Brake fades if hot

[Werner]

Hi, I have very much brake fading, if they get hot.

Is this normal that on steep downhill driving after about 1/8 ml the brakes are so hot that there is only a very little braking power?

The brake linings and the mechanics I have completely renewed / revised. The contact pattern of the friction shoes on the drums are good.

But all 4 brakes get so hot after this short time that I can no longer touch them. Spit against evaporates.

[Ruth]

Do you have the original steel brake drums or cast iron brake drums? My brakes would fade when I was just driving around town until I switched out to cast drums. The problem is that the outer part of the drum expands so the lining only touches the inner part of the drum. (the side where the hub attaches). This becomes more pronounced after the drum has been turned a few times (which Ford recommended not to do).

Cast drums made all the difference in the world.

I got my drums and shoes from Randy Gross in California but he is a little far away for you. [email protected]

[Ivan in southeast va.]

You need to let the engine help you do the braking on a long steep decline. When coming down a mountain you need to be in a lower gear. Without synchronized gears it's hard to down shift when coming down too fast. Ask me how I know.

[fastroadster]

Listen to Ivan... don't ride your brakes, of course they will fade out. Gear down, your're not in any race. Go at your own pace.

[denis4x4]

I installed the Rocky Mountain brake bands that worked for awhile. After blowing through a stop light in Scottsdale as the brakes faded, I switched to hydraulics on three of my A’s and never looked back. I don’t care if you can “skid” all four tires with properly maintained mechanical brakes. I drive my cars in traffic and there’s no room for error.

[Werner]

Sponsored Links (Register now to hide all advertisements)

Good evening,


thank you all for the feedback!

There are brake drums that are cast iron.

Correct, downhill the engine brake helps very much. But when I'm sliding down in the 2nd gear, I'm very slow because I don't want to over rev the engine more than 2000 RPM.

In Germany, the road traffic is very dense! The drivers behind are impatient and especially black Audi/BMW/small Mercedes with loud roaring exhaust are aggressive drivers.

But back to the subject, I understand correctly that the pronounced fading is normal. Then I can not improve something mechanically, but must adjust my driving style slower.

[ursus]

I am sure aggressive driving is not unique to Germany! This is the greatest concern I have with driving a Model A in dense traffic. Even with good brakes it takes extra attention to stay out of trouble. This situation seems to have worsened considerably since I bought my first Model A 40 years ago.

[Patrick L.]

I wonder of the 'rocky mountain' drums would help.

[Gene F]

Are rocky mountain drums cast iron?

[nkaminar]

Werner,

Some bumper stickers available here in the States:

"Not so close, I hardly know you"

"Back off" with a cartoon of Yosemite Sam holding two pistols

"I am not in your hurry"

"Sorry for driving so close in front of you"

"This is not a race car"

"Thank you for not tailgating"

"Get off my ass"

There is more but you get the idea. I have a car camera in my back window that records any car behind me. In case I am hit from behind I have the evidence.

[J Franklin]

I wonder how juice brakes will solve brake fade?

[Synchro909]

Werner, as a rule of thumb, you should always descend a hill in the gear you would use to climb it and keep your foot off the accelerator. Let the engine do the braking and use the brakes only as a "top up".

[bbrocksr]

Originally Posted by J Franklin

I wonder how juice brakes will solve brake fade?

Hydraulic brakes apply more force to the shoe. no lost force on all the pivots ,levers, bellcranks, bushings and wedges, rollers and pins.Plus they're self equalizing.
They won't solve the fade, but will give you much better brakes before they fade.
Bill

[updraught]

Bigger drums, more metal to absorb the heat, more surface area to cool.
The first Holden here came out with disc brakes in the mid 60's with small discs. If you had a hot motor in it on a mountain road, when you stopped the heat was such it would make the grease drip out of the ball joints.

[Richard in Anaheim CA]

Werner,

Friction is what causes the car to slow down. Friction creates heat. Your brake drums are doing their job.

Driving technique can minimize brake fade.
1. slow down before you start down he hill.
2. Make sure you are out of overdrive and transmission is in gear.
3. Make sure your hand throttle is all the way up and your foot is OFF the gas pedal and OFF the clutch until you are off the hill.
4. Let the engine compression regulate your speed.
5. If your speed increases too much apply the brakes FIRMLY to bring your speed under control then get OFF the brake to allow the drums to cool until your speed is again too fast.
6. Repeat #5 as needed. DO NOT RIDE THE BRAKE PEDAL. (verboten)

Richard
Anaheim CA

[1crosscut]

What type of brake pad material do you have on your shoes?

[nkaminar]

I have a Mitchell overdrive in my car and when descending a long hill I will be in second overdrive and switch to second direct when needed. The Mitchell overdrive is synchronized so switching from overdrive to direct and back to overdrive is easy. My car is a heavy Fordor.

Disk brakes are much more fade resistant because of the way they dissipate heat. I had disk brakes on my Model T and would ride them down a steep grade without fading. I cannot find disk brakes for a Model A without changing out the spindles and rear axle and using different wheels. It would be nice if a kit was available that used mostly stock parts.

[Charlie Stephens]

How far oversize have your drums been turned?

Charlie Stephens

[Werner]

Guten Abend Richard & Dave,

yes, the way that Richard ("Dick"?) writes is the way I drive. But as written, the otherwise if cold good deceleration values drop a lot very quickly because the heat is dissipated too poorly.

Dave, in the rear I have mounted the bonded pads that Don Snyder III offers. In front, a specially made and grinded of the measure to the drum size, relatively soft brake pads are glued, which are used for industrial machines; they have an increased coefficient of friction.

btw.: Thanks at all for the helpin' hints!

[ericr]

man, Model 'A" brakes certainly occupy an inordinate amount of attemtion in the Barn!

after reading Werner's comments, do you guys think what he is using for brake shoes on front or rear is an issue? I understand his analysis and don't wish to second-guess him but how often have we seen modern-style improvements to original designs complicate performance?

[Flathead]

Originally Posted by J Franklin

I wonder how juice brakes will solve brake fade?

Yeah, I was wondering the same thing.

[Werner]

Originally Posted by ericr

man,

after reading Werner's comments, do you guys think what he is using for brake shoes on front or rear is an issue? I understand his analysis and don't wish to second-guess him but how often have we seen modern-style improvements to original designs complicate performance?

Erich,

what you write is not to be dismissed. But in this case, I let the pairing of the new pads made with match the material of the drums, namely cast iron.

The brakes grip well, that's why they get very hot. But they have a very strong fading.

I think, as also noted above writers, that is also normal for the large drums. It only happens when I make very steep descents, as is typical here in the Eifel and the Ardennes. I can't name a comparable terrain in USA because unknown.

[updraught]

"With brake fade, the pedal still feels normal, but the vehicle is not slowing down as you would expect. You’ll typically be able to smell the brake pads overheating, and though the brakes are applied, the vehicle isn’t stopping well. The friction created by the brake pads and rotors is used to slow the vehicle. This friction or effectiveness tends to increase as the braking temperature increases, but above certain temperatures the brake pads begin to break down. Gasses can be released as the brake pad material breaks down, these gasses form a microscopic layer between the pad and rotor reducing friction. This decrease in braking effectiveness is considered brake fade."
https://www.powerstop.com/brake-fade...ke-fluid-boil/

I guess you would smell this.

[bavArian]

Has anyone here tried cutting diagonal grooves into the brake pads? I'd suppose 1/32 inch width grooves with a pitch of 3/4 inch should help at least a bit?

[SAJ]

Updaught's post is why I always press and release the brakes on long downhill runs. This releases the gases that form from thermal decomposition of the phenolic bonding agent used in most moulded linings. The result is better braking each time the pedal is quickly released and re-applied, that you can easily feel.
Possibly the grooves bavARIAN mentions might help, but there will still be a trapped layer of constantly reforming gases in the contact areas between said grooves.
I have always felt moulded linings have more resin than woven, which need less adhesive to hold the friction media together due to the mechanical interlocking of the weave. And hence woven off-gas less than moulded on long downhill runs,.
Just my opinion.
SAJ in NZ

[Werner]

Sponsored Links (Register now to hide all advertisements)

Guten Tag.


I think that the main cause of brake fading does not depend on the gas layer, but that the friction coefficient between the friction lining and the drum decreases more and more with increasing the temperature.

Because that is the physics. The energy of the accelerated car mass must be decelerated by the friction brakes. The friction generates a lot of heat. The higher this temperature of the drums and the linings becomes, the more difficult and slower is the dissipation of the heat. As a result, the temperature continues to rise and the coefficient of friction decreases until at some point there is hardly any frictional force left.

Modern disc brakes are therefore additionally ventilated from the inside.

And this is why the old racing cars with drum-brakes used many cooling fins outside on the drums.

[Flathead]

Energy can neither be created nor destroyed, if I remember correctly from Physics class. Therefore the energy of motion is converted into heat by the brakes, the brakes need to transfer this heat into the air which is left behind as you speed down the hill. The more mass the brake drum has the more heat it can absorb, new cast iron drums are heavier than the thin steel originals that have likely been resurfaced even thinner over the years. Fins would help to get heat out of the drum faster by increasing the surface area exposed to the air. When the drum gets super hot it will expand into a slight bell shape that hinders good shoe contact, but at that point it probably doesn't matter much. The only way hydraulic brakes will improve a fade problem is if the conversion includes larger finned drums, and that is about drums not hydraulics.

[Werner]

That's exactly the thing, how you describe it. However, it takes longer for heavy material drums to cool down.

I'm surprised that no other A-drivers, that lives in the mountains, has written that they also has fading. Because I do not think that I'm the only one with this brake heat problem.

A good solution would be to enlarge the drum surface with a corrugated aluminum ring sitting tightly on the drum or to put cooling fins with MS-hard solder on the drums. Neither is easy.

I am also surprised that these accessories are not available for purchase to my knowledge.

[Vic in E-TN]

Werner is correct in that the coefficient of friction decreases with temperature. I looked at the German chart that he posted. Although I cannot read German I can look at the first small chart which shows Coefficient of friction (COF) vs. temperature and it shows a drop from 0.42 at 100 Deg C to 0.34 at 300 deg C (572 deg F). I am not a brake engineer but this material looks pretty good relative to fade. Randy Gross says that his material for the last 15 years is unclassified but is suitable for slower cars that do not travel more than several thousand miles a year. Don Snyder does not provide any information to Werner. In my opinion Randy Gross's lining material is superior to Snyder's brake linings for our cars. I would like to discuss this subject with Walt Bratton and Steve at Bert's. If I can get more information I would like to submit an article to one of our club magazines.
Vic

[Synchro909]

Originally Posted by Flathead

Yeah, I was wondering the same thing.

Hydraulic brakes will fade just like mechanical ones. I used to drive a 1967 Toyota. Brake fade was a part of the "character" of that car. I don't know how many times I had both feet on the pedal and my backside off the seat.
Another property of drum brakes is that as they heat, the drum expands and the pedal goes down. With external brakes, you adjust them so that they start working with the pedal near the floor. As the drum expands, the pedal rises. If they are adjusted like drum brakes, they would expand to the point where they are locked on and you must wait till they cool before being able to move again.

[Pete]

See if you can find "Velvet Touch" lining that can be adapted to the model A brake shoes. It is a sintered bronze metalic type lining. It IS still available somewhere.
The hotter it gets, the better it works. I have seen the drums red hot on race cars with it and still worked good.
I used it on my service truck for years. On the street it seemed like it lasted forever.