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

[freebeard]

Brakes are so 20th Century. The new room temperature superconductors will someday enable regen (excess dumped as heat) down to 0MPH.

[Piotrsko]

Regen is a function of moving magnetic fields. Would need pretty stiff gearing to get to zero even in a tesla which still uses brakes in the last wee bit of stopping although they could reverse the motor

[j-c-c]

Originally Posted by JSH

I was agreeing with you. JCC is wrong when he says drums went away because of ABS.

Drums went away on the front axle to increase braking power and reduce fading. Drums went away on the rear axle in wealthy countries due to marketing.

Really?
Drums can lock any tire just as well as any disc, ie they have no less advantage in braking power. Actually, drums can lock up better then discs, because they have efficiencies with 'self-energizing" tendencies with dual shoe single cylinder activation. The downside is that that takes time because of mechanical action, and that is the enemy of good ABS solutions. Large Trucks have been on the back side of the road away from drums, mainly because of the disc technology has lagged with the great heat dissipation demands large trucks create. Nascar (heavy, high speeds repeated braking in some cases) had the same issue converting to discs that eventually was resolved. Discs also solve one other crucial performance aspect, that front discs solve, being they do approx 70% of the braking, resistance to water effects under braking, which if present on the rear creates a lot fewer problems than the front, ie they resist lock up, when wet, but are only tasked with 30% of the braking. Brake fade under normal driving conditions is rather rare, very unique and driver avoidable in most cases. ABS is a great safety feature useful at anytime when driving, with every driver.

Your marketing claim for OEM's primary switch to the use of rear discs in everyday cars is without merit, but you are welcome to prove me wrong. I would not argue OEM marketing exploited the rear disc upgrades, and it appears many here drank that Kool aid.

I guess we could also explore the various parking brake solutions of rear drums vs discs, but that maybe just getting into the weeds.

[freebeard]

Regen is a function of moving magnetic fields. Would need pretty stiff gearing to get to zero even in a tesla which still uses brakes in the last wee bit of stopping although they could reverse the motor

Maybe. I'm an engineering drop-out.

If electric motors have 100% torque at 0RPM, wouldn't an electric brake as well? Considering that with brushless motors the rotation of the field is independent of the rotation of the shaft?

FUV have regen, hydraulic brake and an obnoxious electric parking brake.

[Piotrsko]

Yes you can sort of lock a tesla rotor. However when locked, it doesn't generate power because you cannot spin it with the car parts. I wonder if you can slam a tesla into reverse at speed and hit the throttle. Probably breaks stuff or the control system won't allow it. When I get too goofy with my model airplane electrics, it either fries the controller, shorts a field winding or even bends the motor shaft.

Fuv has a smaller motor and less powerful control system as a result. Easier to overpower. And you never approach 100% regen, the last 5mph the motor goes into brake mode.

Electric brakes are an attempt to idiot proof it. Nothing to stop the ranger from rolling downhill with the parking brake off.

[cRiPpLe_rOoStEr]

Even though regenerative braking can be compared to the exhaust-brakes of trucks, they're only supplemental. Sure they can make a brake pad or a brake shoe last much longer, if used properly, but relying exclusively on regen or exhaust-brakes would be too dangerous, and eventually lead to more damage than using those systems correctly.

[j-c-c]

Not sure that analogy is effective here. Regenerative braking has a secondary benefit, charging batteries, an exhaust brake has no secondary benefit.

[JSH]

Originally Posted by j-c-c

Really?
Drums can lock any tire just as well as any disc, ie they have no less advantage in braking power. Actually, drums can lock up better then discs, because they have efficiencies with 'self-energizing" tendencies with dual shoe single cylinder activation. The downside is that that takes time because of mechanical action, and that is the enemy of good ABS solutions. Large Trucks have been on the back side of the road away from drums, mainly because of the disc technology has lagged with the great heat dissipation demands large trucks create. Nascar (heavy, high speeds repeated braking in some cases) had the same issue converting to discs that eventually was resolved. Discs also solve one other crucial performance aspect, that front discs solve, being they do approx 70% of the braking, resistance to water effects under braking, which if present on the rear creates a lot fewer problems than the front, ie they resist lock up, when wet, but are only tasked with 30% of the braking. Brake fade under normal driving conditions is rather rare, very unique and driver avoidable in most cases. ABS is a great safety feature useful at anytime when driving, with every driver.

Your marketing claim for OEM's primary switch to the use of rear discs in everyday cars is without merit, but you are welcome to prove me wrong. I would not argue OEM marketing exploited the rear disc upgrades, and it appears many here drank that Kool aid.

I guess we could also explore the various parking brake solutions of rear drums vs discs, but that maybe just getting into the weeds.

Yes, a drum can stop as fast as a disk - once. Then they start overheating and fading. Overheating a set of brakes on even a modern vehicle with discs is not that uncommon. Maybe you don't see in in Florida were passes are 3 feet above sea level but in mountainous areas where crossing a pass is thousands of feet up and then down people ride their brakes and overheat them all the time. The smell of cooked brakes is an every trip occurrence when I head across the Cascades and I've actually stopped and used a fire extinguisher to put out a fire where someone is an old 80's Chevy Malibu had ridden their brakes for so long that the brakes caught on fire.

Cars got front brakes first because the front axle does the bulk of braking so that is where strong and fade resistant brakes are needed most. Rear brakes rarely do enough braking to require disks outside of performance cars. Drums are also cheaper than discs so budget cars generally got drums. Combine these together and cars that don't need discs in the rear got them because the public (and automotive editors) complained about perfectly adequate drum brakes.

A recent example of this is the VW ID.4 that has rear drums. This is a perfectly logical engineering solution because drums are cheap and not only does the rear axle not do much braking but the ID.4 is RWD so 99% of rear braking is done with regen. However pretty much every first review of the ID.4 pointed out the rear drums and said something to the effect of "WOW VW is really be cheap - can you believe they used drum brakes on a $45K vehicle!)

Heavy duty trucks got discs to increase stopping power and reduce fade. How do I know? I work for a manufacturer of HD trucks and when we made discs standard I walked over to the brake group and asked why and that is what they said. I also asked why we still offer the option of drums and I was told it was because some fleet service managers don't like discs because they resist fade and therefore drivers use the brakes more - which means they go through pads quicker and trucks spend more time in the shop. I was also told that people that use their trucks off-highway for things like logging prefer drums.

Originally Posted by freebeard

FUV have regen, hydraulic brake and an obnoxious electric parking brake.

Electric parking brakes have steadily replaced manual cable activated brakes because they are MUCH easier to package. They can also be automatically applied when the car is shifted into park.

[freebeard]

Electric parking brakes have steadily replaced manual cable activated brakes because they are MUCH easier to package

Okay, but the obnoxious part is that it takes1-2 seconds and makes a whiring sound. Some stepper motor with a dumb-*ss controller?

Also, the regen down to 0MPH were posited on the advent of room temp superconductors.

[JSH]

Originally Posted by freebeard

Okay, but the obnoxious part is that it takes1-2 seconds and makes a whiring sound. Some stepper motor with a dumb-*ss controller?

Why does that matter? Push the button and walk away. Yes, the electric motor makes noise - it does in cars too.

Mechanical parking brakes make noise too - just a different noise. Mine makes a click - click - click as the lever passes each ratchet and then a loud pop when I release the parking brake and the pedal pops back up.