Project Chevelle: Disc Brakes Tech Article
When we first acquired our 1972 Chevelle project at Speedway we took a long walk around the car to figure out how big of a task we had undertaken with the goal to make it drive and ride with the performance and comfort of a modern muscle car. At first glance the list of upgrades needed was overwhelming. Prioritizing our plan of attack, while also being sure to keep our project on the road during the upgrades was necessary. Who wants to blow apart such a pristine car to let it sit day after day waiting to be recalled to life?
At the top of our list was an upgrade of the 4-wheel drum, single master cylinder system that was an unfortunate set of boxes checked on this Chevelle’s order sheet. I assume that an attractive sticker price was the main determining factor when this Chevy was ordered and delivered to Langel Chevrolet/Olds in Norfolk, Nebraska.
Speedway’s brake offerings for the Chevelle range from restoration parts for the original drums, factory style disc brake conversion, to exotic 6 piston 14” rotor racing Wilwood brakes. While discussing the goals of this car, we had some wild ideas thrown around about many of the components. We all quickly agreed on what brake kit best suited our needs. Factory style 11” discs and GM mid-sized calipers are a great match for these cars, and Speedway now offers a relatively low cost upgrade to the kit including drilled and slotted rotors for only $35 more.
Knowing this car would see some light autocross type of testing, but mainly highway and cruise miles, everyone was in agreement that this kit would be the most effective and economical. It also primarily uses factory components, so roadside service parts are also readily available.
Installing the Front Disc Kit, part number 91031958D:
Adding disc brakes to original GM drum brakes on 64-72 GM A body cars is not possible without switching to disc brake spindles, or extensive machining on the factory drum brakes. I had my drum brake spindles on my 1966 GTO machined in this fashion and it was a big delay and really didn’t save me much money in the long run.
Speedway offers factory Disc Brake Spindles for 64-74 gm, part number 91034900. Or for better geometry and a 2” drop go with the G Comp Disc Brake Spindles, part number 91035000. We had installed the G comp spindles previously while upgrading our front suspension with tubular control arms, which makes our disc brake upgrade a bolt together affair.
The installation of these components is seamless on our Chevelle. The rotor retains all of the stock dimensions and bearings so there are no clearance or special fitment tricks to describe. There are two sets of holes for the steering arm on these spindles, being that they are a 2” drop.
The lower set of holes aligns the steering arm in the same position as a factory spindle, which doesn’t change the clearance of your tie rod end to the frame, or change the bump steer. The upper set of holes is to hold the bottom of the caliper bracket in alignment with the now raised candlestick of the spindle that holds the rotor and bearings.
We wanted our caliper and steering arms to match the gloss chassis black everywhere else under the car, so we painted them before assembly. The brake kit also included new flex hoses for the front, which fit into the factory brake lines and tabs. The added performance and better look of the drilled and slotted rotors peeking through our rocket wheels gives us a little more aggressive look and hints that our A body is sporting a little more than the performance that was delivered to Langel Chevrolet in 1971.
The rotors were shot with some brake parts cleaner to remove the rust preventative oil from the factory and prepare them to be bedded in with the brakes. When it came time to bleed the calipers, we made use of the Mityvac Vacuum Brake Bleeder, part number 91083895. It makes quick and thorough work of pulling air out of the previously dry caliper and brake lines.
We followed up with a test drive and did our best to drag the brakes lightly for a city block or so and let them cool for four blocks. We repeated this with longer duration of dragging the brakes until we could sense the heat in the pads giving us better braking bite with light pedal applied. Once we knew we had plenty of heat in the pads and rotors we drove around normally letting them cool down properly and heat cycle. This helped mate the pads to the rotors and break them in.
Future plans call for a rear disc swap as well, but for now the Chevelle feels much more sure-footed when compared to the original front drums. Brakes are often overlooked when pouring resources into our beloved projects, but as the number of responsible drivers on the road continues to decrease, they are a required expense. This kit from Speedway is a top-seller for good reason as it supplies a potent brake package at a very reasonable cost by making use of factory components.
If you have any questions about our brake kits, or the install of them, don’t hesitate to give us a call to speak with a technician. Chances are the tech will have some brake or transmission fluid stains on their shirt while they’re speaking with you! What gets that stuff out anyways?
