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Old 09-02-2021, 11:20 AM   #11 (permalink)
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We have them here on logging trucks, sometimes, but as a last ditch effort to save the bacon of the driver driving way too fast for the load. I've followed one tanker that was misting my windshield on the 80 to Sacto outside of Colfax until I passed it.

The only issue with retarders is that they require prediction not reaction. Once you've oversped on downhill, it's too late. Typical driver would fail the prediction.

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Old 09-02-2021, 01:52 PM   #12 (permalink)
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When I drove school bus over the mountain passes for games and such the mechanic said he never had needed to change a bus brake.

All the buses had drum brakes both front and back. These vehicles were rated for over 35,000lbs GVWR. They also all had an electromagnetic eddy current retarder that worked wonders IMO. Of course we all were also trained to downshift and keep our speed under control. Between the retarder and downshifting none of the bus drivers ever needed (or need still) to use the mechanical brakes.

Decades ago there was a bus that had once lost it's brakes going down Monarch Pass and several children died. From what I understand, that influenced the driver training and retarder choice after that.

The same mechanic said at one point he was changing the disk brakes on the company sedans nearly every trip because the teachers didn't know how to downshift going down mountain passes and would warp the rotors. So eventually he changed all the company car brakes to oversized drilled and slotted racing rotors with large ceramic brake pads. After that, the cars didn't come back with warped rotors all the time.

My Conclusion
Drum brakes work. The vehicle may need and benefit from other types of braking, even if it's just engine braking. But that braking must be applied, and with so many drivers out there that don't have a clue what the numbers past PNRD mean it's probably best to impliment downshifting as an automatic feature. That or regenerative braking.
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Old 09-02-2021, 03:57 PM   #13 (permalink)
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You can drill brake drums as well.

Quote:
Drilled Drums - CH Topping Brakes
Drilled Drums
Project Plymouth gets a decades-old brake trick… Drilled Drums Text by Dave Hill / Photos by Jerry Weesner and Dave Hill . What's the first thing you think of when considering updating your '50s cars brakes? Discs of course. There are many ways of adapting discs these days, the easiest of which is ordering a kit from one of our advertisers.

Drilling Brake Drums | The H.A.M.B.
https://www.jalopyjournal.com/forum/...-drums.165001/
The Herb Adams mod consists of drilling five 1" holes in the face of the drum on the flat areas between the studs and outboard of the stud circle. The backing plate is also drilled. This uses the motion of the drum to pump air through the brakes and help cool them. The modification instructions never mention drilling the braking surface of the ...
That really helps if you drive through standing water.
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Old 09-02-2021, 06:36 PM   #14 (permalink)
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Cost, weight, and heat transfer determine the choice of braking systems. I sold auto parts for 10 years after studying engineering so I got real familiar with all types of vehicles. The materials play a big part.
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Old 09-03-2021, 01:44 AM   #15 (permalink)
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I remember some claims about Russian cars with aluminium brake drums to be less prone to brake overheating (and ultimately fading) than a Western counterpart with cast-iron drums for instance.


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Originally Posted by Isaac Zachary View Post
When I drove school bus over the mountain passes for games and such the mechanic said he never had needed to change a bus brake.

All the buses had drum brakes both front and back. These vehicles were rated for over 35,000lbs GVWR. They also all had an electromagnetic eddy current retarder that worked wonders IMO. Of course we all were also trained to downshift and keep our speed under control. Between the retarder and downshifting none of the bus drivers ever needed (or need still) to use the mechanical brakes.
One night an interstate bus driver told me he could go from Porto Alegre to Florianópolis and keep the feet away from the pedals most of the time, not only due to the adaptative cruise control and automated transmission but also due to engine-braking and retarder.


Quote:
Decades ago there was a bus that had once lost it's brakes going down Monarch Pass and several children died. From what I understand, that influenced the driver training and retarder choice after that.
Training is always important for drivers to take benefit from some feature of a vehicle, but it's been taken more seriously when it comes to commercial vehicles, while the average Joe looks at any car in some sort of one-size-fits-all perspective.


Quote:
The vehicle may need and benefit from other types of braking, even if it's just engine braking. But that braking must be applied, and with so many drivers out there that don't have a clue what the numbers past PNRD mean it's probably best to impliment downshifting as an automatic feature
Reminds me the day I downshifted in a Hilux that my grandfather used to have. He claimed to not have even tried it because he feared it could increase the chance of a rollover


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That or regenerative braking.
One aspect that made me look into Toyota's hybrid system as quite likely to replace a traditional automatic transmission is exactly how the regenerative braking feature acts in a similar way to electromagnetic retarders.
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Old 09-03-2021, 03:25 AM   #16 (permalink)
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Quote:
I remember some claims about Russian cars with aluminium brake drums....
Quote:
Pontiac 8 Lug Wheels - Pontiac Paradise
Pontiac 8 Lug Wheels
Kelsey-Hayes started making 8 lug wheels for Pontiac for use on 1960 full size Pontiacs. The were finned aluminum and were very good at keeping brakes cool. Cool brakes make big cars stop faster! The first drums made had very short and steep fins. These drums were used up thru 1962.


Wide eights! Much cooler than the Buick finned aluminum drums.



www.speedwaymotors.com/Buick-Style-Finned-Aluminum-Brake-Drum-for-Ford-Spindles
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Old 09-03-2021, 06:47 AM   #17 (permalink)
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drum brakes are usually lighter than a disc, the caliber and associated brackets needed to mount the caliber. My Tacoma has rear drums.
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Old 09-03-2021, 06:08 PM   #18 (permalink)
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Quote:
Originally Posted by Vwbeamer View Post
drum brakes are usually lighter than a disc, the caliber and associated brackets needed to mount the caliber
Not totally sure if this applies to all vehicles, yet I also don't remember to have ever seen any disc brake made out of aluminium for instance.


Quote:
My Tacoma has rear drums.
Even though the Tacoma is not sold officially in my country (privately-imported ones show up once in a while), where since 2001 the Hilux is the only Toyota truck available, it's no surprise it has rear drums. Just like the Hilux and most other Toyota commercial vehicles within a similar size bracket.
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Old 09-12-2021, 05:26 PM   #19 (permalink)
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i think it also has to do with car makers wanting to make more money, modern cars with disc all round often need rear discs replaced and rear brakes serviced, cannot remember ever having that problem with rear drums

rusty rear discs anyone?
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Old 09-12-2021, 07:35 PM   #20 (permalink)
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Quote:
Originally Posted by SkauneJohan View Post
i think it also has to do with car makers wanting to make more money, modern cars with disc all round often need rear discs replaced and rear brakes serviced, cannot remember ever having that problem with rear drums

rusty rear discs anyone?
I've never had a problem with rusty disc brakes.

Both of my 2nd gen Prius had an issue where they would rust after a rain and during the first stop they would lock momentarily with a crunch at 7 mph. (The Prius switches from regen to friction brakes at 7 mph) To solve this I would put the car in neutral for the first brake after a rain storm (which turned off regen) and would brake with friction brakes to clean things up. Braking down from 25 mph was enough to clear off the rust in one stop. From then on everything worked fine.

I also had one of the Prius rear parking brakes freeze in the on position in cold weather. The road was slick enough their wasn't enough friction to break it loose so it stayed locked for about a mile. That lit up a bunch of warning lights!

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