Would a modern car with drum brakes all-around still have a chance?
 

I'm sure most people have already been totally convinced that disc brakes may be inherently "superior", even though economy cars and some trucks still resort to drum brakes at the rear-end. But it's worth consider how drum brakes retain a foothold on the heavy-duty truck market, even though it's most noticeable on models meant to feature off-road capability.
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Among the reasons why I still see a lot of trucks with drum brakes all-around is they're often pointed out to be less prone to have its friction surfaces in contact with contaminants, which is a common issue on most rural environments. Then it turns out to question the suitability of all-around drum brakes for an economy car, considering not only the manufacturing cost which is still usually lower for a drum brake but also that not every farmer in countries such as mine may afford a medium-duty 4WD truck for instance.

Well the truck brakes are massive, almost filling the offset area of a 20" rim and sticking out from the rim.. You also downshift for hill descent which cars typically don't do as well as being more aware of traffic and driving slower. OTOH, my daughter is complaining to KIA about her rear discs making noise after driving on a dirt road.

I would think that truck discs would be bigger and heavier than the equivalent drum brake

Maybe cheap electric cars will bring back four wheel drums.

Actually expensive electric cars are pushing for high performance drum brakes due to the ease of eliminating brake drag
, there are “supposedly” other benefits as well but maintenance sucks, so there is that.

Either hybrids or full-EVs can be OK with drum brakes as they do regenerative braking.

The VW ID series has drum rear brakes because it is RWD and the electric motor does the vast majority of braking. Drums also make a parking brake easier.

However, plenty of reviews of the car dinged it for having "cheap" drum brakes without looking into the engineering reasons why.

No wonder the drum-in-hat parking brake layout is so common among cars with disc brakes all-around.


Even though some reviewers do have a decent knowledge base, it seems like they try to behave much like they would expect Average Joe to do, including such disregard to a simpler technical approach when something else fancier is available in a comparable product from some other manufacturer.

Recently I had a talk with a friend who worked for a while at the Brazilian branch of Scania, and he is still more favorable to drum brakes on heavy-duty trucks.

The only down side to drum brakes that I know of is dumping the friction heat on twisty roads or long downhills. I know of big rigs water spray cooling on the drums, but that is frowned upon.

The fitment of engine-braking devices and some transmission-mounted braking retarders (either electro-mechanical or hydraulic) may compensate at least a little of the burden which would otherwise be on the brakes.


I have never seen any water spray cooling of the drums on any big rig in my country.

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.

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.

You can drill brake drums as well.

That really helps if you drive through standing water.

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.

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.


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.


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.


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 :turtle:


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

https://content.speedwaymotors.com/P...6fe876dc2.webp

www.speedwaymotors.com/Buick-Style-Finned-Aluminum-Brake-Drum-for-Ford-Spindles

drum brakes are usually lighter than a disc, the caliber and associated brackets needed to mount the caliber. My Tacoma has rear drums.

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.


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.

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!

Speaking of Frozen Rotors:

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Cryogenic tempering FTW. :)

It's often pointed out that service is often an even bigger source of revenue for some dealers than actually selling new cars.


Front discs too. No wonder I have seen so many folks who refuse to adapt disc brakes with off-the-shelf parts from a more recent model-year as an upgrade to some older vehicles still used as a workhorse.

Service is a bigger source of profits for dealers than new car sales but if is important to remember that outside of Tesla - dealerships aren't owned by the manufacturer.

I can flat out say that we do no design cars to fail so dealers can make money on service. The less a customer has to interact with a dealer the better for the manufacturer.

We also make vehicles to be as easy to service as reasonably possible.

Sometimes it feels like that's not the case. (e.g. Right to repair).

Speaking of brakes, I thought that my 8 year old Avalon could use a brake fluid change. Maybe it doesn't, and Toyota doesn't recommend a brake fluid change for the whole life of the vehicle. But seeing how several Prius owners have had their brake actuator go out, which ends up costing well over $1,000 to replace, I thought it might be a good idea to do some preventative maintenance.

But to do it on a hybrid (or maybe on any modern car with ABS) you need the special scan tool from the OEM. In my case, an expensive subscription to Toyota TIS (like $2,000 per year). So I thought I'd just have the dealer do it.

I took it in for an airbag recall and told them to go ahead and change the radiator fluid, the engine oil and the brake fluid. They kept telling me that the transmission also needed it, but I had changed that myself not that long ago. But once all said and done, they had changed everything except the brake fluid. It was nearly 5PM and the dealership is 4 hours from my house. So I gave up and went home.

I still don't have my brake fluid changed and have no hope to ever get it done. Maybe I don't need it. Or maybe in a few months I'll need a $2,000 brake actuator.

That and I can't fix my radio... I've rebuild whole engines before and replaced transmissions and brake systems and entire suspension systems and even have done alignments! But now I can't even change the freaking brake fluid or get my radio to work right!

It's small things like those that are frustrating.

Because Tesla have stores instead of dealerships? The other manufacturers are owned by the UAW.

Makes sense. Well, I often see many people complaining about the higher cost of service at dealers, while independent mechanics provide equivalent service at a more reasonable cost, and eventually get the very same replacement parts cheaper by searching at the supplier's catalog instead of the automaker's.

Right to repair is a tricky subject. There is already a court settlement between independent shops and automakers to provide independent shops access to the diagnostic tools available to dealerships. That happened back in 2014.

The most recent battle has moved beyond just repair and is a fight to gain access to the source code. This is a level of access that even dealerships don't have.

I'm surprised your Avalon doesn't recommend brake fluid changes. My 2005 and 2009 Prius required changes every 2 years - which is pretty standard for any modern car with ABS brakes. The issue is that people that never activate ABS can trap old fluid in the ABS valves and gum them up.

Any independent shop should have a tool capable of activating the ABS system and purging brake fluid on your Toyota. However, if you want to do it the cheap way like me you can simply change the fluid, do a series of hard stops to cycle the ABS and then change the fluid again. Cheaper than a visit to the shop.

When I said automakers try to make vehicles easy to service I was talking about access to parts. I wish more people could see the development process we go through on a new model with service people there giving input from the first digital review.

Looking at the EPA crackdown at some tuning shops due to them tweaking with stock emissions-control systems on Diesel trucks, I guess automakers are even more willing to avoid being held responsible for anything related to that.

Manufacturers aren't worried about getting hit with emission fines for illegal tunes. They are worried about tunes that damage engines within the warranty period and owners trying to commit warranty fraud by claiming the car is stock. As we discussed in another thread manufacturers are in an encryption arms race with turners to lock out illegal tuning and make illegal tuning permanently visible on the ECU. Right to repair advocates are pushing for laws that would require manufacturers to turn over the keys to that encryption.

I'm all for right to repair (RTR). That is to repair your car - to maintain it and keep it running in like new condition. To have access to parts, tools, and repair knowledge. I'm all for allowing work to be done by individuals or independent shops and keep warranty coverage.

I'm not for requiring manufacturers to have to make it easy to illegally modify cars or make warranty fraud easier. It is no surprise that SEMA is actively pushing legislation that would it easier for their members to make illegal tuning products. They know that the vast majority of their business is illegal mods.

I'm also not keen on making the details of OTA updates public as RTR advocates would like. Manufactures are working hard to make ever increasingly connect cars secure from hackers. It seems stupid to just give them all the code.

Interesting. I see that would be a problem. Kind of like giving out the code to unlock cars and reprogram keys and then anyone who wants to become a car thief has suddenly got an easy way to do it.

Or like when people didn't check their tire pressure and then all got SUV's that weigh so much they destroy the tire and lose control when you don't have enough air in one. So then the OEMs have to put tire pressure monitoring systems on their vehicles. Which because of that those of us who like changing their winter and summer tires with their own rims have to either deal with a blinking tire light all winter or pay a shop to either change the rims or the sensor codes.

The point is you can't really trust even your average car owner some times. But on the other hand it's frustrating when you just want to do something that seems like it should be so simple, yet it seems impossible.

I did ask the biggest shop in town if they could change my brake fluid. They said they didn't have the tool to do it. Maybe the next town over, but the road is closed except weekends and it's 3 hours to go around.

That would be called Security Through Obscurity. You can't lock something down if you put an example in each customer's hand.

OTOH the Tesla backend is running the Dojo chip, or will be soon. Reverse engineer that.

archive.org/details/car-hackers-handbook-the

Well, if you look at computers, which cars kind of are, there's a trend to go from "security from obscurity" to full blown locks and encryption.

Take a look at how Microsoft is pushing for all Windows 11 computers to have a Trusted Platform Module (TPM, not to be confused with Tire Pressure Monitor) version 2.0 or newer with secure boot. If they can encrypt hard drives and everything else with secret keys then it becomes a lot harder to hack computers.

The same with cars. If the tele data isn't so already, it will be soon encrypted. I'm sure CAN bus and all that is going to go the same route too if it hasn't. Soon sensors will have encryption chips and send encrypted digital data instead of analog voltage signals like they do now.

I used to live in that world. The Clipper chip and the UEFI bootloader.

I could edit the (Mac) boot blocks with Norton Disk Editor but Symantec never ported it to OSX. Nowadays if I forget the password I'm toast.

What's you favorite flavor of Linux?

Right now I don't have any use for Linux. Very few of the apps I use exist or have suitable alternatives on Linux. This is the same reason I don't consider using MacOS, iOS, iPadOS or a Chromebook. I only use Android for convenience and one other app.

I actually do have one laptop running Linux right now that I picked up for free that I'm thinking of installing Windows XP on it.

Getting back on topic, sort of, the reason I would want to run Windows XP on an old laptop is to run a hacked version of TIS, Toyota's OBD program, so that I can do things to my car like change the TPMS codes or bleed my brakes. I'm still up in the air if I should do that or not...

Yes it is.


That is very odd as ABS is decades old now and the tools are cheap.

Just one vender's offerings: https://www.innova.com/collections/all

So it must have been something else I had asked that they couldn't do. But now I'm not sure what it was or for what vehicle, or if the vehicle was even mine...

Anywho, I went ahead and called them up again today and they said they could do it. I got it scheduled to have the brake fluid flushed on the 27th. I'll let you know how it goes.

I'm not so keen on OTA updates, at all.

Even though nowadays just a few motorcycles and most medium-duty and heavy-duty trucks and bus frames are the last new vehicles featuring all-around drum brakes, and the average Joe perceives it either as inherently inferior or simply "uncool" when it comes to motorcycles as a large front disc (either just bigger than stock or in a different shape such as those wavy discs), I am seeing a reasonable amount of motorcycles originally fitted with a front disc brake converted to drums all around. I guess the ABS mandate for new cars in my country from 2014 on may prevent similar mods to be implemented on cars, yet I'm sure some fleet owners and managers would be more willing to try a similar approach if they could legally do it.

Drum brakes are increasingly rare on medium and heavy duty trucks in the USA today. The Freightliner Cascadia comes standard with disc brakes today - with the option to downgrade to drums.

It still has a greater market share in other countries, and even top-tier makers such as Volvo and Scania have to offer such option in Brazil and parts of Africa for instance. Odd enough, other manufacturers such as Isuzu offer disc brakes on certain models within the lightest and heaviest categories, yet most of the intermediate models retain drums all-around.


Such option remaining available just shows how drums might not be that bad at all, for the right applications, or if the operator or a fleet manager is too concerned about discs bending under harsh operating conditions.