The Autoblog Project Garage: Big-brake install, Part III
Our new parts showed up in the second installment of this write-up, and after leaving them out in the barn for several months, we finally found some time to improve the stopping ability of our 1996 Chevrolet Impala SS. With improved stopping ability only a few simple steps away, we'll be able to hit future autocrosses and open-track days with more confidence.
The first step in the project was to start modifying a new set of spindles. The brackets that adapt Corvette C5 calipers to the B-body spindle mount to two of the three existing backing plate mounting bosses, but the holes need to be modified to accept a 1/2-13 bolt. Drilling and tapping the holes in a drill press or mill isn't easy due to the spindle's irregular shape, so we decided to build a simple fixture that would bolt to the slider pin mounting holes and allow us to easily clamp this part in a vise.
With the part now easy to grasp, it was a simple matter to drill and tap the holes in a Bridgeport mill. An ordinary drill press would also work just fine, but we'd suggest against using a hand-held drill. A local machine shop can likely provide assistance for a reasonable fee (less than $100, we suspect) for those lacking the proper equipment.
The shape of the spindles and the necessary cut line defied reasonable attempts to perform material removal in the mill (at least with our minimal skills), and so we decided to unleash our reciprocating saw to cut off the existing abutments.
People that are smarter than your author would be wearing proper safety glasses (or at least a set of side shields).
Mark the line with a paint marker or oil crayon, select a fine-toothed blade (14 or 18 TPI works well), and proceed slowly. Cast iron actually cuts very easily if you don't try to rush things; just remember that this isn't a pine 2x4.
Metalworkers will probably point out that a reciprocating saw is a carpenter's tool and that a cold cutoff saw would be a better choice and we'd agree, but the motor in our Craftsman Twincut burned up during some demolition work and we haven't had time to purchase something better.
With the first cut made, bolt up the new mounting bracket and see how things look.
As can be seen here, the primary area of interference was around the large socket-head cap screws which secure the new abutment bracket.
To make a bit more room, a cutoff wheel mounted on a right-angle grinder is utilized. We'd recommend keeping the guard in place, but these pictures were snapped before our latest visit to the ER and so we were still living dangerously.
After we ensured sufficient clearance, we then used the grinder and a hand file to smooth out the modified area. It's important not to leave any gouges or sharp edges, as these could form stress risers and lead to future cracks.
For clarification, an unmodified spindle is shown on the left, with the modified parts (and scraps) on the right. The instructions could have been a bit more detailed when describing the material to be removed; this was the only area of the instructions that we found to be lacking.
Once we were done creating metal chips, the parts were coated in some spray-on bedliner and left to dry while we disassembled the old setup.
The slider pins are removed using a 3/8" hex key, and the stock rubber hose was disconnected from the hard steel line near the frame.
The wheel speed sensor - used by the ABS system - is carefully removed from the spindle and set aside. Due to a decade of mild corrosion, a bit of gentle tapping with a plastic mallet was required to remove this sensor; needless to say, some caution is required when applying percussive force to electronics.
The cotter pin is removed from the lower ball joint, and we break loose the nut. Do not remove the nut at this time!
The rotor is removed, along with the backing plate.
Remove the cotter pin and nut from the tie rod, and then break loose the joint using a "pickle fork". Place a floor jack under the lower control arm, and use the fork to perform the same task on the lower control arm. Remove the nut from the ball joint, and carefully lower the floor jack. The shock and sway bar will keep the lower control arm from overextending.
The same task is then performed on the upper ball joint, and then the spindle can be removed.
This is obviously a good time to replace worn ball joints, and so we decided to take the opportunity to press in some fresh lowers.
The modified spindle can then be installed. Torque the ball joint and tie-rod end nuts to the proper spec, and use new cotter pins to secure the nuts in place.
Gently remove the toothed ABS reluctor rings from the old rotors. We used a three-jaw puller because it's least likely to damage the relatively fragile reluctors.
Install the reluctors on the new hubs, along with a set of packed bearings and the grease seal.
The ring seemed to fit just a bit looser than we'd prefer, so we applied a thin smear of red threadlocker before gently tapping it in place with a plastic mallet.
The backing plate isn't strictly necessary for a car that sees little foul-weather use, but we decided to keep it in place to duct cooling air to the disk. In order to mount it, two of the holes need to be opened up to 1/2". For this sort of work, a Unibit rocks - it's expensive (about $50), but is worth every penny.
The backing plate and adapter bracket are then secured to the spindle, with red threadlocker applied to the adapter bracket bolts. Tighten the fasteners to spec, and double-check your work as if your life depends on it.
The hub is then installed, with the bearings adjusted properly (Kore3's instructions provide a rather detailed explanation of the proper technique), and the fancy machined dust cap is tapped in place.
Oil and other contamination are removed from the rotor using brake cleaner, and then it is slid over the wheel studs and retained with a couple of lug nuts.
We installed the slider pins and dust boots into the abutment bracket (making sure to lubricate them with high-temp caliper grease), and mounted the abutment bracket to the adapter bracket using the supplied bolts and red threadlocker. The new pads were cleaned and set into place, along with a pair of supplied anti-rattle clips.
Additional pad hardware was installed into our bright-red C5 Z06 calipers...
...which were then slid over the pads and secured to the abutment brackets. The supplied bolts for the slider pins already have threadlocker installed, so they simply need to be torqued to spec (KORE3's instructions provide torque specs for all fasteners).
Topping off the install was the included set of braided brake lines, as the Vette calipers use a different hose end.
That's it! Repeat the job on the other side (it'll go about twice as fast), bleed the brakes, and install the wheels. Verify that no interference exists (be particularly careful of stick-on wheel weights, as they might contact the calipers), and drop the car back on the ground.
To bed the new pads, perform several moderate stops from about 50 MPH, and follow these up with two or three stops from about 70 MPH (obviously, observe all traffic laws and use some common sense when doing this). These speeds are considerably higher than what would typically be used to bed the pads, as the larger brakes are more difficult to bring up to temperature. Those with lighter cars may find that more speed or additional stops are required for proper bedding; if in doubt, contact your pad manufacturer for advice.
After performing the stops, cool down the brakes with 10-15 minutes of gentle driving, and try not to bring the car to a complete stop during this time (lightly-traveled backcountry roads are your friend).
You can now enjoy dramatically improved stopping performance, and we'll admit that we definitely like the looks of the new system as an added bonus. Next up is a freshening of the rear brakes, and we also plan on installing an adjustable proportioning valve so that we can fine-tune the front-rear brake balance.
The total project cost was about $1200 with the new spindles and ball joints (neither of which were strictly necessary), and we spent about six hours overall (as usually, photography and the usual workshop banter among friends are responsible for consuming at least half of that time). KORE3's kit provided excellent quality, the instructions were almost perfect (lacking only a bit of detail on the spindle modifications), and the value was exceptional. Without a doubt, this is one of the best modifications we've performed.
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