Register now to get rid of these ads!

Disc brake conversion on my 1956 Oldsmobile

Discussion in 'The Hokey Ass Message Board' started by Martin_F, Mar 7, 2014.

  1. Disclaimer:
    This is not intended to show the one and only right way to do this.
    It's just showing the way I did the conversion after looking at all kinds of different threads on here.
    I felt like there is a lot of information, but it's not really in a nice and organized way, so I'd like to show my progress all the way through.

    To start out, here is a picture of the car in question.
    My 1956 Olds Holiday Sedan:

    As for the kits, of course there is scarebird, but you only get the brackets from them, and you basically have to hunt for all other parts. They do send you instructions, that show what parts "should" work, but I didn't feel like going through all that trouble.
    Fortunately I found a guy on ebay that sells the whole package. So that is what I bought.

    Here is what comes in the package (shown for one wheel only):
    Not pictured are the brackets, because I had them already mounted to the car when I though about taking the picture.
    And also the mounting bolts.
    Those are 2x 7/16-UNF by 1.75 for the top bolts,
    and 2x 7/16-UNF by 2.00 for the bottom bolts. And respective lock nuts.

    This is showing the bracket installed on the spindle:

    Nice gimmick is that the bottom bolts have the right length, so they double as steering stop:

    There are two spacers in the kit, that move the rotor outwards some.
    One is for Olds and the other for Pontiac. They are both in the above picture, but you just need the smaller one for the Olds.
    Here is a sketch of how it's installed:
    This might also help somebody that would like to make his own conversion kit.

    When installing, the instructions called for some red loctite on between spacer an spindle. Here that is installed:

    After cleaning and packing the bearings with my favorite bearing grease...
    ... it was time to put the rotors on:
    I did need another washer to space the castle nut out far enough to align the cotter pin hole. No big deal.

    Next step is to put the calipers on. At first I wasn't able to get them on, but then I realized that there are little floating bushings on there that need to align just right to make it work. Forgive me, disc brake newbe here ;)

    After that I put the wheels/tire on to make sure everything clears.
    Also if you use the right wheels (80's to 90's Chevy half ton truck or van), you'll be able to reuse the stock wheel covers. Which of course I wanted to do.

    Here are the wheels you want to use:
    There are also rally style wheels out there that should work, but they are 1/2 inch wider. Getting close to the 7.10 stock tire width.

    Judging by memory, the location of the wheel did not change.

    Next up, master cylinder.
    I used a corvette style dual reservoir master cylinder, because it has brake line fittings on both sides. You have to mount the master out front, so you need the fittings on the "wrong" side compared to a regular hot rod setup, where the master would be behind the pedals.
    The other problem is the location in relationship to the frame rails. You wouldn't be able to use lets say a Mustang master.

    After getting a rough location and cutting a hole in the frame, I made a bracket that bolts to the frame on one side, and to the transmission crossmember on the other side:
    Here is the cut frame with support boxed back in:
    You can see there was a hole already in the frame that I just elongated to the back to make the master cylinder fit.

    Made up this brake rod, but the length would vary depending on the exact location of the master:

    Once I had all that done it was pretty much time to get the engine compartment painted and get everything plumbed up.

    Master cylinder finally in place:
    There is a 10 psi residual valve and adjustable proportioning valve in the rear circuit, and a 2 psi residual valve up front.

    Running up the frame and T-ing off to the wheels:

    Front crossmember:

    So there you have it...
    Now I just need to bleed the brakes and make sure there are no leaks.
    Then once I get my engine back in there I can report of how it works ;)

    Here is some more info from the conversion kit:
    Brake line clips: BHC9 SET
    Brake line: 1080056 GB16897 1997 Diameter 3.2mm HC
    Inner bearing LM48548
    Outer bearing: LM11949 QJZ2K
    Outer race (not used): LM11910 QJZ2K
    Rotor: 5595
    Caliper Passenger: 4208 131014
    Caliper Driver: 4209 131014
    Pads: AM01FF MD52-728A 13135 TS 16949 130812
    Bolts Top: 2x 7/16-16 x 1.75
    Bolts Bottom: 2x 7/16-16 x 2.5
    Lock Nuts: 4x 7/16-16
    Dust cap diameter: 2.080
    Seal OD: 2.568
    Seal ID: 2.000
    Last edited: Nov 9, 2017
    engine138 and Speedy Canuck like this.
  2. Great write up! Thanks for taking the time to give details and pictures.

    Posted using the Full Custom H.A.M.B. App!
  3. nice write up! I look forward to doing the same to my Pontiac next week.
  4. Nice work Martin!

    Don't listen to Dave: Ford grease will insure that your wheel bearings will last forever...

    I run DOT5 in everything I've ever owned own that didn't have ABS....

  5. C-10 CST
    Joined: Jul 4, 2011
    Posts: 267

    C-10 CST
    from Indy

    Nice work Martin, It looks great. If you don't mind can you give us the name of the eBay seller and the Cost?
  6. Thanks guys!

    Dave, if there was a Buick-Olds-Pontiac bearing grease, that's what I'd use. ;)

    If you do a search on ebay for item number 230796768611, that's the one.

    One more thing to add, I've looked through Speedways catalog today, and it seems like the brake hose, and the clips to mount to the frame are in there.

    Item # 91031311 for the clips and # 6178568 for the hose.
  7. 1954 rocket 98
    Joined: Apr 18, 2011
    Posts: 220

    1954 rocket 98

    looking good martin
    is this going to be a manual brake setup or do you have a power booster to install yet. also are you using the original pedal setup or something different.
  8. Great tech write-up! Wish you had done this a year back when I converted my 56 Olds. Really like the master cylinder bracket idea. My car is a manual trans car and had no good ideas to swap to a better master. I installed the little stock one. It works fine - except the 2psi residual valve needed to be removed. The front discs would drag after a stop - dragged a lot! Maybe the stock master has a RVP already.

    Thanks for the thread!
  9. inline 292
    Joined: Aug 25, 2006
    Posts: 296

    inline 292

    Excellent Tech, thanks a lot. I have a tube axle under my '53 Stude with '56 Olds spindles. Did that to match the Olds rear axle wheel bolt pattern. Makes this very interesting to me.
  10. It's silicone brake fluid you want:

    But complete flushing of the old fluid is a must. In fact to be on the safe side, I would remove the rear wheel cylinders and wash them out with brake cleaner.

    This type of brake fluid will not absorbe as much water as DOT 3,4 so there is less chance of rust forming. And as Dave said, it will not attack the paint.

    As for the grease, it a good choice. There was a tech brief (Ford) that came out the the late 50's I think that addressed their improved wheel bearing grease. It is a low friction grease, which works well with the Ford wheel bearing re-design of that time. It appears that many Ford customers were complaining of aching legs and backs. After exhaustive research Ford engineers traced the problem to the high friction of the wheel bearings. Which made the cars difficult to push when they broke down. :D
  11. No power booster, just manual brakes.
    Original pedals, just had to add a new brake rod to compensate for the master cylinder re-location.

    No, I wish you would have done this write-up a year back ;)

    Thanks, sounds like an interesting project you got going on there.

    I just filled the system with DOT3 and I didn't have any leaks.
    Can't remember which one now, but one of the components said to use DOT3.
    So if the paint thing is the only issue, I think I'll be fine.
  12. Martin, write down the casting number off of the calipers. Go to a good parts store and they can tell you what they are from if you do not know at the moment. They look to be GM mid size, but good to know just in case one goes bad.....
    Excellent tech! and great documentation.
  13. Wow, Martin, you have been busy!
  14. Firecat7
    Joined: Dec 11, 2011
    Posts: 254


    What are the rotors...bolt pattern...application...etc..??? Calipers??? Appear to be metric gm's ( 83ish malibu)....little more info be helpful...... Thanx...nice pix :)
  15. My notes:
    Rotor 1995-99 WT1500 2WD Front
    Napa 86258
    Wagner BD125206
    Raybestos 56258

    Caliper LH RH 1969-78 Eldorado Front
    Napa 242-2010 242-2011
    Wagner CR80940 CR80941
    Raybestos RC4167 RC4168

    Inner Bearing ?? year ?? - not sure on this one I used the one below

    Inner Bearing 53-56 Olds 1979-84 Colt Front
    SKF CBR51

    Outer Bearing 1971-76 Riviera 88
    SKF CBR3

    Wheel seal 1977 Riviera
    BCA 8871

    Dust Cap
    Dorman 13977
  16. I was installing mine tonight and had a tough time getting the calipers to drop into the brackets, they kinda get wedged in there and don't float within the bracket. I think I am just going to take the grinder and take a hair off the edge of bracket or caliper so it will allow the caliper to move otherwise the outer pad wont get pulled against the rotor.

    Did you run into this issue at all? I saw you mentioned something about not getting it to align properly with the floating bushings. Also, did you use any type of lubricant or anti-sieze on the bushings?
  17. Just tap on them bushings a little bit. They are tight, but you can make them move.
    Don't grind on them, since the need to be the right thickness to float.
    Once you tighten the two bolts that hold the calipers, it will align the way it's supposed to.

    I didn't use any extra lubrication on the bushing, but used caliper grease on all the other moving parts. Make sure the brake surfaces are clean though!
  18. The bushings float no problem, its the caliper that seems slightly too wide for the caliper bracket opening.
  19. Gotcha, that's weird...
    Did you buy a kit as well, or trying to make your own parts work?
    Last edited: Apr 21, 2014
  20. None of the kits I found for a reasonable price offered 5x5 rotors so I ordered the brackets through Scarebird and pieced together the rest based on the parts suggested by Scarebird with my wholesale account at work.
  21. Did you measure the two pieces? How much interference do you have?
    I would be worried about grinding. If you could get somebody to machine the bracket, that would be the save route.
    I feel like you need to take the same amount off of both sides, to keep the caliper centered, and the bolt holes will align.

    Got any pics of what you're working with?
  22. I'll be home and back working on it in an hour or so and ill post up pics then.
  23. Looks like you got it to work?
  24. Well I got it all together and I dont know what I did wrong but the front brakes wont release. I cant even back the thing out of my garage. Ill get back at it tomorrow.
  25. What did you do as far as residual valves go?

    Dog Patch said he had to remove his front residual valve. Maybe that's the issue?
  26. I removed the valve, but I figured out what it is. I don't know why but it seems like after putting the front end and disc brake kit on it severely changed my camber and offset so now whats happening is the back of the wheel is locking up against the upper control arm. I just had to have someone else in the car so I could peak up in there when it was happening.

    I should have measured the difference before and after to see if its from the brake conversion.
  27. OK, I figured out where I went wrong, when I reinstalled the uprights/spindle I put them on the opposite sides. Thanks for your help!
  28. Studegator
    Joined: Dec 22, 2008
    Posts: 81


    I am curious as to how your brakes are now working. According to what I find on your parts #s -
    Rotor is 1.25" thick = GM PU
    Calipers are mid 80's GM Blazer and PU application
    MC is corvette type.
    The mc is not a "quick take up" mc (stepped bore) that matches the calipers which should be the low drag type.
    Do you have full pedal every time?
  29. The car is not on the road yet, so I can't tell you how well it works.
    The pedal seems to hold decent pressure, but I can't say for sure.
    Still waiting to put the engine back in...
    I'll post an update as soon as I can!

    Thanks for your interest and concern though.

Share This Page

Register now to get rid of these ads!


Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.