"A" body disc brake conversion

Discussion in 'The whoa and the sway.' started by Brandon Cocola, Aug 16, 2019.

  1. Brandon Cocola

    Brandon Cocola Well-Known Member

    The options are nearly endless for adapting disc brakes to the front of your Chevelle or El Camino. Much consideration must be given to your budget, your intentions for how you’ll use the car, and of course your safety when dealing with your brakes. Most of our Chevelles would have came from the factory with drum brakes, with the exception of some ‘67-72s that had optional discs and all ‘69-72 SS cars, which came standard with discs. Many of them have been converted, either using original parts, kits, or some of the other popular swaps. Each option has advantages and disadvantages. Hopefully this information will help you decide which setup is right for your car. The most important part of this is choosing your spindles.

    Stock Disc Spindles: GM was good at making things interchangeable, and the front spindles were no exception. There are several cars you can look for when searching for these spindles, and they are a direct swap onto any ’64-72 Chevelle. You can find them on 67-72 GM A-bodies (Chevelle, Monte Carlo, El Camino, Skylark, GS, LeMans, GTO, Cutlass, 442). They were also used on GM’s 67-69 F-body (Camaro, Firebird) and ‘68-74 X-body (Nova, Omega, Ventura, Apollo). 1967 was the first year for the factory disc brakes, and along with the ‘68s, they used the very rare four-piston calipers. These are very expensive to rebuild, and are worth much more to someone looking for “correct” 67-68 discs than to anyone just looking to stop well. For this reason, it is recommended to use the ‘69 and later single-piston calipers. The 11” discs are sufficient for stopping your Chevelle for ordinary type driving, but they will get hot and fade quickly if you do any road-course racing.

    Stock Drum Spindles: These are good for more than just scrap iron, so don’t throw them out just yet. With a little machining, you can bolt the stock disc caliper brackets on them, and “convert” them to disc spindles for about $80 if you can do the machine-work yourself. The drum spindles are also very popular for modifying to fit 12” C4 and 13” C5 Corvette brakes. There is some minor machining to be done on the upper bolt boss, custom caliper brackets need to be fabricated, and the Corvette rotors slip on over the drum brake hubs. Access to a machine-shop is helpful, but there have been many “do-it-yourself’ers” who have made their own brackets using 5/16” thick flat steel.

    S-10 and G-body Spindles: The brakes from 2-wheel-drive S-10s and S-15s and the G-bodies (Monte Carlo, Malibu, Regal, etc.) of the 80s are somewhat popular for converting drum brake Chevelles to discs. They are basically a direct swap, except for the lower ball-joint, which requires machining to fit the Chevelle lower A-arms. This swap is not recommended for heavy street-use, because the rotors are only 10” diameter. This is not sufficient to safely stop your heavy Chevelle in traffic. The drag racers like this swap, because the small rotors are light, and reduce rotating mass. Drag racing doesn’t require heavy braking, so this is fine for this purpose. The conversion is simple, as you simply use the ball-joints, calipers, rotors, and tie-rod ends from the donor-car.

    “Tall” Spindles: This topic always creates controversy. Some guys love them, and others equate them to the anti-christ. There are positives and negatives, but overall it’s an affordable mild performance upgrade, with parts that are easy to find. The positive aspects of this spindle come from the option of upgrading to 12” rotors, and it’s height, which changes the geometry favorably by increasing negative camber gains in compression, giving the tires more bite to the pavement. The stock Chevelle spindles are 2” shorter, and actually create positive camber in compression, causing only the outer edge of the tire to bite the pavement. The negative effects from this spindle are spawned entirely from the steering arm location, which creates bump-steer issues much worse than the stock spindles. The length of the steering arm will also make your turning radius wider, and slow your turning ratio. These spindles will lower your car about 3/4” from stock, and widen your track-width, so larger backspacing wheels may be needed for fender clearance. Aftermarket upper control arms, or offset cross-shafts will be necessary for a proper alignment. The offset shafts are much cheaper, but some people have clearance issues with them, especially on big-block ‘64-67 Chevelles with headers.

    The choices for donors of “tall” spindles are determined by what size brakes you want, 11” or 12”. The ‘73-77 Chevelles have a tall spindle that uses an 11” brake with a 4-3/4” bolt circle. ‘77-’90 Caprice (civilian) sedans also had 11” rotors and 4-3/4” bolt circle, however the ‘77-90 Caprice police-package cars and station wagons, and all ‘91-96 caprices used 12” rotors and a 5” bolt circle. To adapt to a 4-3/4” bolt-circle, you can use the 1LE police package ‘89 Camaro rotors. The ‘77 model year spindles will not work because the outer bearing was smaller, and will not fit with the 1LE rotors, and the late-95 and all 96 spindles have a 5/8” lower ball-joint rather than a 9/16”, so for this swap it is recommended that you use ‘78-94 Caprice 12” brake spindles. If you are doing this swap, it’s worth the extra money to upgrade to the 12” rotors because their larger size allows them to absorb more heat, the increased surface area helps to dissipate the heat more quickly, and the extra leverage allows more stopping power with less effort. The 12” B-body brakes are the largest brakes that will fit inside a 15” wheel. To adapt the B-body spindles, you use the B-body calipers, bearings, and ball-joints, G-body tie-rod ends, and the Camaro 1LE rotors. The lower ball joints need to be machined to fit the chevelle arms. The wheel studs are metric, so metric lug-nuts, or changing the studs will be necessary.

    Aftermarket Spindles: There are several companies selling replacement OEM style spindles, and 2” drop spindles. There are also a few companies with better options in the works. Fatman Fabrications (www.fatmanfab.com) is working on a 2” drop “Tall” spindle that uses the stock Chevelle steering arms, so you get the advantages of both the stock steering geometry, and the improved camber-curve of the tall-spindles. ATS (www.t56kit.com) is making an aluminum spindle that uses C5 corvette hubs, with optimized geometry similar to the Fatman spindles. Both of these new spindles are currently in the engineering and testing phase, and have not been released for sale at this time. [They will be available very soon -DK 11/03/05]

    Tall Ball-Joints: While using your short OEM spindles, adding Howe Precision “tall” ball-joints from Savitske Classic & Custom (www.scandc.com), will effectively add height to the spindle. You can run tall uppers for slight improvements, or tall upper and lowers for more dramatic improvements. You will achieve all the benefits of the tall spindles with none of the drawbacks, and your options for adapting larger Corvette brakes still apply. When using the lower tall ball joints, you will lower your car 3/4” and decrease bump-steer.

    I’m no brake expert, most of this information was researched here while I changed my plan daily, and had to keep researching new options. I have officially decided to use OEM spindles, with stock 11” brakes, until my budget allows for 17” wheels to clear the C5 13” Corvette brakes I really want.

    So I found this on a chevelle forum and figured we could use a stickey disc brake conversion thread. So my question is I see where they mention converting drum spindles to disc spindles does anyone know what needs to be done to do that?
  2. 12lives

    12lives Engage! - Jean-Luc Picard

    You are basically changing the spindle. There is no "conversion".
  3. Brandon Cocola

    Brandon Cocola Well-Known Member

    As it said above you can machine the drum spindle to accept the disc brake but what needs to be machined?
  4. 12lives

    12lives Engage! - Jean-Luc Picard

    OK - I missed that bit - don't know. But for the price of used/new ones - I'd go that way unless the "hot rod DIY" spirit is strong!
  5. Brandon Cocola

    Brandon Cocola Well-Known Member

    There are 2 reasons why I am looking into this one is well I have drum brake spindles and the other is I heard cheap spindles can break. Other wise I will start looking for used one's to fit a little at a time budget.
  6. BubbaJ

    BubbaJ Active Member

    I went with the ATS setup from Savitske. Check out the pics in Member's Rides. I just got 17s for it which is the smallest that will fit on these spindles.
    AR wheels VN501 with BFG 275-40-17.. It is taking a while to do this because it aint cheap :eek:o_O
    Looking at the brake kit from kore3. Tobin knows this stuff pretty good. There are so many pieces to the puzzle and I just wanted bolt-on and work good..
  7. BubbaJ

    BubbaJ Active Member

    sorry.. correction... they are not the smallest wheel that will fit, just the smallest with any width- I had the old 14x6 on there for a while to keep it rolling
  8. UNDERDOG350

    UNDERDOG350 350 Buick purestock racer

    You need to mill about 5/16" off the top lug of the spindle. Where the brake shoe anchor/pivot bolt fits. The thickness of the caliper bracket.
    Not all spindles are the same.
    It was mentioned somewhere that Stage 1 disc brake spindles were heat treated differently.
  9. Brandon Cocola

    Brandon Cocola Well-Known Member

    knucklebusted likes this.
  10. knucklebusted

    knucklebusted Well-Known Member

    That looks like a perfect factory swap. All you need is a prop valve and master cylinder to match.

    Also, I have the tall upper ball joints with tubular control arms with additional positive caster. It handles like a new car and I stopped wearing the outer edge of my tires out.

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