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Drilled drums
https://www.ausmini.com/forums/viewtopic.php?f=2&t=12836		 Page 1 of 2
Author:  Brown Clubman [ Fri Nov 04, 2005 9:34 am ]
Post subject:  Drilled drums
Has anyone heard of this before?

I heard the other day that this "secret practice" is used in The States for Hot Rod drag cars to improve braking WITHOUT fitting disc brakes???

Would love to know more about this if anyone here has heard of it.
Author:  simon k [ Fri Nov 04, 2005 10:04 am ]
Post subject: 
a little bit of google came up with these, for "drilled brake drums"

http://www.tffn.net/drilldrum.html
http://www.chtopping.com/CustomRod4/

I've seen cooling ducts cut in drums on cars at the wreckers - they'd been cut into the edge of the shoe face, didn't look good.... get an old-ish set of drums and give drilling a go, the second link gives some interesting theory about why it works well...
Author:  fuzzy-hair-man [ Fri Nov 04, 2005 1:39 pm ]
Post subject: 
As mentioned the in the bottom article disk rotors are drilled to clean pad material away from the rotor I can't see any reason this shouldn't work on drums as well.

Heat build up is the killer for drums :(: so venting is sure to help. :D

The size of some of those holes though they don't look real big :? most of the holes are going to be covered by the brake shoes though so I don't know how much heat it could get rid of...
Author:  drmini in aust [ Fri Nov 04, 2005 1:40 pm ]
Post subject: 
Many years ago in the days of heavy cars with drum brakes, it was common to drill drums and backplates for cooling, fit air scoops on even.

But NEVER drill the outer part of the drum where the shoes run- only do it on the side of the drum. :wink:
Author:  Brown Clubman [ Fri Nov 04, 2005 1:54 pm ]
Post subject: 
skssgn wrote:
a little bit of google came up with these, for "drilled brake drums"

http://www.tffn.net/drilldrum.html
http://www.chtopping.com/CustomRod4/

I've seen cooling ducts cut in drums on cars at the wreckers - they'd been cut into the edge of the shoe face, didn't look good.... get an old-ish set of drums and give drilling a go, the second link gives some interesting theory about why it works well...


Thanks heaps skssgn. Appreciate it.
Author:  awdmoke [ Fri Nov 04, 2005 2:06 pm ]
Post subject: 
drmini in aust wrote:
But NEVER drill the outer part of the drum where the shoes run- only do it on the side of the drum. :wink:


I know it could lead to cracking, but those guys have done it with no ill effects.
Of course, it is worth bearing in mind that if you have a single circuit master cylinder & you had a catastrophic failure of any one drum, then you will lose all brakes :(

But how likely is that? Disk brakes are regularly drilled to improve performance, and it doesn't seem to increase the failure rate :?
Author:  Circus_Maximus [ Fri Nov 04, 2005 3:18 pm ]
Post subject: 
However disks have calipers pressing both sides at once resulting in no sideways deflection whereas with drums the force is all on the inside.... trying to get out :roll:
Author:  drmini in aust [ Fri Nov 04, 2005 3:22 pm ]
Post subject: 
And, they are cast iron; pretty strong in compression, but pissweak in tension,ie. with shoes pressing outwards.... :shock:

Also, drilling the periphery will greatly reduce swept area.
Author:  simon k [ Fri Nov 04, 2005 4:59 pm ]
Post subject: 
after reading what Kev's said, maybe the drilled drums are just a track day thing

probably a hundred hours track testing and regular crack testing before using them on the road... I'm sure any insurance company would have a field day if there was an accident too, even if not caused by the brakes
Author:  fuzzy-hair-man [ Fri Nov 04, 2005 6:03 pm ]
Post subject: 
drmini in aust wrote:
And, they are cast iron; pretty strong in compression, but pissweak in tension,ie. with shoes pressing outwards.... :shock:

Maybe that's it :D
drmini in aust wrote:
Also, drilling the periphery will greatly reduce swept area.


Disk come drilled and they would have less contact area with the pads/shoes than drums :?
Author:  Brown Clubman [ Fri Nov 04, 2005 6:10 pm ]
Post subject: 
drmini in aust wrote:
Also, drilling the periphery will greatly reduce swept area.


Please explain :? are you talking about a loss of surface area for the shoes to work on?

I've emailed the dude in CA to ask if he's ever done any such work on mini's and if he would see any issues in doing so.

Will post his feeback here if/when I hear back.
Author:  drmini in aust [ Fri Nov 04, 2005 6:15 pm ]
Post subject: 
Brown Clubman wrote:
drmini in aust wrote:
Also, drilling the periphery will greatly reduce swept area.


Please explain :? are you talking about a loss of surface area for the shoes to work on?

I've emailed the dude in CA to ask if he's ever done any such work on mini's and if he would see any issues in doing so.

Will post his feeback here if/when I hear back.

Yes I am. Drums rely on surface area to work, also on rigidity. The pressure of the shoes outwards tends to force them out of round.
This does not apply to squeezing of discs- a drilled disc is not a good analogy here..
Author:  simon k [ Fri Nov 04, 2005 7:58 pm ]
Post subject: 
drmini in aust wrote:
Brown Clubman wrote:
drmini in aust wrote:
Also, drilling the periphery will greatly reduce swept area.


Please explain :? are you talking about a loss of surface area for the shoes to work on?

I've emailed the dude in CA to ask if he's ever done any such work on mini's and if he would see any issues in doing so.

Will post his feeback here if/when I hear back.

Yes I am. Drums rely on surface area to work, also on rigidity. The pressure of the shoes outwards tends to force them out of round.
This does not apply to squeezing of discs- a drilled disc is not a good analogy here..


good point - the drums on the back of my cooper are out of round right now... new set on order
Author:  Angusdog [ Sat Nov 05, 2005 9:18 am ]
Post subject: 
Legally, I very much doubt it would be a good idea for use on the road, and probably not on the track. It would be much more common if it (a) actually worked and (b) was safe. If you're in any collision, and your brakes are modified in the manner of something you "heard about on the internet", the cops are going to bring charges.

Superfins are probably the best bet for improving drum brakes*, but importing one set is a bit of a pain. Someone needs to either manufacture them in Australasia or import a container load.

* Alongside careful adjustment and maintenance, and good friction material.
Author:  slide [ Sat Nov 05, 2005 11:59 am ]
Post subject: 
I run alloy MInifins with drilled (swiss cheesed) backplates on my S.

The back brakes don't really do all that much anyway - 70% of braking is done by the front discs.

The Mini is not all that heavy, so it's overkill to fit rear dics to it.
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