right size. That's what I have. Only issue is they do not have a hub. I used drum brake hubs. I've heard of people cutting the rotor off the center to get the proper hub to mount a rotor.

I cannot answer the bearing question. I have not had to cross that bridge.

[Skip Fix]

1980 C10 uses those bearings for the front rotor. Not sure if the width between them is the same as the B body spindles take.