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MG MGB Technical - Drilled drums?

Has anybody had any experience with drilled brake drums. That is drilling holes in the friction surface of the drum. Not as many as you see in drilled rotors, but enough to let out water and gasses. Sounds like an interesting idea, especially is some of the wetter climates. From what I've read it seems like the idea came about at around the same time as disk brakes, so it never really caught on. The only thing I'm concerned with is the integrity of the metal as I'm not an engineer, so I wouldn't really know how it is affected.

http://www.chtopping.com/CustomRod4/

http://www.jalopyjournal.com/ubbthreads/showflat.php?Cat=&Board=UBB1&Number=69580&page=0&view=collapsed&sb=5&o=14&fpart=1

-Jared

Jared Snider

Jared - Why would you want to drill the rear drums when at least 60% of the braking is done by the front brakes? I would think that drilling the drums would let water in rather than letting it out, since water doesn't get into the rear drums unless you are in the habit of fording rivers in your B. If you are loosing braking in the wonderfull dry weather of the Pacific Northwest, the problem is the front rotors getting wet, particularly if you have wire wheels. Having driven an MGB in Western Washington State for 15 - 20 years, I can attest to the fact that, if it is raining hard, things can get real exciting the first time that you hit the brakes after driving for any distance on the wet roads. I minimized the problem on our MGB by getting a set of MGOC slotted disks and the "green stuff" kevlar pads. It doesn't completely eliminate the problem, but it no longer takes a "lifetime" for the rotors to dry off and take hold when driving in the rain. It is much more acceptable when trying to stop in a hurry. Good luck - Dave

PS As I remember, the MGOC also offers slotted rear drums for the MGBs.
David DuBois

Jared. Like Dave, I grew up in the era of drum brakes all the way around. When driving in Orlando, where street drainage in the 50s and 60s was not great, but there was a lot of rain, the habit was to left foot brake when driving through the standing water. Water in the drums cut the brake effectiveness significantly.

It would seem to me that drilling holes in the periphery might tend to allow water to be thrown out of the holes. It would also, allow water to get inside the drums more easily and wet the interior. It might also allow more road grit inside, causing faster wearing of the drums and linings. I remember a number of the rally cars, sponsored by BMC having special, finned brake drums, but do not remember any having drilled drums. Based on these factors, I would not use them on my daily drivers. Les
Les Bengtson

Drilling the drums would have one benefit, weight saving, but it is so minimal that it would be better to have finned drums that can be lighter, but stronger, and offer quicker cooling than standard.
FWIW
Martin

An interesting idea, but several things immediately come to mind:

1) I would imagine that this would require very precise drilling in order to maintain rotational balance
and strength (to avoid warping, cracking, etc.).

2) As Les had already pointed out; any water, mud, etc. splashing onto the drums could work it's way
down inside the brake assembly. Not good ...especially if you encounter the need for a rapid stop
during rainy conditions or just after a healthy car wash.

3) If it's dissipating hot gasses and shedding water from the brake shoes that you want...many old-time
racers would cut thin grooves across solid (ungrooved, unsegmented) friction material on the shoes
using a hack saw. 2 grooves per shoe, evenly spaced. Keep in mind that cutting grooves across
the shoes takes away some friction material that make contact with the drum, so DO NOT be
tempted by the 'ol "More Is Better" rule-of-thumb. DO NOT cut all the way down to the brake shoe
backing metal. Leave about 3/32" - 1/8" of friction material untouched.

Some aftermarket brake shoes already incorporate grooved or segmented friction pads on them.

4) During wet conditions ...just slow down, and increase your following and braking distances.
Daniel Wong

Probably the better solution over drilled drums would be the slotted or grooved ones as mentioned above and sold by the MGOC and others. I cannot think that holes in the drums would carry any great benefit even with respect to water ingress.

However i would have thought that if you spend your money/time on the front brakes (getting them set up correctly, perhaps considering a 4pot conversion) you would not need to alter the drums from standard at the rear...

I looked at the grooved drums when upgrading my car's braking system, but i considered them more for show than anything. I have not found anything yet to say how useful they would be, given that most braking effort on the B is done by the front wheels. Anyone running a bias brake valve would probably have a rear disc conversion anyway.

JMO ~PHIL
Phil

Jared-
The MGOC sells slotted brake drums. They allow for venting for gases when the shoe materials get really hot.
Steve S.

Daniel - My one thought to "slowing down when it rains" in the Pacific Northwest is that we would all be doing 45 MPH on the freeways up here 9 months of the year.
Cheers - Dave
David DuBois

This thread was discussed between 27/05/2003 and 28/05/2003

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