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Drilling brake drums for quick dryouts.


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Due to the shape of my portal boxes I am pretty much stuck with drum brakes on my truck unless I cast my own calipers. No problem really,after 40 years of series ownership I've learned not to depend on brakes that much, and the 11'' x 3'' do last a heck of a long time between relines even when regularly exposed to deep mud. Stage 1 oil catchers around the hubs stops any oil from hub seals contaminating the brake linings, and hose clamps on the wheel cylinder boots prevent brake fluid doing the same. The only problem. if it could be called that, I have is that it takes an inordinately long time to dry the brakes out after fording streams etc.This is a similar thing to brake fade except that we have a film of water between the shoes and the drum surface acting as a lubricant instead of a film of hot gas. I have been toying with the idea of drilling a few holes around the braking surface (swept area) of the drums to help disperse the water/gas film, but because my truck is also used daily in peak hour traffic I'd prefer to avoid any disasters due to exploding brake drums caused by the holes I drilled. So my questions for possible discussion is, Has it been tried before ? what were the results ? How many holes if any should I drill and how big? Would drilling the brake shoes acheive the same ends ?

I did read some years ago of a bloke in the US with an early Bronco who changed from 4 wheel discs to 4 wheel drilled drums, claiming superior all round braking performance, but the article didn't go into detail.

Bill.

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I'm sure I've seen drums where the junction between the face and friction surface was bevelled with drain holes drilled in the bevel. I think there were three holes about 2mm diameter each.

Yes, those drain holes are small and block up easily with mud. I opened them up to 1/2'' dia years ago and it helped a little.

I've just drilled 4 equally spaced but staggered holes in one of my front drums to experiment with. I'll flood both brake assemblies with the garden hose and go for a drive to see if that side dries out quicker.

Bill.

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Bill,

I am pretty sure that someone once explained the brake set up on logging trucks in Malaysia for me. These are all drums and as you may know, they actually have a water spray set-up to cool the brakes as they descend from the Central Highlands. As I recall, the drums were both grooved and drilled to aid in both cooling and the removal of the water. As you can imagine, these trucks are exposed to quite a bit of mud! Now, I wouldn't suggest grooving your drums as there is no telling how much that would weaken them, but I think you could certainly drill them without running such risks. I would imagine that with your ingenuity and fabrication skills, you might even sleeve the drill holes to be extra safe!

On the disc question, what is the chief obstacle to grafting on calipers? I have been quite impressed with the Portal-Tek disc brake kit for C303 axles that uses Wilwood discs and low profile calipers. Admittedly, I had to have new wheels custom made as they would not fit within the Volvo 16" wheel...

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If you're going to groove the drums, why not just one groove in the form of a single spiral so it pushes water out to the edge of the drum?

The outer end of the spiral could terminate in a hole, the inner will push crud off the edge of the drum.

The spiral would be formed so that the muck is forced outboard when going forwards.

A spiral would also avoid wearing ridges on the shoes.

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Thanks guys. Richard,I would have thought engine brakes may have superseded the old watercooling system of logging truck braking systems by now. Certainly a lot less Australian logging truck drivers meet their maker early since the introduction of engine brakes.The Volvo portal boxes are sort of teardrop shaped, allowing the caliper to be positioned in a more or less standard, or above centre location,where as the sides of my portal boxes are parralell and quite wide, which means the caliper would need to be mounted at the bottom, which I think is unsatisfactory and leaves the plumbing vulnerable to damage. My experiment yesterday with drilling holes in one brake drum was inconclusive due to the difficulty in flooding the brake assemblies with the garden hose. Tucked well inside the deeply backspaced wheels 11''x3'' brake assemblies are well protected and its not easy to soak them without submerging them in a stream or similar. Not many streams in suburbia so I'll try again when I go bush on the weekend. After drilling the holes I am no longer concerned about drum failure. They are very substantial. I don't really have the facilities to make a neat constant depth spiral with my trusty angle grinder, but holes I can manage, and I have plenty of spare drums if I screw up. I may be the odd man out here but some years ago when my truck had conventional axles and 4 wheel discs I was a little underwhelmed by their stopping ability, particularly in situations when vacuum fails due to a stalled engine on a steep precipice.my drums don't need and don't have servo assist. I have grown out of the phase where I tended to plunge into every mud hole I could find, so I think I'll persevere with the drums and try to sort the slow dryout issues.

Bill.

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This is a topic I will try ot follow closely.

I have 15" wheels on my Volvo's so discs are more or less out of the question and I'm not prepared by a long stretch to change brakes, wheels and tires.

I still have not flooded my brakes to the extent where I've felt the loss of brakes, but I'm sure it exists and would welcome any mod to improve drying.

Turning a groov would seem quite easy if you have access to a lathe.

But let's hear some experience with the holes first.

Tobias

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In th 80's I had a '84 Suzuki RM 125 that was a pre-disc model, it had a twin leading shoe arrangment on the front that was probably better than some of the first disc attempts, about mid to late 80's EBC brought out a range of brake shoes for this age of bikes that had grooves in the linings, I had a set and they were extremely effective, the groves went as deep as the minimum wear for the linings, not all the way through to the metal.

Andy

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In th 80's I had a '84 Suzuki RM 125 that was a pre-disc model, it had a twin leading shoe arrangment on the front that was probably better than some of the first disc attempts, about mid to late 80's EBC brought out a range of brake shoes for this age of bikes that had grooves in the linings, I had a set and they were extremely effective, the groves went as deep as the minimum wear for the linings, not all the way through to the metal.

Andy

I had actually thought about drilling holes in the shoes, but was concerned about upsetting the shear strength of the bond. apparently the old style riveted brake linings were reputed to fade less than bonded linings.

Bill.

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Volvo made a wading kit for 303s, its an ally wear ring and a wonderfully ornate seal with ball bearings moulded into the rubber to prevent the rubber from frying, the breather hose on the back plate can be fed with positive pressure to keep nasties out

in reality once the seal cracks (doesnt take long) the drums fill with pooh and then drain out even slower than before :lol:

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Hi bill,

My callipers are mounted at the bottom of the portal box and so far i've had no problems with damage or vunrability.

Hi Dan, I'm surprised to hear that. But I suppose because the brake assemblies are a long way inside the wheel rim they probably are quite protected. Must have been the pics of Maxidrive portals and brake assemblies with standard offset rims that put me off having calipers at the bottom.

Jez, is what you described, the so called centrifugal brake seals that supposedly come into play at speeds below 15 mph, I read about on a contemporary road test on Volvo c303 in the mid 1970's ? None of the ex Malaysian military Volvo axle assemblies I've played with had any remnants of that arrangement save for some tags spot welded onto the backing plates.

Bill.

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Hi Dan, I'm surprised to hear that. But I suppose because the brake assemblies are a long way inside the wheel rim they probably are quite protected. Must have been the pics of Maxidrive portals and brake assemblies with standard offset rims that put me off having calipers at the bottom.

The calipers are quite well protected by the wheel, but visually they look vunerable esspecially the brake pipes but despite my very best efforts they've suffered no damage to date.

Me too - usually if Dan's driving every part of the vehicle is vulnerable to damage! :lol:

John, you've only seen the damage charlotte can do under my direction, just imagine what i can do on my own :D

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The calipers are quite well protected by the wheel, but visually they look vunerable esspecially the brake pipes but despite my very best efforts they've suffered no damage to date.

Your wheels are almost fully backspaced, do you think that you would suffer more damage if using a rim with a wider offset?

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Your wheels are almost fully backspaced, do you think that you would suffer more damage if using a rim with a wider offset?

7" rim running 2" offset, so not fully back spaced.

But other than a bit of a guard for the brake pipes (as fitted to steves car) i think the g wagon calipers are man enough to look after themselves.

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I think the G Wagon calipers are man enough to look after themselves.

Accepted. However, if using another caliper would you be more concerned for their longevity?

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  • 2 weeks later...

According to a chap at X-Eng, best place to drill is the angled front of the drum, near the braking surface. Four or six holes 1/4". Lets the water centrifuge out without weakening the drum.

Entirely with you on discs - waste of space. My drums gave 92% efficiency on the rollers at the last MOT. And no servo.

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Entirely with you on discs - waste of space. My drums gave 92% efficiency on the rollers at the last MOT. And no servo.

I don't think anybody is disputing that they do the job under normal road conditions, it's more the fact that get them full of wet sloppy stuff and that 92% flies out the window as fast as you do whilst expecting the brakes to slow you. Well that's what happens in my experience anyway.

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