Hello,

I understand why the Rocky Mo. brakes do not work in reverse. Self-energizing. I have worked with band brakes before.

What I need someone to do is explain what scientific process is happening when the brakes get wet and they become almost useless.

Disc brakes work when wet. Drum type brakes work when wet. Maybe not as well, but they work. But my Rockies do nothing to stop the car when their wet.

How can just water render them useless?

Steve

Water is a very good lubricant. It 's just corrosive.

I have had shoe brakes that would not hold at all when they were wet. Used to drive with foot on brake to keep them dry. It did not happen in a drizzle but when it was raining pretty hard. I suspect they have improved the linings in recent years as I have not noticed it in recent years. The only thing I hahe with shoe brakes is my 38 Buick. Nelson

I have had shoe brakes that would not hold at all when they were wet. Used to drive with foot on brake to keep them dry. It did not happen in a drizzle but when it was raining pretty hard. I suspect they have improved the linings in recent years as I have not noticed it in recent years. The only thing I hahe with shoe brakes is my 38 Buick. Nelson

Shoe type brakes typically do not get wet in just a rain since the drum and the backing plate are designed to keep water out to a certain extent. What usually happens is that if you drive through standing water that is above the bottom of the brake drum then water floods into the drum and then you typically have ZERO brakes until the water drains out and the shoes are dried out which can be speeded up by hard application and eventual friction bringing some heat to bear but for awhile - it is fun driving. I think the basic difference in disc brakes might be the fact that the pads can quickly strip the water away and centrigal force and gravity also pull the water off unlike drum brakes where the water really is forced to the outer diameter and makes it kinda hang there. I have not looked at Rocky Mountain brakes per se but strap brakes also do not quickly rid themselves of any water that gets into them since it is a continuous strap and there is no real stripping action like with the discs. I suspect that brake band material selection also plays a part in this since by their design the band has to be somewhat pliable while disc pads can be hard as a rock. I could be all wet in my understanding of this (pun intended).

I have the earlier style Rocky Mountain brakes on our 13 touring. They have the advantage of having brakes in both directions vice the later style. However, in the forward direction the later style stops quicker....I can not skid my tires using just the RM's. I also have cast iron drums which may work better than the formed style. They are much thicker and have more material to dissipate heat. Regardless, when they get wet...they do not stop very well and I must rely on the internal band to do most of the breaking until the RM's dry out. I have the internal brake band adjusted loose so it works only when the pedel nears the floor.
I like the way the disk brakes work....but do not like their modern look. Wished there was disk brakes available that would fit inside the drum where the emergency brakes are.

This is why you should always have BOTH the Rocky Mountain brakes and the transmission band brake working and properly adjusted at all times. You should also have the Model T rear brake drum brakes adjusted properly and working.

I don't know who started the idea that if you have Rocky Mountain or Bennett brakes you can disconnect or ignore everything else, but it is a dangerous delusion.

I always thought the hydraulic brakes work better because of higher pressures involved.

I keep all my brakes adjusted including the reverse pedal and the low pedal. One advantage of living in California is that we typically go about 9 months with very little rain. We have about one short thunderstorm usually in August. But from the last part of December until the first part of April it can rain at any time. But typically don't drive the T's in rain unless we just happen to be caught by surprise. There is one other factor in rain driving and that is especially dangerous in a climate like ours with such a long dry spell. The first rains tend to float the oil to the surface of the road and make it very slick. This is especially hazardous with 2 wheel brakes but even the modern cars tend to slide and many accidents occur.
Norm

Hydraulic brakes have higher pressure involved??? Why is that?
A '39 Ford with brakes PROPERLY adjusted takes no more pedal pressure to stop than a '39 with hudraulics.
Internal brakes with two shoes have four ends. That leaves two ends on leading edges wiping the water off the braking surface-what little water that gets in.
Shoes usually fit the drum a lot better than outside bands too.
They used to say we needed shoes and drums on the back in our modern cars so we could still stop when the brakes were wet.
Disc brakes don't stop you as well when they're wet untill the wheel goes around a few times. Remember too, those discs are usually pretty hot when driving in town, that helps keep them dry.

Sorry, my mistake, '38 Ford has mechanicals, not '39.

I don't know about Rockies, but my TT has Bennett brakes. The Bennett pedal is made absent the cam needed to operate the transmission brake. How does that fit into this discussion? It would seem that the manufacturer, for some reason, decided that the transmission brake was not needed when the truck was equiped with the Bennett brakes.

By the way, I'm not being critical at all, just curious. I have always believed that stopping is a much bigger problem than going!

The question was regarding Rocky Mountain brakes. So far as I can tell there are no Rocky Mountain brakes that are hydraulic.

The Bennett pedal I bought from Chaffins has the cam that operates the stock brakes. No problem hooking it up and making it work properly. Here's what mine looked like:

Disc brakes can fade when run through enough water too. I find the problem usually occurs as I exit an automated car wash of the type where the car is on a conveyor and we take advantage of the "under body wash" option. Up here (Minnesota) it's worse in the winter because it forms ice on the rotors. Luckily, it's about 80' to the street from the end of the car wash which is just enough time to "set the binders" and clear up the problem. Some makes can be worse than others. My '95 Saturn was always a challenge.

Royce - That's very interesting. Thanks for posting the photo.

I checked mine and there is no cam and it does not look like there ever was. No evidence of grinding or cutting. I wonder if they were made differently for regular T's than for TT's. Or, maybe they were made differently as they evolved over time.

On the older brakes you did not have to drive through standing water to have the brakes not hold. As I said it did not happen in a drizzle but a good hard rain would cause you to lose braking. Nelson

Maybe they should call them "Sunshine Brakes"?

en.wikipedia.com to read the whole thing:

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Vehicle braking system fade, or brake fade is the reduction in stopping power that can occur after repeated application of the brakes, especially in high load or high speed conditions. Brake fade can be a factor in any vehicle that utilizes a friction braking system including automobiles, trucks, motorcycles, airplanes, even bicycles.

Brake fade is caused by a buildup of heat in the braking surfaces and the subsequent changes and reactions in the brake system components and can be experienced with both drum brakes and disk brakes. Loss of stopping power, or fade, can be caused by friction fade, mechanical fade, or fluid fade. Brake fade can be significantly reduced by appropriate equipment and materials design and selection.

Brake fade occurs most often during high performance driving or when going down a long, steep hill. Owing to their configuration this is more prevalent in drum brakes. Disk brakes are much more resistant to brake fade and have come to be a standard feature in front brakes for most vehicles...

.......

Drum brake fade can be reduced and overall performance enhanced somewhat by an old "hot rodder" technique of drum drilling. A carefully chosen pattern of holes is drilled through the drum working section; drum rotation centrifugally pumps a small amount air through the shoe to drum gap, removing heat; fade caused by water-wet brakes is reduced since the water is centrifugally driven out; and some brake-material dust exits the holes. Brake drum drilling requires careful detailed knowledge of brake drum physics and is an advanced technique probably best left to professionals. There are performance-brake shops that will make the necessary modifications safely.
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rdr

Boy, all those hoop stress problems from my strengths of material classes are flashing in front of my eyes. I didn't understand it all that well back then. I'm sure not going to try to go through them now. Does make sense though, provided you have enough strength left in the drum.

Henry Petrino,
I like to use the original pedal and weld an arm to it. The RM pedal is cast iron and I have heard that some have broke. One friend that this happened to said there was a casting void inside the pedal and that is where it broke. An internal cast void is only detected by X-ray. I trust old Henry's pedal material far more than a cast pedal. This is assuming the weld is done right with good penteration.
The older style RM pedal did not have a cam to allow using the internal brake band.
I also use lined emergency brakes.
Suggest replacing your pedal and installing another brake band.

Actually, Aaron you were right. If memory serves me correctly, 1939 Standards had mechanical brakes and 1939 Deluxes had hydraulic brakes.

I can't speak for the rest of the world, but all 1939 Fords produced in North America had hydraulic brakes. This included the trucks and the standard car line as well. The mechinical cable brakes were all phased out with the end of 1938 production.

Was 1939 when the main patents expired?

In Germany in 1967, my 1950 VW Standard daily driver had mech brakes. I never messed with them, but they were a harder pedal than my 1951 Deluxe with hydraulics. That was the only difference I noticed.

rdr

I was told by my dad, teachers and Missouri Highway Patrolmen in my driver's ed course (back when they taught such things in school) that after you drive a car, any car through water, you should lightly apply your brakes and let friction heat the brake shoes and heat the water out of the drum, rotor.
My '26 roadster uses an equalizer and the original brake drums as service brakes and I do this wet or dry from time to time and the brakes work well.
I was also told there is a small percentage of drag on disc brakes to prevent the problem of water lubricating the brake pads. A recent car commercial, Lexus I think, bragged about the "idiot proof" disc brakes where the computer would drag the disc brake shoes for the driver who should do the job when the computer sensed rain.
Believe me, the same water to brake pad problem works the same way with railroad trains and can provide even more pucker power in the process.

Joe R.