Speak EV - Electric Car Forums banner

61 - 80 of 85 Posts

Registered
Joined
108 Posts
I personally think that it's ridiculous to fit drum brakes on a 40k car.
I find it even more ridiculous that they're trying to spin a cost-saving measure as an improvement.

The brakes tend to corrode on Tesla's because of poor engineering and using cheap parts on an expensive car, not because they are not used.
EV's from legacy manufacturers are not reporting such problems.
That's why while you enjoy your gorgeous big tablet screen in the cabin of your Model S, your brakes, an essential safety feature, will be delaminating:



So do you have full regen on a ID4 with 100% SOC?
I doubt it.
Also, remember that regen is meant to slow down a car over a long distance, while brakes are meant to slow down the car in as little a distance as possible.

The rear brakes may contribute less to braking, but they contribute nonetheless and that's not irrelevant on a car that weighs close to 3 tons with a full load.

Also, drum brakes on the rear axle tend to give the car this tendency for the car's front to lean down when braking, a generally uncomfortable feeling.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


Another note of the bottom, it's ridiculous that they didn't even bother to apply at least a coat of paint to that huge galvanised steel plate below the car.
For something static and meant to be cheap, that would be ok, but this is a car and little jumping debris will scratch the galvanisation and with the salt eating away at it, it will be happy hour for penetrating rust and I don't know what that plate is welded to (battery pack? I see welding points at the front) but it can quickly become an expensive mess.



If you look below most cars, the chassis has a layer of sealant applied to it to prevent rusting.
And as you can see from the below video of a rusting VW, even the sealant can not entirely prevent rusting so imagine what bare galvanised steel is going to look like after 5 years of salty roads...

 

Registered
Joined
4,602 Posts
I personally think that it's ridiculous to fit drum brakes on a 40k car.
I find it even more ridiculous that they're trying to spin a cost-saving measure as an improvement.

The brakes tend to corrode on Tesla's because of poor engineering and using cheap parts on an expensive car, not because they are not used.
EV's from legacy manufacturers are not reporting such problems.
That's why while you enjoy your gorgeous big tablet screen in the cabin of your Model S, your brakes, an essential safety feature, will be delaminating:



So do you have full regen on a ID4 with 100% SOC?
I doubt it.
Also, remember that regen is meant to slow down a car over a long distance, while brakes are meant to slow down the car in as little a distance as possible.

The rear brakes may contribute less to braking, but they contribute nonetheless and that's not irrelevant on a car that weighs close to 3 tons with a full load.

Also, drum brakes on the rear axle tend to give the car this tendency for the car's front to lean down when braking, a generally uncomfortable feeling.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


Another note of the bottom, it's ridiculous that they didn't even bother to apply at least a coat of paint to that huge galvanised steel plate below the car.
For something static and meant to be cheap, that would be ok, but this is a car and little jumping debris will scratch the galvanisation and with the salt eating away at it, it will be happy hour for penetrating rust and I don't know what that plate is welded to (battery pack? I see welding points at the front) but it can quickly become an expensive mess.



If you look below most cars, the chassis has a layer of sealant applied to it to prevent rusting.
And as you can see from the below video of a rusting VW, even the sealant can not entirely prevent rusting so imagine what bare galvanised steel is going to look like after 5 years of salty roads...

Sorry, what was your point馃槣
 

Registered
Renault Zoe 50
Joined
19,856 Posts
The brakes tend to corrode on Tesla's because of poor engineering and using cheap parts on an expensive car,
You know Tesla get their brakes from Brembo?

But please tell me more about all the things you know about Teslas.
 

Registered
Joined
108 Posts
The difference is the resister wouldn鈥檛 wear out like a brake pad. You also reduce the parts count and weight.

Cooling of the resister would just be a fan, or ducted air.
Resistors wear out too due to thermal stress / fatigue.
Ducted air would not cool down a resistor after braking because the car would probably stopped.
Fans would consume energy,
You would need big resistors and lots of fans to achieve the same energy absorption as a block of metal that is a brake disc.
If you go for something like that, you might as well power a flywheel and offset the movement. The flywheel can then charge the battery in its own time.


By the way, given that you're an aircraft engineer, you would be interested to know that Airbus patented something where the braking energy absorption was offset from the wheels. They were not specific as to what the heat absorption device was made of though, except that it was a phase change material.

the electric controller of said at least one electric motor is connected to an energy absorber making it possible to absorb the electric energy produced by said at least one electric motor when the latter is operating in generator mode.

So that could be another option.


Just realise that braking takes up a lot of energy in a very short timespan, and there is a reason why steel and carbon brakes have been used for so long.
They are simple and relatively low maintenance.
 

Registered
Joined
108 Posts
You know Tesla get their brakes from Brembo?

But please tell me more about all the things you know about Teslas.
I don't know who makes those brake pads and I couldn't care less other than for the fact that they are rubbish.
That video says enough doesn't it? Delaminating brake pads on a max. 5 year old Tesla.
If Brembo makes them, then shame on them.
Or is it one of those things that a generic supplier makes for them and they put their tag on it?
That's a recent facelift Model S, so it should still be the originals.

This is what Elon Musk said about it:
Brake pads on a Tesla literally never need to be replaced for lifetime of the car.

I give credit to Elon Musk as a salesman, but we wouldn't be talking about this if his cars were as good as his mouth.

If you want to know more about the brake issues on the Model S, you can have a read here:
 

Registered
Joined
42 Posts
I personally think that it's ridiculous to fit drum brakes on a 40k car.
I find it even more ridiculous that they're trying to spin a cost-saving measure as an improvement.
not sure I understand your reasoning... as mentioned above by someone who knows a little more about the technology than you or I, A brake helps stop the car but in an ICE car, converts much of the kenetic energy into heat.
In an EV, we have motors, so we want to convert the kenetic energy into power to put back into the battery, so we want to use the brakes less and only where the motors need extra help to stop faster.

Next there is this thing about balance... we dont need to put all the stopping force in the rear wheels we want to bias towards the front... If you have ridden a bicycle and hit the rear brake harder than the front you know you skid, so you put a fraction more force on the front.

So drum brakes in the back of the car to accompany the motors makes a lot of design and mechanical sense to me.

What's your point to say it is rediculous... is it just familiarity with ICEs and disks all around? So drum brakes in the back feels like a thing from the early 90's?
Well dont forget in the 90's when we had front disks and rear drums the drums did 100% of the work in the rear, now they are there to support the motors which are harvesting most of the energy... you have two types of brakes operating in the back of the car sharing the work!
 

Registered
VW ID.3 Family
Joined
235 Posts
This is a rear disc (MOT failure) from a my OH's 9 year old 50k Audi A1 - lost almost no thickness, but rusted to death.

Rear discs have almost no value in a small, lightweight hatchback that doesn't get driven hard.

Original pads were badly grooved, but still plenty of base material left as well.

143114
 

Registered
Joined
4,602 Posts
This is a rear disc (MOT failure) from a my OH's 9 year old 50k Audi A1 - lost almost no thickness, but rusted to death.

Rear discs have almost no value in a small, lightweight hatchback that doesn't get driven hard.

Original pads were badly grooved, but still plenty of base material left as well.

View attachment 143114
There is evidence on that disc of misalignment between pad and disc, caused by corrosion at the back of the pads, the caliper fists, the piston, the caliper mounts etc.

VW and Continental have done a smart but logical thing in fitting their completely redesigned drum brake to the rears: evidence of good design and moving away from ICE truisms.
 

Registered
Kia e-Niro 4 MY20
Joined
650 Posts
I personally think that it's ridiculous to fit drum brakes on a 40k car.
I find it even more ridiculous that they're trying to spin a cost-saving measure as an improvement.

The brakes tend to corrode on Tesla's because of poor engineering and using cheap parts on an expensive car, not because they are not used.
EV's from legacy manufacturers are not reporting such problems.
That's why while you enjoy your gorgeous big tablet screen in the cabin of your Model S, your brakes, an essential safety feature, will be delaminating:



So do you have full regen on a ID4 with 100% SOC?
I doubt it.
Also, remember that regen is meant to slow down a car over a long distance, while brakes are meant to slow down the car in as little a distance as possible.

The rear brakes may contribute less to braking, but they contribute nonetheless and that's not irrelevant on a car that weighs close to 3 tons with a full load.

Also, drum brakes on the rear axle tend to give the car this tendency for the car's front to lean down when braking, a generally uncomfortable feeling.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


Another note of the bottom, it's ridiculous that they didn't even bother to apply at least a coat of paint to that huge galvanised steel plate below the car.
For something static and meant to be cheap, that would be ok, but this is a car and little jumping debris will scratch the galvanisation and with the salt eating away at it, it will be happy hour for penetrating rust and I don't know what that plate is welded to (battery pack? I see welding points at the front) but it can quickly become an expensive mess.



If you look below most cars, the chassis has a layer of sealant applied to it to prevent rusting.
And as you can see from the below video of a rusting VW, even the sealant can not entirely prevent rusting so imagine what bare galvanised steel is going to look like after 5 years of salty roads...

Rear discs are a me too thing. They鈥檙e not better than drums in most practical circumstances. Disc brakes don鈥檛 necessarily offer better stopping power. As mentioned they鈥檙e primarily about repeatability and are better in circumstances where the brakes are used a lot and will build up a lot of heat. Many years ago, in my parent鈥檚 crap car of the time, there was a close call when the brakes started to fade badly going down Blue Bank near Whitby. Scary times. This is where vented discs are better, brakes being needed to control speed on steep hills. Having just driven my e-Niro around some of North Yorkshire鈥檚 particularly steep bits, the regen entirely takes care of controlling speed. The brakes are barely used. Rear drums make perfect sense.
 

Registered
Joined
108 Posts
not sure I understand your reasoning... as mentioned above by someone who knows a little more about the technology than you or I, A brake helps stop the car but in an ICE car, converts much of the kenetic energy into heat.
In an EV, we have motors, so we want to convert the kenetic energy into power to put back into the battery, so we want to use the brakes less and only where the motors need extra help to stop faster.

Next there is this thing about balance... we dont need to put all the stopping force in the rear wheels we want to bias towards the front... If you have ridden a bicycle and hit the rear brake harder than the front you know you skid, so you put a fraction more force on the front.

So drum brakes in the back of the car to accompany the motors makes a lot of design and mechanical sense to me.

What's your point to say it is rediculous... is it just familiarity with ICEs and disks all around? So drum brakes in the back feels like a thing from the early 90's?
Well dont forget in the 90's when we had front disks and rear drums the drums did 100% of the work in the rear, now they are there to support the motors which are harvesting most of the energy... you have two types of brakes operating in the back of the car sharing the work!
First of all, what you and Mr Bjorn Tesla are forgetting is that ICE cars also have engine braking.
I use it so much that my 2003 Corolla is still on its first set of discs in the front at 200k miles. The clutch is also the factory one despite all that engine braking, now that is quality.
Depending on the gear the car is in, it may not be as powerful as regen on the newer EV鈥檚 but it actually can do its job, also during emergency braking.
Typically, during hard braking, if you don鈥檛 have time to unclutch, your engine will detonate and help with deceleration.

Second of all, calling drum brakes 鈥渢echnology鈥 is a stretch too far imo.
Also saying that I don鈥檛 know as much as someone else is a bit ridiculous for simple pieces of hardware as car brakes.
What is there to know?
And I wouldn鈥檛 mention this normally but I disassembled and reassembled several Meggitt carbon brake packs as introductory training during my aerospace years and even those are not worthy of calling technology IMO.
You are judging people without knowing who they are.

Third, drum brakes have always been chosen to cut costs on a lighter, economical car.
But they are expensive and less easy to maintain, so your servicing bill will go up.
The drum brakes typically need to be lubricated and adjusted at certain intervals.

Fourth, max regen does not engage instantly. The motor management computer will typically lag a few moments before engaging generator mode. This is usually built into the software to preserve the longevity of the motor but also for reasons of comfort. You don鈥檛 want it to start braking the very moment that you slightly relieve the pressure on the throttle pedal.
This greatly reduces the impact of regen during emergency stopping.

Fifth, regen is not reverse as some seem to think it is. It鈥檚 just your motor switching over to generator mode. So at best, it can only regen at the max power output of your motor minus losses, but this is actually also limited by the rate at which the energy can be converted and absorbed by the transformer rectifier- battery combo.
Brakes can stop your car in much shorter a distance than your motors take to accelerate it to a certain speed.

I see brakes primarily as a device intended to save my life when ouch comes to shove, not as a speed adjusting device.
The reason why EV brakes are oversized for their usage is because when full braking power is needed, they are there to stop the heavier EV鈥檚.
So no matter how much regen you have available, I wouldn鈥檛 want to rely on drum brakes to stop a 2.7 ton car from 60 to zero in 100 meters.

Let鈥檚 see some brake distance tests.
Without doubt, they will underperform, especially after driving a while on roads with lots of tight curves and steep downhill stretches.

Besides the cost- advantage for VW, what advantage is there for the driver?
As said earlier, corrosion is not a matter of not using the brakes as much on EV鈥檚 it鈥檚 a matter of the quality of the brakes used by the OEM. Cr*p brakes corrode on ICE鈥檚 too.

Using drum brakes on a heavy car is just a bad idea.
Saving pennies on a 40k car is just cheap.

If VW went cheap on the brakes, I wonder what else they went cheap on.
 

Premium Member
VW ID.3 Worst Edition & Tesla M3 LR
Joined
5,919 Posts
Discussion Starter #71
Besides the cost- advantage for VW, what advantage is there for the driver?
As said earlier, corrosion is not a matter of not using the brakes as much on EV鈥檚 it鈥檚 a matter of the quality of the brakes used by the OEM. Cr*p brakes corrode on ICE鈥檚 too.
You know they鈥檙e cheaper than a caliper and a disc how?

Using drum brakes on a heavy car is just a bad idea.
Saving pennies on a 40k car is just cheap.
Yet they seem to be a good idea on many trucks? Again, you鈥檙e assuming they鈥檙e cheaper than just throwing on a set of rear discs and calipers from another VW model.

Your thinking seems to be stuck in the past, you ignore all the engineering and practical reasons why they chose this for the ID.3 and 4, and instead fixate on the 鈥榙rum brakes on a 拢40k car, lolz鈥 trope.

If VW went cheap on the brakes, I wonder what else they went cheap on
I don鈥檛 know, but they found the money to water cool and heat the battery.
 

Registered
Joined
4,602 Posts
First of all, what you and Mr Bjorn Tesla are forgetting is that ICE cars also have engine braking.
I use it so much that my 2003 Corolla is still on its first set of discs in the front at 200k miles. The clutch is also the factory one despite all that engine braking, now that is quality.
Depending on the gear the car is in, it may not be as powerful as regen on the newer EV鈥檚 but it actually can do its job, also during emergency braking.
Typically, during hard braking, if you don鈥檛 have time to unclutch, your engine will detonate and help with deceleration.

Second of all, calling drum brakes 鈥渢echnology鈥 is a stretch too far imo.
Also saying that I don鈥檛 know as much as someone else is a bit ridiculous for simple pieces of hardware as car brakes.
What is there to know?
And I wouldn鈥檛 mention this normally but I disassembled and reassembled several Meggitt carbon brake packs as introductory training during my aerospace years and even those are not worthy of calling technology IMO.
You are judging people without knowing who they are.

Third, drum brakes have always been chosen to cut costs on a lighter, economical car.
But they are expensive and less easy to maintain, so your servicing bill will go up.
The drum brakes typically need to be lubricated and adjusted at certain intervals.

Fourth, max regen does not engage instantly. The motor management computer will typically lag a few moments before engaging generator mode. This is usually built into the software to preserve the longevity of the motor but also for reasons of comfort. You don鈥檛 want it to start braking the very moment that you slightly relieve the pressure on the throttle pedal.
This greatly reduces the impact of regen during emergency stopping.

Fifth, regen is not reverse as some seem to think it is. It鈥檚 just your motor switching over to generator mode. So at best, it can only regen at the max power output of your motor minus losses, but this is actually also limited by the rate at which the energy can be converted and absorbed by the transformer rectifier- battery combo.
Brakes can stop your car in much shorter a distance than your motors take to accelerate it to a certain speed.

I see brakes primarily as a device intended to save my life when ouch comes to shove, not as a speed adjusting device.
The reason why EV brakes are oversized for their usage is because when full braking power is needed, they are there to stop the heavier EV鈥檚.
So no matter how much regen you have available, I wouldn鈥檛 want to rely on drum brakes to stop a 2.7 ton car from 60 to zero in 100 meters.

Let鈥檚 see some brake distance tests.
Without doubt, they will underperform, especially after driving a while on roads with lots of tight curves and steep downhill stretches.

Besides the cost- advantage for VW, what advantage is there for the driver?
As said earlier, corrosion is not a matter of not using the brakes as much on EV鈥檚 it鈥檚 a matter of the quality of the brakes used by the OEM. Cr*p brakes corrode on ICE鈥檚 too.

Using drum brakes on a heavy car is just a bad idea.
Saving pennies on a 40k car is just cheap.

If VW went cheap on the brakes, I wonder what else they went cheap on.
Look mate, I'm willing to bet that pretty sure all BEV manufacturers of ordinary cars (out with a full electric Ferrari) will fit drum brakes similar to the Continental non servo design. Thermal management will no doubt be part of the design just like dynamic stability. For one off emergency stopping scenarios, only needing to absorb kinetic energy, not long duration gravitational energy absorption, rear drums are more than suitable.
 

Registered
Joined
4,602 Posts
You know they鈥檙e cheaper than a caliper and a disc how?



Yet they seem to be a good idea on many trucks? Again, you鈥檙e assuming they鈥檙e cheaper than just throwing on a set of rear discs and calipers from another VW model.

Your thinking seems to be stuck in the past, you ignore all the engineering and practical reasons why they chose this for the ID.3 and 4, and instead fixate on the 鈥榙rum brakes on a 拢40k car, lolz鈥 trope.



I don鈥檛 know, but they found the money to water cool and heat the battery.
Great post. VW have started with a clean sheet and the braking system is a result of intelligent choices.
 

Registered
Joined
2,026 Posts
Third, drum brakes have always been chosen to cut costs on a lighter, economical car.
But they are expensive and less easy to maintain, so your servicing bill will go up.
The drum brakes typically need to be lubricated and adjusted at certain intervals.
No. Pads and calipers should also be taken apart, cleaned, and lubricated regularly but almost nowhere does this due to time/cost. Easier to get the customer to stump up 拢300 for a new caliper, or 拢200 for pads/discs every few years.

Only issues I had with rear drums was brake cable replacement (probably irrelevant to type of braking system), and a slave cylinder failure (in a 25 year old Triumph).

I have replaced dozens of pads/discs, and a few calipers in my time.
 

Registered
Joined
42 Posts
Im laughing at the debate here... half people are saying regen and drums are a good move, and half are saying expect disks.
Each have some valid points but the fact that multiple EVs use drums indicate the designers have a perspective.

Now for those who dont think the regen function reacts slowly or cant slow the car quickly... watch the carwow video on the Audi etron GT... there is a piece there where he comments on how effective the stopping is on the regen. (cant be bothered to watch it again and tell you where) but it highlights that the main stopping is from the regen function.

However this article explains the real reason you then need a brake... basically you need it to come to a complete stop and to hold the car stationary... in other words, any brake will do the job you dont need a disk brake.

.
 

Registered
Joined
4,602 Posts
Im laughing at the debate here... half people are saying regen and drums are a good move, and half are saying expect disks.
Each have some valid points but the fact that multiple EVs use drums indicate the designers have a perspective.

Now for those who dont think the regen function reacts slowly or cant slow the car quickly... watch the carwow video on the Audi etron GT... there is a piece there where he comments on how effective the stopping is on the regen. (cant be bothered to watch it again and tell you where) but it highlights that the main stopping is from the regen function.

However this article explains the real reason you then need a brake... basically you need it to come to a complete stop and to hold the car stationary... in other words, any brake will do the job you dont need a disk brake.

.
Hey we could start a debate on VWs underbody aero design.
Starter, its very poor and they cheaped out: should have applied proper sideskirts and ground force / road clearance control integrated with LIDAR.. Considering the cost of the car it is scandalous!
 

Registered
Joined
42 Posts
Considering the cost of the car it is scandalous!
Then dont buy one! It really is that simple.

and there is no point in moaning here about it because VW dont read this forum... write to VW's exec team, their emails are easy to google. Im sure they will appreaciate your feedback.
 

Registered
Joined
108 Posts
When I have time, I will get a VW dealer to lend me an ID4 and I'll do some braking tests with it.
If after the tests I feel that it's fine, I will post here that it's fine and redact my current pointof view.

I don't know of other EV manufacturers using drum brakes.

Drum brakes are cheaper to manufacture.
Not by much, but they are.
Maybe 100 EUR per car?
That's why it's a ridiculous saving on this kind of expensive car.

99% of the time this will be just fine, actually.
The problem is that 1% when you need all the braking power you can use.
Losing 20 meters of braking distance could be the difference between life and death.
Not a compromise that you should be accepting in this budget class.
 

Registered
Joined
4,602 Posts
Then dont buy one! It really is that simple.

and there is no point in moaning here about it because VW dont read this forum... write to VW's exec team, their emails are easy to google. Im sure they will appreaciate your feedback.
O dear, my attempt at irony failed馃ぃ
 

Registered
Joined
108 Posts
Look mate, I'm willing to bet that pretty sure all BEV manufacturers of ordinary cars (out with a full electric Ferrari) will fit drum brakes similar to the Continental non servo design. Thermal management will no doubt be part of the design just like dynamic stability. For one off emergency stopping scenarios, only needing to absorb kinetic energy, not long duration gravitational energy absorption, rear drums are more than suitable.
I'm willing to bet that VW is going to switch the drums to disc brakes at some point.
Germans will be very critical and horrified by this.

And nobody finds it odd that VW didn't bother to put a coat of paint or sealant on that galvanised steel underbody skid plate?
 
61 - 80 of 85 Posts
Top