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Drum Drilling

Discussion in 'Early CJ5 and CJ6 Tech' started by wheelie, Jul 23, 2022.

  1. Jul 23, 2022
    wheelie

    wheelie beeg dummy 2024 Sponsor 2023 Sponsor

    York, PA
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    Drilling my brake drums, as some of you know already. Thought I'd post some pics. Some people say it helps a lot with wet brakes/water crossings and others say it doesn't help at all. Guess I'll find out first hand. I gots to know. My brakes stink IMO so I thought I'd try something to make them better, in the wet anyway. It's just an experiment really. I'm going to swap to discs up front soon and I'll move these 11" drums to the rear regardless of whether this works or not. But I am hoping for better brakes for CO this year.

    I had some inspiration from those who went before and made this template for the holes. Made a different one for the 10 inchers (on the back of the JEEP) which will have fewer holes. This one seems like a lot of holes, one every 20 degrees. The template for the 10" seems like maybe not enough with a hole every 30 degrees.

    The 11" template:


    I've been thinking about this for many years. Since the Lynn Klingel days for those who remember him. I made part of this crude jig back then when I welded a hub to a piece of pipe. It's been moved and lost and found and sitting in the corners of several garages since then. Yesterday I made the rest of the jig. Very crude by most standards but it worked okay. I'd make it better if I had a lathe but I don't. If drilling the drums works for me, I may well improve this thing.


    Layout work. I goofed a little. The outer most marks actually would have drilled into the face of the drum. I'll drill the center row and inner most marks and maybe move that third row to the inside of the flange.





    Mounted up.



    Also made these little doodads yesterday. They screw into the captured nuts that should hold down a rear seat in the bed of the JEEP. I'll use these as tie down points in the bed.



    It was 87 in the garage at midnight last night. If I leave a door up, a little or a lot, to let the cool night air in, well, that cool air comes with 1000 Japanese beetles and 2000 other bugs that flock to the bright light. So I sweated it out for a while until I didn't want to anymore.

     
  2. Jul 23, 2022
    Oldpappy

    Oldpappy A.C. Fults - Curmudgeon at large 2022 Sponsor

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    Wish we had temperatures that cool. We have been hitting three digits for the last couple of weeks with enough evening storms to keep everything nice and muggy.

    Interesting idea, I have 11" drum brakes on my Jeeps and will be interested in your results.
     
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  3. Jul 23, 2022
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

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    There used to be a drilling template floating around, IIRC alternate holes were staggered a bit , maybe it works better to get the water out or maybe it helped with crack prevention?
     
  4. Jul 23, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Admire your energy and skill but is there a practical need for the holes to have any specific layout?
     
  5. Jul 23, 2022
    wheelie

    wheelie beeg dummy 2024 Sponsor 2023 Sponsor

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    I dunno. Its just how everyone has done it. can't imagine it would have much affect on balance but maybe. I prefer some symmetry vs random madness.

    Howard: Yes, I have staggered the holes. You can see my reference marks on the one picture of the template. Maybe the one with the drum on it.
     
  6. Jul 23, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    The later drums have fins cast in, and I'd think you could use that to control your spacing. Count the fins and pick an even divisor (and hope the count is not a prime!) No need to index, only needing a consistent placement across the width of the drum.
     
  7. Jul 23, 2022
    colojeepguy

    colojeepguy Colorado Springs

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    drilleddrum2 (Small).JPG
    I drilled my drums in groups of 3, staggered across the face of the drum.
    I wish I could remember where I found the instructions to do this....
    This isn't my picture but mine are like this.
     
    Last edited: Jul 23, 2022
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  8. Jul 24, 2022
    Keys5a

    Keys5a Sponsor

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    I looked at an old Series lla Land Rover axle on my pile this afternoon. It has holes drilled in the drums from the factory. There are only 4 or 5 holes, located near the inside corner of the friction surface.
    I thought this was interesting.
    -Donny
     
  9. Jul 24, 2022
    wheelie

    wheelie beeg dummy 2024 Sponsor 2023 Sponsor

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    My work will resemble Doug’s. I may be spaced out a bit farther as one set of holes is likely to end up between the cast flange and the inside edge of the drum closest to the backing plate.
     
  10. Jul 24, 2022
    colojeepguy

    colojeepguy Colorado Springs

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  11. Jul 24, 2022
    wheelie

    wheelie beeg dummy 2024 Sponsor 2023 Sponsor

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    Thanks Doug. That's the thread and info I used also. Mentioned earlier as "inspiration from those who went before."

    I got the fronts all drilled. Considering doing the rears too.

    Another problem I have is that the lines from the master cylinder are reversed. They go to what I believe is nothing more than a distribution block (vs a proportion valve) that was factory on the '71.
    The firewall mounted master cylinder is for an intermediate and all the lines coming out are the same size. I'm thinking about switching the lines but, after reading a bunch of stuff about others who also had lines reversed, no one with drum/drum brakes seemed to think it made a difference. Wondering what others here think. I'm just amazed how many people say their 11" drums work so well yet I feel mine mostly suck. Everything is properly bled and no air in the lines. Maybe it's the remaining 10" rears that are ruining it for me.
     
  12. Jul 24, 2022
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    The fronts and rears get the same pressure, since the MC has a single bore size. Front and rear have different diameter cylinders though. Almost all the braking is done by the front wheels, and its cylinder should be larger in diameter.

    I would expect the smaller chamber to go to the rears, since those cylinders are smaller. Really, the amount of fluid moved, once the cylinders are full, is small. A 1" brake cylinder moving 1/4" is about 1/10th of an ounce; maybe 1/2 ounce for all four pistons fully applied.

    Starting in '74-ish Jeep used a combination valve on the CJ with 11" drums. It had two sections, a proportioning valve for the rear wheels, and the brake failure light switch. The switch was triggered by a pressure difference front and rear, while the proportioning valve only acted in severe braking. The rear gets very light in severe braking, and the valve would meter pressure to the rear to keep it from locking up.

    My '75 came with manual brakes. They stop ok; takes some muscle, but not bad. Likely a revelation compared to the original 9" brakes.

    Kinda think your combo should work as well as factory 11" drums. I'd make sure the cylinder sizes are right.
     
    Last edited: Jul 24, 2022
  13. Jul 24, 2022
    wheelie

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    Thanks Tim. Good info. The wheel cylinders are correct and almost new.

    I'm going to leave it alone for now. I'll soon be going to discs up front and moving up to 11" at the back. These drilled drums and the organic shoes will find their way onto the proper backing plates at the same time. I'll likely use a late 70's jeep master cylinder for disc/drum. No power brakes.

    The new shoes are wearing in and I think things will be better after they have more miles on them.

    I'm still on the same 1/8" drill bit after drilling all these holes. The drums are pretty soft I guess and no oil was used in the drilling process. The jig worked reasonably well and allowed me to keep moving throughout the process.

    Put the drilled front drums on, adjusted them up a tad on the tight side for my liking. I'll take her for spin tomorrow after work.
     
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  14. Jul 24, 2022
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Cast iron, it's made to machine easily.
     
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  15. Jul 26, 2022
    Rick Whitson

    Rick Whitson Detroit Area 2024 Sponsor 2022 Sponsor

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    I don't drive my Jeep in water, but I did park on the boat launch for a Fishing Picture. I was surprised how long it took for them to come back to good after that. If I had a Mudder, I would give that some thought. Good Luck
     
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