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Drilling Brake Drums

Discussion in 'The Hokey Ass Message Board' started by blackjack, Feb 25, 2007.

  1. I've just read a classic motorcycle tech page that suggests that the best way to cool drum brakes is to have a leading scoop on the backing plate and then vent the air out of holes drilled into the drum itself, rather than the trailing edge of the backing plate. The idea is that the airflow is then across the surface of the brake shoes. Here it is;

    http://victorylibrary.com/brit/2LS-c.htm

    I know that CH Topping do this in the USA but as I'm in the UK I wonder if any one here has done it and can pass on the technique?

    [​IMG]

    [​IMG]
     
  2. john56h
    Joined: Jan 28, 2007
    Posts: 1,760

    john56h
    Member

    Be careful driling drums and rotors because often cracks will develop because of the drilling.
     
  3. 4woody has it done on his Plymouth wagon. search for Mopar/Plymouth flathead six threads, it's mentioned there. Seems like there was a thread a while back about drilled/drilling drums too.
     
  4. Fraz
    Joined: Mar 3, 2001
    Posts: 1,818

    Fraz
    Member
    from Dixon, MO

    I risk being trampled by a herd of rabid platypi every day I walk outside, it still don't stop me from doing it.





    I'm going from what I remember from the article that Custom Rodder did on CH Topping. The story they gave is that there's a gas buildup that occurs when you put shoe to drum. Drilling lets that gas escape through the holes, helps with fade and stopping distance. Overall less brake usage - less heat buildup. Also, from what I remember, you don't want to get crazy with the holes, and stay away from the edges. Obviously if done improperly you could have a possible cracking problem. The pic on the bottom shows the holes well, a couple in the middle of the shoe contact area, 30-35cm apart and 75-80cm from the next set, and call it good.
     

  5. john56h
    Joined: Jan 28, 2007
    Posts: 1,760

    john56h
    Member


    Yes, that's my understanding too. Helps keeping glaze from building up as well. I've read that even just milling some grooves will have almost the same benefits with much less chances of cracking. The grooves I've seen are on an angle across the macined surface and are not very deep.

    I just mention the cracking because I wouldn't want to have some hard-to-find brake parts and then ruin them by too aggressively venting them and causing them to crack.
     
  6. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,208

    HemiRambler
    Member

    You asked for advice and you got a VERY good reply from John56h about being careful. You seem to want to ignore his comment. Were it me I'd be asking things like, "how can I be more careful....what do I do to be more careful." Maybe we could then explore the things one could do to reduce the chance of stress risers -things like removing the sharp corners left from drilling or......
    but what the heck - you have your artical what more do you need????



     
  7. Now what about the old myth of water getting inside the drum and the brakes not working wet ?
     
  8. hsheartaches
    Joined: Jul 3, 2005
    Posts: 460

    hsheartaches
    Member

    Is the Jockey Journal down?? Hmm....
    I would never suggest drilling brake drums. Not that it can't be done, not that it shouldn't be done....I just like stopping. They work fine like they are. Plannin' on going 150+mph and stopping on a dime?
     
  9. tattooedup37
    Joined: Nov 17, 2006
    Posts: 555

    tattooedup37
    Member

    I cant find that thread about drilling drums? Are there any better pictures of this process somewhere that I am not lookin'?
     
  10. dehudso
    Joined: Sep 25, 2003
    Posts: 545

    dehudso
    Member

    I would think that a couple slots milled across the surface would be enough to clean and de-gas the shoes. But on the other hand, I have heard that newer compounds do not de-gas. Can anyone shed some light on this?
     
  11. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    Not a myth.
    Water will act almost as a lubricant between shoes & drums. It is a barrier between the shoe & drum - of course, depends how wet they get too.

    However, drilling holes in the contact area of the drum will allow water to escape & nearly eliminate this problem.



    As for this subject - drilling drums - Here's how the search function works:

    http://www.jalopyjournal.com/forum/showthread.php?t=59099&highlight=drilling+drums
    http://www.jalopyjournal.com/forum/showthread.php?t=6470&highlight=drilling+drums
    http://www.jalopyjournal.com/forum/showthread.php?t=1820&highlight=drilling+drums
     
  12. TimDavis
    Joined: Sep 4, 2005
    Posts: 718

    TimDavis
    Member

    Fraz was not the original poster - read the entire thread before you post -

     
  13. Now, I wanna drill my drums & scoop my plates. Thanks, I'm never gonna get this thing ready for the RoundUp, ha.
     
  14. Oh, and we are always careful.
     
  15. Fraz
    Joined: Mar 3, 2001
    Posts: 1,818

    Fraz
    Member
    from Dixon, MO

    HemiRambler, I said I READ an article and was going off what I remembered. I never claimed to write the f'n thing, so back off. It's in an older Custom Rodder, like July 2001. They spoke with CH Topping hisself, and debunked several of the common anti-drum drilling statements. The impression I got when I read john56h's 1st post was the stereotypical "they'll crack" response people make as a deterrent to drilling a brake drum, and I commented as such. His reply to mine further expands on his concerns and the jibe you have issues with was by and by ignored.

    You will also note in my post that I said to drill conservatively. I never said go crazy, I said follow CH Topping's example of a few holes spaced evenly and away from edges and thin spots.



    John56h - I agree with you on the slots probably working as holes would. I also would like to see a slotted drum done. I am not sure how the slots would mess with things if the drum needed turning. I know that the holes don't, I have seen pictures of CH Topping turning a drilled drum. And I'd be concerned with the average joe being able to do it or not. I think that's part of the attraction of drilling drums. If a person thinks it through and is careful in the spacing and sizing of the holes, they can do it with a drill press and jig. I'm guessing you'd more than likely have to slot the drums on a lathe or milling machine.
     
  16. McGrath
    Joined: Apr 15, 2002
    Posts: 1,414

    McGrath
    Member


    I did mine a couple years ago, spaced about like the ones in the picture. It did improve the performance of the brakes noticeably, but don't expect miracles. Its still no replacement for Disc Brakes.
     
  17. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,208

    HemiRambler
    Member

    Drilling brake drums WILL increase the likelyhood of them cracking - if for no other reason than the fact that they are now weakened.

    Franz, Sorry I misunderstood your post - my bad. As far as "backing off" - get a grip.

    Modifying brake drums is serious business. Slotting them is a BAD IDEA no matter how you do the math or how carefully you think you've thought it through. The idea when drilling drums is to take away the LEAST amount of material that will do the job. The real "job" is to reduce fade or in this case look cool.

    You know guys this is just like the red plastic fuel lines. Those lines look great but they suck. Accepting that and adressing it (diligence and maintenence) is how you safely "get away" with it.

    Go look at some drilled race rotors - eventually they're gonna stress crack - those cracks will be radiating from the holes. Deburing holes is one way to reduce the likelyhood or at least buy you some more time. I'd rather squeeze a rotor than try and push apart a brake drum I just drilled full of holes or worse yet just slotted.
     
  18. hsheartaches
    Joined: Jul 3, 2005
    Posts: 460

    hsheartaches
    Member

    I never got the newsletter on brake drums not working unless they were drilled or slotted.....Fuckin' mailman!
     
  19. I'm thinking that I'll just put scoops on the leading edge of the backing plates and drill the trailling edge for now to get most of the benefits.

    Perhaps I'll source a second set and have them done by C H Topping next time I'm out in SoCal. If a company is offering this service in the litigious USA, even if it's just for "racing", it can't be all that risky??
     
  20. CoalTownKid
    Joined: Mar 12, 2005
    Posts: 2,024

    CoalTownKid
    Member

    two things,....
    #1. Dont do it,...weakens the drums,....ask UnclIan and others...

    #2. Use the Search and you'll see the topic has been discussed extensivly before,...lots of good info on those threads!!

    It would be wiser to just drill out your backing plates to help cool things off and relieve gasses and dust. That's what I'm doing!
     
  21. Scarebird
    Joined: Sep 26, 2006
    Posts: 960

    Scarebird
    Alliance Vendor
    from ABQ, USA

    another question is how much water will get into that scoop...
     
  22. Shifty Shifterton
    Joined: Oct 1, 2006
    Posts: 4,964

    Shifty Shifterton
    Member

    I used to hear all the same cracking concerns about cross drilled rotors and they're become a common street item on late models.

    A friend/coworker who was a sports car fanatatic used to drill his own rotors. He said the secret to longevity was to drill the hole, then come in with a ball mill chucked in the drill press and countersink the hole. I would imagine the same logic applies to drums.

    Then again there's probably a good reason why you don't see drilled drums more often.

    Good Luck!
     
  23. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,406

    Flat Ernie
    Tech Editor

    That's what I did up in post #11 :rolleyes:
     
  24. john56h
    Joined: Jan 28, 2007
    Posts: 1,760

    john56h
    Member

    Does anyone run the racing style backing plate with Buick drums?

    I think they were made by Frankland, and probably some others. I've seen them in steel and in aluminum.

    They basically eliminate all of the backing plate, except what is nescessary to mount the wheel cylinder and shoes. All the brake mechanism is visible from the backside of the drum.
     
  25. CoalTownKid
    Joined: Mar 12, 2005
    Posts: 2,024

    CoalTownKid
    Member

    racing is different from regular riding that we do on roads. Debris thatr can cause harm that is easily kicked up on the road won't enter small holes like 5/16" or so,.....compared to no backnig plate which equals NO protection to your brake system!
     
  26. CoalTownKid
    Joined: Mar 12, 2005
    Posts: 2,024

    CoalTownKid
    Member

    Racing is different from regular riding that we do on roads. Debris that can cause harm that is easily kicked up on the road won't enter small holes like 5/16" or so,.....compared to no backing plate which equals NO protection to your brake system!
     
  27. 39cent
    Joined: Apr 4, 2006
    Posts: 1,569

    39cent
    Member
    from socal

    I used to notice that the old riveted brake shoes worked better than the bonded linings, so thats what i bought. It is actually the same principal as drilled shoes. The gassing is relieved thru the rivet holes.
     
  28. Lotek_Racing
    Joined: Sep 6, 2006
    Posts: 689

    Lotek_Racing
    Member

    I have a couple Trans-Ams.. I know, O/T cars BUT..

    Herb Adams advocated drilling the rear brake drums on these cars to help increase stopping power.

    One car is a 1980 WS6 SE Turbo T/A with 4-wheel disc

    The other is a 1980 WS4 T/A with drilled drums.

    I have run both cars at autocross and I have noticed that the drilled drums resist fade better than undrilled drums and are nearly as good as rear discs until you really start heating them up.

    The Herb Adams mod consists of drilling five 1" holes in the face of the drum on the flat areas between the studs and outboard of the stud circle. The backing plate is also drilled.

    This uses the motion of the drum to pump air through the brakes and help cool them.

    The modification instructions never mention drilling the braking surface of the drum. I've heard of it but never done it myself.

    Shawn
     
  29. Scarebird
    Joined: Sep 26, 2006
    Posts: 960

    Scarebird
    Alliance Vendor
    from ABQ, USA

    If you do the Herb Adams trick, make sure that your holes are WELL chamfered...
     
  30. CoalTownKid
    Joined: Mar 12, 2005
    Posts: 2,024

    CoalTownKid
    Member

    Do a search on this topic,....and read about those who have already done this before and not just speculated about it!!!!!! i was going to do it myself on my Buick and my 27 T coupe,....I'd NEVER do it after reading that people's drums fell apart after the drum could not take the heat and cracked!!

    DO A SEARCH,....this will end all the wondering and give you guys some good info!!!!
     

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