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You are here: Home Tech Articles & Tutorials Steering / Suspension / Brakes Remanufacturing Disc Brake Spindles
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Remanufacturing Disc Brake Spindles

by Roman Traber


     On January 2004, I purchased a 1967 Ford F100 SWB Ranger truck. It has a 352 FE with a MX transmission behind. At the moment the truck is undergoing a frame off restoration. One point of this restoration is the change from the present front drum brakes to disc brakes. For this I bought a complete disc brake conversion kit from Master Power Brakes.

Fig. 01

     The included spindles were 1975-79 types. I thought that for $1045.00 everything should be complete and in best quality. Far from it! There were no dust shields as pictured in their catalog. The second and even worse fault was the condition of the LH spindle. The lower bore for the king pin bushing was extremely corroded. Because of this corrosion the diameter was increased by about 1mm (0.04"). Moreover the thrust face for the bearing was also worn out 1mm deep. Due to this situation, a standard rebuilding with the replacement of the king pin bushings would’ve been impossible.

     Of course I made a complaint to MP Brakes regarding this problem. After many emails with a lot of explanation and pictures, they agreed to send another LH spindle for free, but I had to pay the shipping costs. The new LH-spindle had an accurate bore but it was a 1973-74 type instead of a 1975-79 type. Now I had a good 1973-74 LH-spindle and a good 1975-79 RH spindle. I got mad!! 1973-74 spindles have other king pin dimensions as well as other bump stop features than the 1975-79 spindles. I don’t think it’s a good idea to use two different spindle types for one truck.

     After a lot of study, I decided to turn new bigger bores into the spindles on my lathe and to fabricate new bronze bushings for the kingpins to match. Now it's time for some pictures:

Figs. 1 and 2 show the defective LH spindle. On the first view it looks very clean..... but it isn't. The lower bushing bore as well as the face for the thrust bearing are corroded and worn out very badly.

Fig. 02

Figs. 3 and 4 show the device which I had to fabricate to clamp the spindle on the lathe. To find the correct center, I used a rod thru the existing bores. After this I welded a strong support with two ears on a thick steel plate. The steel plate was fastened with four screws on the lathe chuck. The spindle was fastened to the support ears with two screws. I used the threads for the dust shields.

Fig. 03

Fig. 04

Fig. 5 shows how the cutting tool goes into the upper bushing bore. It was very important to do the upper as well the lower bore in one chucking because of a perfect lining of the center axis. It was also important to cut from the middle part to the outside in a manner that the threaded ends of the bores were left untouched. These threads will be used for the standard threaded end caps with grease nipples. The diameter of the bores are approximately 27.5mm (1.083").

Fig. 05

Fig. 6 shows the cutting of the face for the thrust bearing. The removed material will be replaced with a made-to-measure washer of about 1.7mm (0.07") thickness. I needed to fabricate the pictured cutting tool by myself. The blade of this tool has to be inserted after the rod is already pushed thru the bore.

Fig. 06

Figs. 7 and 8 show the remanufactured spindles. After the LH spindle was completed successfully I decided to do the RH spindle in the same way. Both spindles are now ready to receive new custom-made bushings.

Fig. 07

Fig. 08
The next step will be to obtain a suitable piece of bronze and to fabricate the bushings as well as a device to line them up in the spindles.

Shown here is an almost-finished upper bushing just before cutting. I found a supplier for non-ferrous metal who had a suitable high-performance bronze tube in stock. I only needed to cut a small amount at the inner as well as at the outer diameter. I turned the inner diameter about 0.025mm (0.001 inch) bigger than the king pin diameter. The goal was that no additional reaming will be necessary after pressing in. For a light press fit I chose the bushings outer diameters about 0.015mm (0.0006 inch) bigger than the bores in the spindles.

Fig. 09

Here are the finished custom-made bushings. The upper bushings have a stepped face to hold the king pin seal. At left is the rest of the raw material tube.

Fig. 10

Figs. 11 and 12 again show the bushings as well as the device to press in the bushings in the spindles. The device should guarantee that the bushings are absolutely lined up after pressing in. For this I fabricated a guiding sleeve with an o-ring. The sleeve is only needed for a guided installation of the first bushing. The outer diameter of the guiding sleeve is a little smaller than the bushings. It can be installed by hand and is held in the bore by the o-ring. After the installation of the first bushing, the sleeve can be removed. The already-mounted first bushing guides the press rod for the installation of the second bushing.

Fig. 11

Fig. 12

This is the ram press which was used for the installation of the bushings. This equipment is located at the company where I work. This is the only picture because I needed both hands for operating the press as well as holding the spindle at the same time. For additional safety I brushed the bushings with LOCTITE_641 adhesive before pressing in.

Fig. 13

Here is the LH spindle with pressed in upper and lower bushings. The RH spindle was made in the same way.

Fig. 14
Reaming the grease grooves as well as adding the washers for the thrust bearing will be the last part of this story.

Figs. 15 and 16 show the self-made tool to ream the grease grooves. I thought a lot about how to get these grooves in the bushings. According the original bushings, the grooves should have a helical path along the inner shell of the bushing. I guess that the helical path of the groove results a better distribution of the kingpin's pressure force. I found that the following method gave really nice results. I took the shaft from the pressing device (see Fig. 11) and had it modified so that I was able to insert a tiny cutting edge. It was a hard job to grind this little thing by hand. The square-profile of the blade measures 6x6mm (1/4"x1/4"), the length about 20mm (3/4"). As many other guys in the later forties, I found out that the glasses should be changed to better ones. The blade is mounted so that its' cutting edge is 0.3mm (0.012 inch) above the circumference of the shaft. This measurement will give the depth of the grease groove in the bushing.

Fig. 15

Fig. 16

Fig. 17 shows the tool in action. I used the nylon hammer with light strikes on the upper end of the shaft. Due to the inclined fixation of the blade as well as light turning moment by hand at the shaft, the grease groove gets its helical shape in the bushing. Each bushing receives three grooves evenly spaced.

Fig. 17

Here's the finished upper bushing. The picture also shows the stepped diameter for the retaining of the king pin seal.

Fig. 18

Picture #19, #20 show the addition of the made to measure thrust washers. As described earlier, I had to rework the spindle faces for the thrust bearing. The removed material needs to be replaced in such a way that the distance between the bushing lugs is correct again. I fabricated two washers with a thickness of 1.7mm (0.07 inch) and pasted them with LOCTITE 638 to the machined thrust face of the bushing lug.

Fig. 19

Fig. 20

Picture #21 shows the spindle in the lathe again. As a final work I reconditioned the thrust face for the inner rotor bearing as well as the surface for the rotor seal.

Fig. 21
That's it! The spindles are now ready to use and should be within the original specifications.

Special thanks to forum member ‘jor’, who has helped to make this text readable.


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