Anyone else heard of this and know if it is effective/ safe? http://www.tffn.net/drilldrum.html The guy drills holes into the drum at the end of his cooling fins. Also was wondering if there is anything to the saying that bigger drums/shoes = better braking?
I'm willing to bet that after a period of time you'll see cracks develop around the hole. Yes bigger = better.. performance wise.
I dont think the holes would do any good. Besides by drilling holes in the surface area arent you taking away needed surface? Bigger brakes = better stopping. Its easier to catch a baseball when your mitt is twice as big (without drilling hole in it)
But what about drilled rotors. Same thing? Interested to see where this one goes but I'm too lazy to do the research.
Gotta keep the pads cool, gotta keep the friction surfaces clean, gotta keep the whole unit strong. The structural integrity of the drum relies on that band that is the friction surface. Cracks from continual heating and cooling on that critical area are dangerous. The picture below shows how factory racecars (corvettes) modified drum brakes to stay cool and therefore avoid fade. Getting air into and out of the drums is difficult to do, hence the fan. I couldn't find a picture of the drum itself, but the drum picture represents how they drilled the holes to line up with the fan blades. Cooling air came in from large cut out sections of the backing plate (be careful how you do that too!) and was blown out past the drum. Notice the screens for debris. On that cooling note: Cooling air can't get in if the hot air can't get out so allow me to suggest that some of these traditional cars effectively only have drilled backing plates for looks. I'd argue that their cooling ability is poor. . . I don't know of any instances where drilling holes in any friction surface is the best way to help cooling since, besides the fact that cracks eventually show up, it decreases the amount of metal available to dissipate heat. Some have drilled holes simply to clean the pad off. They can be staggered so they clean the whole surface. Grooving is the other way to do this. Drilling holes does not help stopping ability since less surface area is available to create friction. They look cool though.
I would have to say I dont see a problem with the theory. I would think it would work exactly like cross drilled rotors. whether or not it would still be balanced or crack or whatever but i think it would help get some heat out of the drum
Holes are less for heat and more for clearing g***es and debris from the pad surface. Slots or grooves were found to do the same thing better on later race cars. I would call the benefits marginal for that setup and say probably not a good idea.
pop mechanics late 60's early 70's had a cover with smokey yunick and picture of drilled drums or disc brakes what works best, if you go to the pop mechs online you can find it, he actually drilled the face where it meets the axle flange, gets the dust out and heat,, good read if nothing else i would look it up but my mind wanders when i go there to find somethig
From what I understand the holes that are drilled in cross drilled rotors aren't there to cool them, but to vent any "off g***ing" from the pad, and the slotted rotors helped free brake dust. That being said, I read that somewhere, possibly on the internet, and that doesn't necessarily make it true. So these holes wouldn't necessarily serve any good purpose. I agree with the earlier statement that if heat is a factor, drill the backing plates and use brake scoops.
And not to be adding gasoline to the fire, but dont the front brakes do 60 to 70 % of the braking anyway? Case in point my 95 Cavalier that I drove from new to 270,000 miles. The rear brake shoes were the originals.
I think CHTOPPING.COM used to offer and have a few write ups on drilling of drum brakes. One thing to keep in mind is race parts are inspected after each race and often replaced just as soon. I think part of the drilling of the actual drum was to displace water that would effect drums from stopping. If you see some drum brake race cars they drill the face of the drum very close in spacing that honestly looks dangerous but then again so is racing a 60's car. There is a guy on Ebay that sells some sort of Corvair fan??? that he mods to fit as pictured above in the brake drum.
I drilled the drums on my pickup, 40 brakes on a 29 RPU. It was suggested by an old-timer who had a fix-it shop, he had done it on an old box van, believing it helped brake fade. They are hard to see when wheels installed, but there are rows of 3 diagonal placed holes (from in to out) about 2" apart, much like drilled rotors. They are 3/16", then chamfered or countersunk. There was a huge difference in brake behavior, especially on longer trips with lotsa hills, or lotsa stop and go traffic. The brakes tend to stop a little faster, and don't have that "just slow down instead of stopping" that happens during brake fade. And yes the brakes were properly adjusted before, I had driven the pickup almost 2 years before I did this so knew it well. Another cool part is when the drums are removed, there was no brake dust, not on the internals or in that little pile thats always in the drum. Its been almost 5 years and there are no cracks, the shoes still have alot of life in them, and there is no uneven wear in either the shoe or the drum surface. I do adjust them regularly though, not that they need it. There was such a huge difference in braking behavior I did it on my 40, (but 3 years later! also it has f100 brakes) And with 3 years on them they're in fine shape. I'll post pics soon. TP
im not sure of your purpose . i would not think you would need cooling help unless you drive in steep areas alot . then just use the motor for braking . hmmm maybe im not seeing you thoughts correctly ............ steve
Good brakes are better for hills and traffic. Engine braking and stopping aren't the same. The '40 style non-bendix single pivot style brakes have a much different "braking curve" than bendix style, especially since only the top half of each shoe really contact the drum. I was just trying to maximize the stopping power without changing brake style. There was also an extensive airscoop system on the backing plates as well. TP
I saw an explanatin of why drilling drums works. There is a gas created when the shoe contacts the drum during braking. The gas can in some cases cause the pad to lose friction therefore decreasing brake performance. Drilling is an old school trick for alleviating this gas that causes brake fade on drum cars. Saw it on TV they had nice 3D animations to go with it
wow, i got a huge amount of replies for this one, thanks a ton guys! yes, i should've clarified my original purpose for asking about it, I was just looking for a better way to stop without swapping out the entire front clip (it's on my list of things to do tho) From the amount of positive reactions this has gotten, i might consider taking a table mounted drill to them and see how it goes. I'll keep doing research 'till i decide on anything. Keep the responses coming, I'm learning a huge amount from you guys! Thanks again!
http://www.chtopping.com/CustomRod4/ good info ^^^ even with the drums drilled, you've still got way more contact area than you'll ever see on a disc, short of some of the crazy stuff like 14 inch rotors and 6 piston calipers. is say do it, and then come back and let us know what we're missing ** one addition, if you go for it make sure you've got a good scheme to get all the holes lined up and even and what not.
I'd be inclined to support that. Also, because drum brake shoes are a lot bigger than disc brake pads, they shroud a lot more of the drum friction area. The amount of cooling air one can get between the drum in the shoe must be rather limited. I'd expect that more cooling is to be had off the back of the shoes and the inner face of the drum web, by conduction. In that case one would want a flow of air over the backs of the shoes: so how about a ring of holes through the web, just inside the top of the shoes? The holes could be angled to act like a centrifugal fan. The wheel would obviously have to have space in that area to receive the air and not block it.
Many, many things have an effect on braking performance. The biggest one is the brake's abilty to disipate heat. Brakes work by turning kinetic energy into heat. Once the drum gets to a certain temperature, the coefficent of friction drops, and it can no longer turn the kinetic energy into heat. Most brake drums are shaped like a cylinder and are very bad at getting rid of heat, especially with the backing plate blocking airflow from the back side. Disk brakes (most of them) are designed like a squirel cage blower, and with their open design, are much better able to get rid of heat. Surface area actually has very little to do with the friction, its all about getting rid of the heat. The holes help to vent the outg***ing, help to let the dust out, and help circulate air to keep them cool. I like zibo's work, he did the expirement, proved that it worked, and now we can all benefit from that.
i think it would help but i would be alittle scared of it drum cracking between the holes.i have a set of chrysler 8 3/4 drums that were drilled in the face of them.they were on my opel kadett g***er and they worked great{only has back breaks}they stopped me at the track just fine with no brake fade at all{118 mph}i think this is a better way to do it because you get more cooling to the brakes.the only downfall is and holes you put in your drums will allow water to get in them but also let it out.i will try to post a picture.if any one is interested in them im selling them.they are new with only 20 p***es on them the backing plates are chrome.the only reason i took them off was they wouldnt stop me before the staging lights after a burnout.so i did some work for a guy and he bought me some willwood disk brakes.
I have this setup on my 1933 - so called 'Rocky Mountain brakes. This idea dates back to the model T era. I was wondering if I can use these drums with '40 backing plates and shoes - anyone done this?
Perhaps we should take note of the line "...when drums are vented properly, so as to eliminate balance and material integrity problems...". Given that we are talking about brakes I personally wouldn't just drill a few holes whereever I felt like it on the drums. CH Topping have a pattern that they follow. Vince also told me the process improves braking by up to 30%.
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