Sterling Disc brake Swap and related info

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Sterling Disc brake Swap and Related Info


Even though I was running one-ton axles (88 Ford 60, 90 Ford sterling) and their respective one-ton brakes, my braking has always been less than adequate in my opinion. Granted, the fault could lie in the 40” tires or the 7000+ pound weight of the rig, but I wasn’t satisfied. Long ago, I switched to a 94 F350 Booster, and 1 1/8 bore master cylinder, and ditched the 4WABS computer. I’ve been running the stock axle brakes with upgraded booster and MC for a few years, and never felt like the bronco would stop well in a panic stop. With a baby on the way, and desires of him and the wife coming on my wheeling trips, I wanted some better braking. I want to stop RTFN (right the F now) when I need to. With that, however, I also want decent modulation, reliability, and ease of maintenance. My solution was a disc brake swap, but, that lead to several other changes as well.

BACKGROUND INFO
First up was deciding what disc brake “kit” to use. I priced out TSM and a few other vendors, and while their kits are supposedly bolt on, I didn’t like the exorbitant cost. I had also read of some quality issues with the TSM kit in the early days of its production. Other vendors, such as Great Lakes Off Road wanted to sell “bolt on” kits that required making your own spacers, and either machining or hand grinding the back of the sterling hubs down, so that you could use a 70’s Chevy K20 front axle rotor.


factory hub


required ginding to slip chevy rotor on


another pic


I originally bought the GLO (Great Lakes Off road) brackets for the 65 dollar cost. The GLO bracket was nicely cut, but I had a few issues with using it.. The first issue I had, was that the bracket didn’t leave much metal around critical bolting areas.


GLO bracket on top, next to the one I cut. Note the minimal metal around the bolt holes


The other issue I had was that it required the use of a late 70s 3/4 ton Chevy 12.5 rotor that would press on from the back of the hub. I looked at using several different rotors for this application, and they all ended up with nearly the same result. The Chevy k20 rotors (Napa part number 4886242) are 12.5” diameter, with a 2.75” height (measured from the back of the rotor face to the front of the mounting side on the hat). They are designed to press onto the backside of a front axle hub. If you look at the center hole on the rotor, it has a chamfered edge, which is designed to press against the backside of the hub, which has an equal but opposite chamfer.


Dana 60 hub for reference. Look at the chamfered edge on the left side of the wheel mounting surface. Tis is what presses into the front of the rotor.


front of chevy rotor, the chamfered edge is clearly visible in this pic.


These opposing “miters” (for you construction people) are designed to locate the rotor hub-centrically. The wheel studs are then pressed through the rotor, and into the hub. People who do similar brake conversions on 14 bolts and 60’s will usually find a lug that has a longer and bigger diameter knurl, so that their stud (and its knurl) actually presses into the hub, in addition to the rotor. The problem with the sterling hub is that the factory studs are the largest 9/16 studs available, and in fact, are the ones that 14B and 60 guys use. The Dorman number for our lugs is 610-303, and is for an 85 to 97 ford. It’s a 9/16 –18 stud that is 3 and 9/32 long, with a .677 knurl and 15/16 shoulder.


ford sterling lug 610-303



other common studs. 610-301,610-194 and 610-189. Note the larger shoulder on the 2 chevy studs to the right of the ford


The only way to get the stud knurl to engage our hubs is to go to a 5/8 stud with bigger and longer knurl. These studs do exist, but that would require changing the front also, and I didn’t want to resize everything. IF you tried to use the stock studs, the Chevy rotor, and the sterling hub, you would have MINIMAL to NO knurl engagement into the hub.


pic of sterling lug through chevy rotor. Notice no knurl is sticking through


The Rotor material is also not strong enough to hold the stud IMO (as well as a machinist I spoke with), for repeated bolting/unbolting of the wheels using an impact gun, which is something I like to do. In addition, because the stud would barely engage the hub, the stud would likely, wobble out the hole in the rotor. Some people have run it this way and JB welded their studs in place. That might work, but isn’t the “right” way to do it in my humble opinion.

Another issue with the Chevy rotor and our studs are that if you look at the shoulder size of 15/16, the shoulder area where the stud is supposed to sit in the Chevy rotor is much larger, and in a machinist’s opinion that I spoke with regarding machining my hubs, the stud would wobble, and wear away at the rotor which is made of a very soft material in comparison to the hub.


note the space around the ford shoulder when in the chevy rotor


As stated, the GLO bracket was built for a 12.5 rotor diameter and recommends the Chevy rotor. I believe it went with the Chevy stuff based on price and commonality. One of the nice things about using a 12.5” rotor is it allows for 15” wheels. I tried a variety of rotors with varying hat depths to see if I could get away from having to use a spacer. The spacer is required to move the caliper bracket back to the proper location so the caliper aligns properly on the rotor. Here are some rotors and their specs.

Older Rotors
78 Ford Napa #85731 12.5” with 3.225 height
78 K30 Napa # 85843 is 12.875 by 3.080
80’s Dodge Napa # 85864 is 12 and 13/16 by 3.26
70’s K20 Napa # 86242 is 12.5 with a 2.75


Newer Rotors
02 Chevy P/U Napa # 86242 12.5 by 2.75
96 Ford E350 Napa # 86799 is 12.83 by 3.87
05 Chevy Van Napa # 86999 12.795 by 3.51
05 Chevy truck Napa # 86830 13.0 by 3.42



Obviously, there are lots of rotors out there, with different specs. Several people have done disc swaps, which required grinding down their hubs, and are successful so far. I’ve even come across one person that ground the front of the hub down so he could use the dodge rotor listed above.


sterling hub ground to fit 80’s dodge rotor from the front

http://www.supermotors.net/getfile/322746/fullsize/build_002.sized.jpg[/img
dodge rotor installed with GLO bracket,

[img]http://www.supermotors.net/getfile/406430/fullsize/attachment.jpg
no spacer needed with bracket on front of flange

As stated, most rotors are designed to press in to the back of the rotor, except for the newer, rotors, which are designed to use a drum style parking brake with disc brakes. These are found on late model trucks and vans. Since Ford went metric on their trucks, I was relegated to Ford Vans (which use a Dana 61 rear axle) and Chevy stuff. I couldn’t find much info on Dodge trucks, and know very little about them. Of the rotors I listed above, the new Chevy rotor slid over the outside of the hub, but had a small gap around the hub, which gave it some room to float around and put all the weight bearing onto the studs. I didn’t like that, and felt it would be hard on the studs. I tried the Van rotor, based on some info from Traveler (from various sites), and it fit like a glove. The Sterling hub even has a small flange the rotor sits on, which locates the rotor both hub centrically, as well as lug-centric, thus giving the best of both worlds.


back of van rotor. Note the chamfer on the inside as opposed to the outside of the chevy rotor


flange/chamfer on the front of the sterling hub

So now I knew which rotor I wanted to use, it was time to get to some brackets that would work. As I mentioned, the GLO brackets are designed to use a 12.5 rotor, such that when you tried using a 12.83 van rotor the bracket sat up off the mounting holes by about .5”, and there was no way to modify them for use. I looked at using a spacer that would shim the bracket up which I would weld the GLO bracket to, but, that make bolting the brackets on quite difficult and there wouldn’t be much room to weld the brackets together. The other issue with these bolt on caliper brackets is that I rotated the pinion up when I welded on the spring perches for my application, and the caliper bolts on the Chevy calipers would hit the springs. This would not allow me to either install or remove the calipers (obvious problem here) without removing the whole bracket. However, if you are using stock location spring perches, the bolt on ones would work fine for you.

I tried some 10 dollar caliper brackets from AA manufacturing, based on a suggestion from a buddy who used them on his 60 rear.


AA bracket on the right of mine


The AA brackets are made from 1/4 metal and are designed to weld on. They too, however, were too short for me. I looked at sectioning them by cutting them crosswise, and then adding some plate between them to make them taller, but this also wasn’t the “right” way to do it for my son.

So, in the end, I bought a Mi-Tech plasma cutter from Dustball for about the same as the TSM brake kit would be, traced the GLO brackets, adding some height for the taller rotor, and cut my own brackets. I thought about trying to make a bolt on bracket, and the ones I made would have worked in this application, but again, I would have either had caliper bolt clearance issues with the leaves, or the caliper would be on the bottom of the rotor, and exposed to rocks.


another shot of my bracket next to GLO brackets


INSTALL
After grinding, drilling and tapping the brackets, it was time to put everything together.

The first step is to determine exactly what the orientation (think of a clock face here as you look down the axle tube) that you will want the caliper to sit, so that the pins do not hit the springs when you try and mount/remove the caliper. If you use Chevy half-ton calipers like me, they mount via two slide pins that thread into the bracket.


pic of chevy caliper mounted with bolts in place


I took some 3/8 thick flat stock I had lying around and used some clamps to secure it to the spring pack. I had the flat stock stick out far enough that the caliper pins (bolts) would hit the flat stock as you rotate the caliper/bracket around the axle tube.


after pic of the flat stock clamped in place


Once I had the flat stock on, I reinstalled the hub to proper torque and mounted the rotor to it. I used 4 lugs per rotor so I was sure that it was trued to the hub. The caliper will slide on the pins (bolts) as the pads wear down, so lining up the caliper and caliper bracket is very important. The first thing is to mount the caliper to the caliper bracket that you are using. Then push the bracket about 1/8” away from the mounting surface of caliper.


note how the caliper is back from the bracket a little bit


This space allows a little bit of movement when you go to put new pads on. With out this space, it would be very hard to put new pads in when you do a brake job. Once you space the bracket out some, slide it over the rotor, and shoot some CLEAN compressed air into the banjo bolt hole to push the piston out so the caliper squares up on the rotor. (Warning, do not do this without the caliper being over the rotor or having a block of some sort in the caliper. You can push the piston out too far.) Once that is done, you will need an extra set of hands.

Rotate the bracket/caliper combo up until the pins are just below the flat stock as pictured above. Have your buddy, wife, etc hold the bracket in position AND have them blow more compressed air into the caliper so the caliper trues to the rotor. While your partner is holding and blowing, tack weld the bracket to the axle tube. Recheck all your alignments, making sure the caliper is spaced that 1/8 or so off the caliper bracket. If all your measurements are good, go ahead and weld that bracket on completely.

Now go do the other side also. Once that is done, pull everything apart again and paint it all up.



While you are waiting for the paint to dry, you can move on to preparing the brake pads. Since the caliper is for a 12.5 rotor, the pads sit about 1/8 inch above the outside edge of the rotor. As a result, you have to chamfer the edge of the brake pad. I just used my 4.5-inch grinder to take the edge down. If you don’t do this, you will have a rim on the pad that isn’t used, which will likely crack, and ruin the pad.




Once the paint is dry its reinstall and it is plumbing time.


PLUMBING
For the plumbing, I went to AFCO racing based on Billavistas recommendation from the pirate board. They have a good variety, prices and fast shipping. I ordered the following parts based on Bill’s recommendation.



1 each Brake line clips #40260 (4 to a package)
2 each AN-4 to 7/16 90degree elbow for caliper #40272
2 each AN-4 brake lines, 12” long #40262-12
2 each AN-4 to 3/16 inverted flare # 40276


With this stuff I was able to plumb the rear. OH, I also got from somewhere (probably AFCO, but I don’t recall) 2 each little brake line mounts that the clips and fittings get secured to. I bent all new rear brake lines from the drop line junction block out.



First I determined where I wanted to run the braided lines, and welded the mount on. Once that was done, I secured the braided lines to the mount with the clips and bent the new rear brake lines as shown above.



Once this was all done, it was time to move up to the master cylinder end of the plumbing. With the rear discs, it was questionable as to whether or not I would need a proportioning valve. Since all the plumbing was either new or drained anyways, now was the time to add one. I also had been wanting to add hydraulic line locks for those times when winching and the parking brake wasn’t enough. So I went to summit, wilwood and Jegs for a few more items (look to links section for direct links to the part numbers).

Wilwood 1/8 pipe to 3/16 adapter fittings
Wilwood adjustable prop valve from summit
Jegs stage control valves (line locks)
More 3/16 brake lines


The first thing I had to do, was find a place to mount the valves. I have is little to no space on the fenders due to my auxiliary fuse panel and shower, so after a lot of contemplation, I finally came up with making a bracket that would mount to the M/C bolts. I cut it from some 16 gauge metal (the plasma came in handy here too) and did a trial fit.



Once I was sure it fit, it was just a matter of painting, mounting and plumbing. This plumbing was a little tough do to the short lines, and it required that new drop lines be used to the front and rear brake lines (keep in mind I DO NOT have the stock 4WABS controller). I used a large socket to make some coils in the drop lines so the body could flex without kinking the brakelines.






Once the plumbing was done it was time to bleed the brakes. BUT, I got a hair up my butt, and decided that now is the time for Hydro boost brakes. Ill do a write up for that someday if there is interest, but it doesn’t apply to most people since most people don’t have a modified Saginaw steering pump or hydraulic assist steering. While I was at it, I re-plumbed the front 60 also, so that all my brake lines are the same fitting

There are some more pics and info on my superford page also
http://www.supermotors.net/clubs/superford/vehicles/registry/1278/34276-4




LINKS

AFCO http://afcoracingproducts.carshopinc.com/
GLO http://www.greatlakeoffroad.com/
VANCO http://www.vancopbs.com/category_s/66.htm
TSM http://www.tsmmfg.com/2670.htm
Wilwood http://wilwood.com/Products/008-Components/001-FA/index.asp
Summit prop valve http://store.summitracing.com/partdetail.asp?part=SUM-G3905
Jegs Control valves http://www.jegs.com/webapp/wcs/stor...atalogId=10002&storeId=10001&categoryId=21387

Here is just some random pics