I have '56 chev pickup diff and front brakes in my '40 pickup. This set up is better than the original Huck brakes , but it has always been twitchy when cold and also a little invigorating in the wet. It has been a while and many miles and is now due new shoes. I have been contemplating drilling the spare set of drums I have . I really don't know if doing this will help , but it was a thing to do once upon a time. Does anyone know why I should not do this?? or any other thoughts , thanks.
I used to do this on a 50 Cranbrook I had among others to avoid converting to disc. It did help with keeping the brakes more reliable and grippy to an extent. I used an indexer on a mill with carbide end mills 1/4 inch diameter. I would find center to the rotating axis of the drum and then dial 1/4 of the total diameter of the drum rearwards. By rearwards I mean if you had the drum back on the car, the endmill was closer to the rear of the car. So for an 8 inch drum that would be 2" behind axle centerline or x positive 2" with the drivers side drum facing you. This produced an angled hole that would direct air into the drum as you drove forward. I liked to keep the hole spacing around 1.5 to 2 inches circumferentially and at least an inch apart width wise. The holes should be staggered by a division of the number of rows by the incremental angle between holes. thus if you had an 8 inch drum you would calculate hole spacing first (diameter x 3.14=circumference) divided by 1.5 to 2 for the closest even number. Let say 1.5 in this case. that would give you 16.75516 which we will round down to 16 holes to keep the spacing above 1.5". Take 360 and divide by 16 to get your incremental angle of 22.5 degrees. Now divide that again to get the incremental offset of the second row of holes at 11.25 deg. thus you will have two rows of 16 holes with a 1/2 increment offset. For three rows do the same but divide the incremental angle by 3. After all your holes are milled deburr the inside with a round dremel stone. You want to give the holes a nice chamfer. This prevents your new vents from cheese grating the snot out of your shoes. That's how I did it. Others may have better methods or even actual scientific methods to calculate the placement and optimal quantity of holes. Just remember that the drums will need to be magnafluxed if they are used beforehand to check for cracks. You should also routinely check them "visually" to make sure no cracks developed " silver high temp paint makes this LOADS easier". I have had a set of 3 inch wide drums snap the band off the hat, but I was a little ambitious with my venting. If you are running legstrong unobtanium brakes I would steer clear of this mod all together. You will muff some drums up finding the sweet spot in hole placement and quantity. If you decide you want to journey further down the rabbit hole I can tell you how to slot drums as well, but it's a far more complicated process. Posted using the Full Custom H.A.M.B. App!
Thanks for your replies , I was unaware of the potential for the drums to crack or break due to drilling . I guess I shall talk to the lining supplier to see what options are available. Regards
I'm not speaking from experience or anything, but my first thought is to drill the drum the other way around, so the angle of the hole together with centrifugal force would tend to expel air from the inside of the drum. Then all you'd need would be a backing-plate air scoop of the kind often seen on period rods and racers. After all, the idea is to get air flow through the brake: if you can get air in you have to get the same air (which has now expanded due to the heat it's absorbed) out again. And vice versa: if you can get hot air out you have to have a way to let cool air in.
They need no vents in the backing plate thanks to the magic of laminar flow cool air in the front, hot air and crud out the back . Vents are properly used in cars where the aerodynamic properties of the body offer a lack of airflow around the brake components. And as I mentioned before, you can slot them as well. Posted using the Full Custom H.A.M.B. App!
Interesting article on it. I spoke to this guy and got braided hoses from him for my 56 210. He sounded knowledgeable and was forthcoming about his research. http://www.chtopping.com/CustomRod4/
It might be a good idea to replace the flexible brake hoses in the front,,as they age the brake fluid can break down and the inside gets soft,,this can restrict the fluid forcing one wheel to lock or pull prematurely. I learned the hard way. HRP
Thanks for the links , I knew there was some info about , but I just couldn't find it. If Danchuk is selling them , then the potential for cracking drums must be very low , I'm sure they would not want to put their company thru the lawyers mincer . I have managed to source a set of new drums , so they will be a sound basis to do the drilling to and I will do just that. Question .......... what size drill is used for the vent holes , it looks like 3mm or 4mm but the pics are hard to tell. HRP , yep , I've got new flex lines.
1/4 or 3/16 whichever fits the best in your application. Remember to chamfer both sides. Posted using the Full Custom H.A.M.B. App!
when you drill them they reccomend you take a hardened ball bearing and compact the edge of the hole to prevent cracks from starting , we do this when we drill brake rotors for motorcycles and some cars . never had a rotor crack yet . as for relining on some of the bigger trucks we get the newer materials with a semi metallic formula and it works great . and holds up under high heat .
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