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    1. #1
      Join Date
      Jan 2019
      Location
      Athens, AL
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      Country Flag: United States

      Brake upgrades for 1974 Grand Prix

      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

    2. #2
      Join Date
      Jun 2012
      Location
      South Lyon, MI
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      1,217
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      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.

    3. #3
      Join Date
      Jan 2019
      Location
      Athens, AL
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      38
      Country Flag: United States
      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?

    4. #4
      Join Date
      Jan 2019
      Location
      Athens, AL
      Posts
      38
      Country Flag: United States
      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

    5. #5
      Join Date
      Jan 2019
      Location
      Athens, AL
      Posts
      38
      Country Flag: United States
      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

    6. #6
      Join Date
      Jun 2012
      Location
      South Lyon, MI
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      Quote Originally Posted by TQuillen View Post
      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.

    7. #7
      Join Date
      Apr 2001
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      The City of Fountains
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      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
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    8. #8
      Join Date
      Dec 2005
      Location
      TuoCo, CA
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      992
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      Holy **** you still have Steve Jobs? Welcome to the forum Travis.
      Steve
      '68 Camaro - SBC, TKO600, 3.73 Moser 12-bolt, Speedtech, ATS-AFX, Hotchkis, Forgeline, Ron Davis and C5 brakes (Kore3), Holley Terminator TBI.
      Check it Out Here

    9. #9
      Join Date
      Jun 2012
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      South Lyon, MI
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      Quote Originally Posted by andrewb70 View Post
      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.

    10. #10
      Join Date
      Jan 2019
      Location
      Athens, AL
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      Quote Originally Posted by eville View Post
      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!!

    11. #11
      Join Date
      Jun 2006
      Location
      Katy,TX
      Posts
      1,678
      1978 Black Trans Am 455 Edelbrock heads [email protected] through mufflers on pump gas
      1981 Trans Am 400 stock type motor
      79 Camaro getting a 500" 695 hp IA2 Pontiac motor
      1965 GTO project car
      470ci/Chevy dual quad 409 604 HP 64 Impala SS project
      2004 Pulse Red GTO

    12. #12
      Join Date
      Jan 2019
      Location
      Athens, AL
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      Quote Originally Posted by Skip Fix View Post
      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

    13. #13
      Join Date
      Apr 2001
      Location
      The City of Fountains
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      Those rotors should bolt right up to your spindles.

      Andrew
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    14. #14
      Join Date
      Jan 2019
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      Athens, AL
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      Quote Originally Posted by andrewb70 View Post
      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.



    15. #15
      Join Date
      Apr 2001
      Location
      The City of Fountains
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      Have you looked at the Belltech dropped B body spindle?
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    16. #16
      Join Date
      Jan 2019
      Location
      Athens, AL
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      Quote Originally Posted by andrewb70 View Post
      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.

    17. #17
      Join Date
      Jun 2012
      Location
      South Lyon, MI
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      Take a look here: http://www.kore3.com/

    18. #18
      Join Date
      Apr 2001
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      Quote Originally Posted by TQuillen View Post
      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
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

    19. #19
      Join Date
      Jan 2019
      Location
      Athens, AL
      Posts
      38
      Country Flag: United States
      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

    20. #20
      Join Date
      Apr 2001
      Location
      The City of Fountains
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      15,971
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      Quote Originally Posted by TQuillen View Post
      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
      1970 GTO Version 3.0
      1967 Cougar build
      GM High-Tech Performance feature
      My YouTube Channel Please Subscribe!
      Instagram @projectgattago
      Dr. EFI
      I deliver what EFI promises.
      Remote Holley EFI tuning.
      Please get in touch if I can be of service.

      "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

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