Spindle Rebuild
This was very straight forward and started with media blasting the spindle and steering knuckle. I masked the spindle shaft with aluminum foil tape. After cleaning the parts with acetone, I masked everything and applied heavy duty, satin gloss black powder coat.
The original dust covers were gold cadmium plated. Since most of the coating was gone, I experimented with powder coat to see what I could come up with. I was unable to find a gold cadmium color powder, but I did find a flat anodized aluminum powder that I thought might get close.
Since the powder lets the metal show through, I changed the aluminum oxide for medium grit glass bead. This is supposed to give a satin finish to the metal, which I believe it did. After blasting, I went over them with a clean wire wheel, cleaned with acetone, coated, and baked the parts.
Although not bad, it's not the finish I'd hoped for and it seems more appropriate for a carburetor. If you insist on absolute authenticity, you should probably just buy new dust covers.
With everything cleaned and painted, it was time to assemble the spindle. I ordered a new spindle dust seal and Timken wheel bearings. I could not find a torque value for the large, short nut. I searched forum threads and learned others had trouble finding the info, but the consensus was that 80 ft-lbs was OK. I torqued all bolts to 80 ft-lbs.
Rotor Removal and Hub Preparation
Before starting on the bearings, I inspected the rotors and noticed the inner surface on both was thicker than the outer, leading me to believe they had been resurfaced at least once. I'm almost positive these were factory rotors because they were still riveted to the hub. Some brake shops operating on volume surface these past spec instead of taking the time to remove and replace a worn rotor. Original factory rotors have the minimum allowable thickness stamped on the "hat", and for mine it is 1.215".
I measured the rotors and my suspicions were confirmed. BOTH rotors were too thin. I checked each rotor at the positions corresponding to the lug studs and took my reading from the center of the rotor surface. The readings varied a few thousandths, but were mostly out of specifications. Minimum reading on the drivers side rotor was 1.212" and the passenger side was even worse at 1.203".
Because third generation Corvettes use a fixed brake caliper, and because I chose to keep the stock caliper lip seals (see brakes), the new rotors would need run-out correction.
Using lug nuts to protect the threads, I removed the lug studs with a press.
Next I removed the bearing races using a large hammer and drift. You must remove most of the grease to see the grooves inside the hub. These are where the drift is placed against the bearing race. There are two for each race.
Here's one of the races I removed. Notice the varying color between the upper and lower portion of the race and the hatch mark pattern on the race surface. It seemed obvious to me the bearings need replaced. All the races I removed were in similar condition.
Next is separating the rotor and hub. These are mated with steel rivets and because I had ten to drill, I purchased a 5/16" and 3/8" cobalt drill bit. The slides show the steps:
- Use a large hammer and center punch to place a starting divot in the center of each rivet.
- Use the 5/16" bit first and drill in about 1/8".
- Use the 3/8" bit to remove the heads (where the hole wasn't exactly centered on the rivet, I was able to remove the head with a large flat tip screw driver).
- I placed the rotor, hat up, on a pair of 2x4s and used a 2x4 and 4 lb dead blow hammer to separate the rotor and hub.
- Finally I used a center punch and large hammer to remove the rivets. I tried using a press, but it mushroomed the rivet, which had to be ground off.
The final picture in the series shows the hub with lug studs, races, and rivets removed. It is ready for processing and mild machine work.
Some folks think it's not necessary to replace the rivets. I agree, but wanted to lock the run-out correction in place and saw a post that used 5/8" long 3/8" - 24 socket head screws. This required tapping the rivet holes for 3/8" - 24 thread (which can be done with no drilling). Later, you will also see that I had to countersink the rotor rivet holes so the socket head screw sits flush with the hat surface.
I wanted to protect the hub from rusting further, so I used a clear powder coat after I sandblasted it. This is the same stuff I used to coat the calipers. I have no experience with clear powder coat and no idea how well it holds up. After working with it I'm not too hopeful because it seems softer than the colored powder coat.
The last step in hub preparation is reinserting the lug studs.
UPDATE: After nearly a year, I'm sorry to report that surface rust has appeared on the hub. I baked the hub at 450 degrees for an hour before I applied the powder, so I can only guess that the clear was either intended only as a top coat over existing powder coat, or requires a second coat to get complete coverage. If you read my brake caliper post, you will see I have the same problem there. They sure looked good for a while.
Bearing Installtion
The series of slides at right show the bearing installation process. I used the Harbor Freight bearing race set. The inner bearing race was installed with the 65 mm head and a large hammer. The smaller race was trickier because the kit didn't have one that size. The purple one was closest, but slightly too large and I was concerned it may deform the race. Instead, I inverted it and gently tapped the handle until the race was seated. I probably could've used the press once I got it started. The third picture shows the race grooves mentioned earlier. After the races were installed, I filled the cavity with Mobil 1 synthetic bearing grease. I placed grease on the races and hand-packed the bearings.
The inner bearing has a seal that keeps dust out of the hub, so that has to put on prior to assembly on the spindle. It just so happens that the 65 mm bearing race setter fits nicely over the seal, so I used it to press the seal into place.
The rest is simple. The hub goes on the completed spindle, and the retaining nut is torqued to 20 ft-lbs. This is not the proper torque for operation, but is the torque recommended for correcting the run-out because it eliminates the bearing end play that can result in variable and erroneous readings on the dial indicator.
Rotor Run-out Correction
I made sure the rotors I bought had rivet holes. Some do not. I countersunk the rivet holes using a 5/8" countersink bit. It just fit into the rivet holes.
Run-out correction can get complicated because there are two sources of run-out: the hub, and the rotor. Since both contain run-out, there is an optimal hub-to-rotor position where the run-out is minimized. To check hub run-out, set-up the dial indicator about 1/4" from the hub's outer edge and slowly rotate it while watching the dial gauge. It will swing between two numbers, and the larger minus the smaller gives the total run-out in thousandths. The larger number indicates the "high spot" on the hub, so mark the lug stud nearest to it with a dot. If it's in or near the middle of two lugs, mark them both. Also find the low spot and mark it in case you need to put a shim there.
After I was finished marking the hub, I put the rotor on and took a run-out measurement. I repeated this until I found the rotor position that gave the least run out. When I found it, I marked the rotor next to the marked lug stud. When checking your run-out place the dial indicator between 1/4" - 1/2" from the rotor edge. For 1971 and later Stingrays, maximum lateral run-out at rotor edge is 0.005" with a maximum change not to exceed 0.001" over 30 degrees. Since this included bearing end play, there's even less to work with.
After moving the rotors around, I was able to determine that one had almost no run-out because it's position didn't affect the overall run-out. The other rotor had about 0.0015" of run-out. My problem were the hubs. Both measured about 0.008" run-out, which almost doubles at the rotor edge. My readings were 0.013" and 0.015". Clearly out of tolerance.
I purchased two 0.006" hub correction plates, the largest you can get, from Brake Align. They were expensive at about $17 each, and were not sufficient. After installing them, I still had 0.007" and 0.009" run-out. I though of purchasing another set, but was not comfortable with stacking them. In hindsight, it would probably not be worse than what I did.
Since any correction I made at the hub was roughly doubled at the rotor edge, I was looking for something 0.0035" - 0.0045" thick for zero run-out. Zero run-out is a goal, not a necessity. Some guys use washer shims, others cut shims from stock. I decided to go for the latter option and used coke cans as shim material.
Seriously...I read about it on the forum
Once I got the shim the way I liked it, I put the correction plate over the top if it, tightened it down and took a reading. I was pleasantly surprised (and lucky) to see the dial gauge show 0.00075". Definitely in spec.
I tightened the socket head screws to 35 ft-lbs each and took a final measurement, which is shown at right.
The other rotor was more difficult because of the added rotor run-out. When I added the shim, it changed the value and location of the minimum run-out. It was just over 0.003", but I wanted less than 0.002" to account for bearing play. I added some aluminum tape as a thinner shim material and covered about 1/3 of the hub, centered on the low spot. I put the shim in place and the correction plate on top of that and tightened the socket screws. The reading was now 0.00175" so I called it good. After torquing down the socket screws a final measurement came out at 0.00125, so some compression took place. Overall, getting the rotors set up was tedious, but I was pleased with the overall results.
Hub Bearing Pre-load
Before setting the pre-load, I loosened the hub nut enough to slightly lift the hub / rotor assembly from the spindle. I didn't want the pre-load procedure to be influenced by the position of the bearing on the spindle at the 20 ft-lbs I had it for rotor set-up. After reading several forum posts, I decided to use the following process:
- Spin rotor in in direction it would turn when car travels forward and simultaneously tighten retaining nut to 15 ft-lbs.
- Back retaining nut off untill loose
- Tighten retaining nut 50 - 60 in-lbs
SUMMARY: I would give this a 6 out of 10 because I had to dial in the rotors. While it's not hard, you have to be meticulous in your approach and patient, because it get's a little frustrating and tedious. It's not necessary to incorporate the socket head screws into your rebuild.
This project grew beyond the original planned expense and effort. While I had planned on replacing the seals and bearings, I had not planned on replacing the rotors themselves. Both rotors measured out of tolerance and had to be replaced. With rotors, shims, and hardware, I was over budget by $120. I discuss my reasons for keeping the blank rotors in the brake rebuild section.
There is not a lot to be done with the original spindle in the way of improvements, and suspension geometry improvements are usually had from purchasing aftermarket parts such as drop spindles. For my purposes, the stock spindles are fine.
I chose to powder coat these parts because they likely won't come in contact with the road, and the powder coat is durable and easier to apply than paint. Overall, I was pleased with the results, except where noted below regarding the spindle dust shield and hub.
Modifications: None.
Upgrades: None.
Spindle & Rotor