VW says that the rear brakes are used so rarely (remember, the motor on the rear axle does all the regenerative braking before the physical brake needs to kick in, first in front and if necessary in the back) that the disk would corrode. In practice, I think you’d experience “sticky” braking. So VW chose Continental’s new low maintenance drum brake which comes with a 150,000 km service interval. Smart move I’d say.

 

VW says that the rear brakes are used so rarely (remember, the motor on the rear axle does all the regenerative braking before the physical brake needs to kick in, first in front and if necessary in the back) that the disk would corrode. In practice, I think you’d experience “sticky” braking. So VW chose Continental’s new low maintenance drum brake which comes with a 150,000 km service interval. Smart move I’d say.

Ok, this seems to make sense, but issues with panic braking comes to mind though. I guess we will see how it plays out in time.

 

They said that disk brakes by their nature constantly have a small amount of drag that drum brakes do not. Also the drum brake is necessary for making the emergency brake possible.

Perhaps drum brakes save some weight saving? Perhaps drum brakes save them some $$$.

 

VW also claims drum brakes are less draggy than disk brakes, especially over time. One of the video reviews of driving the ID.4 showed a panic stop and driver was surprised on how quick the car stopped. He didn't do formal stopping distance test, it was just a seat of the pants stand on the brake pedal test.

 

The disadvantage of drum brakes would be apparent if the car was tested with repeated heavy braking over a short period of time. A single panic application is a good enough test of the car for most drivers‘ needs, though. This car isn’t designed for the track.

 

I remember the transition from drums to discs. One of the advantages of discs is the superior cooling. Very important on the track, but also in real life. If one has to ride the brakes going down a steep incline, drum brakes will overheat and this was one of the reasons that in the olden days there would be signs on a hill to shift to a lower gear so that engine compression would assist in speed management. I can tell you that the regenerative braking on an EV, including PHEV's, makes braking totally unnecessary and is the EV equivalent of "compression braking". Weight and simplicity is also aided with drum brakes. Many cars have a small "hat" attached to the rear axle for a small drum brake for the parking brake. This adds complexity and un-sprung weight to the rear wheel assembly. While I was initially put off by the VW decision, I now applaud it for out of the box thinking. We'll probably see this having wider application for non-performance EV's.

 

I agree with @ted99 and @Huey52 , the rear drum brake is vey likely a wise decision on VW’s part, and not your 1970 tech either.

 

One more thought; many vehicles with disc brakes have a small drum brake within as the emergency brake. If it's good enough for that condition ....
But for me the biggest EV-plus is that there's no drag in drums as there often is with disc brakes (whether by cleaning/cornering assist design or just natural occurrence). We want motor regeneration when slowing down but certainly not any other resistance to miles-per-charge.

 

An article I read a few weeks (months?) back pointed out that disc brakes need to be used somewhat frequently or the discs begin to oxide & lose effectiveness, and the engineers felt that, with this design (regenerative braking, one pedal driving, whatever you want to call it), the rear brakes would rarely be used. So, in that author's mind, drum brakes were an upgrade as they would last longer with similar stopping power. Sorry I couldn't find a link to the article, but I did look thru my history - there's just so many ID.4 articles over the last few months.

 

Yup, I have read the same thing but it doesn't sound like it was written by the same author. I have been working on vehicles for 45 years, it is VERY rare that I find a disc brake that isn't rubbing causing some drag. In this application, a quality drum brake setup is superior to a disc brake for several reasons. Newer doesn't mean better, just look at the AC and volume controls on the ID.4. Most of the time they work the first time, but all too often they don't work. At least according to the reviews I have been watching/reading on the ID.3. I have seen the same complaints on the same setup on the latest Golf. I am not convinced a software change will fix this issue. Every review has noted/complained about the lack of a volume knob you can turn. Just because you can, doesn't mean you should.
In this application, drum brakes are a better choice than disc brakes.

 

I was really looking hard at the ID 4 until I found out it had rear drum brakes! The aesthetics alone makes me want disc brakes in the rear! It seems like Volkswagen believes that we really don't need rear brakes because the motor helps stop the car! Don't believe the hype disc brake system in the rear is more expensive than a drum brake system because most disc brake systems incorporate a drum inside of the rotor anyway for the parking brake! I love the truck I just hope they change that on the all-wheel drive version! Volkswagen if you're reading this I WANT MY FOUR CALIPERS!

I remember the transition from drums to discs. One of the advantages of discs is the superior cooling. Very important on the track, but also in real life. If one has to ride the brakes going down a steep incline, drum brakes will overheat and this was one of the reasons that in the olden days there would be signs on a hill to shift to a lower gear so that engine compression would assist in speed management. I can tell you that the regenerative braking on an EV, including PHEV's, makes braking totally unnecessary and is the EV equivalent of "compression braking". Weight and simplicity is also aided with drum brakes. Many cars have a small "hat" attached to the rear axle for a small drum brake for the parking brake. This adds complexity and un-sprung weight to the rear wheel assembly. While I was initially put off by the VW decision, I now applaud it for out of the box thinking. We'll probably see this having wider application for non-performance EV's.

There is no advantage to having drum brakes as opposed to rear brakes on a car these days, with one exception it is cheaper to produce a car with disc brakes in the front and drum brakes in the rear then it is to have disc brakes all the way around and a car that looks that nice should have disc brakes in the rear just for aesthetics alone! $50,000 + for an all-wheel drive SUV with a drum brake system in the rear not a good sale, especially for someone who knows better! VOLKSWAGEN IS JUST SAVING ON COST!

 

It’s unfortunate that you’ve totally missed the logical engineering rationale for the rear drum brakes. 🤦🏼‍♂️

I was really looking hard at the ID 4 until I found out it had rear drum brakes! The aesthetics alone makes me want disc brakes in the rear! It seems like Volkswagen believes that we really don't need rear brakes because the motor helps stop the car! Don't believe the hype disc brake system in the rear is more expensive than a drum brake system because most disc brake systems incorporate a drum inside of the rotor anyway for the parking brake! I love the truck I just hope they change that on the all-wheel drive version! Volkswagen if you're reading this I WANT MY FOUR CALIPERS!

There is no advantage to having drum brakes as opposed to rear brakes on a car these days, with one exception it is cheaper to produce a car with disc brakes in the front and drum brakes in the rear then it is to have disc brakes all the way around and a car that looks that nice should have disc brakes in the rear just for aesthetics alone! $50,000 + for an all-wheel drive SUV with a drum brake system in the rear not a good sale, especially for someone who knows better! VOLKSWAGEN IS JUST SAVING ON COST!

 

This is not here for savings and making cheaper EV....it is there for having longer life cycle vs disc brakes....less weight ..... integration of one system for transmission park ( in regular transmission there is another locking mechanism) and etc... and in emergency braking rear axles contribute less than 30% in stopping the car. So whoever thinks that disc brakes are better in the rear vs drum type are misinformed.
Now on top of this you have to account that EV has another advantage vs ICE ....it will assist with regen and drum brakes in emergency stopping.
And for people that think multiple emergency stops will overheat rear drums...you are wrong...it will cook front discs way before it will show any signs of overheating on drums with regen assist.

 

You've already answered my question with your answer it cost less to have drum brakes on the rear! Rear disc with the parking brake inside the rotor will sit there under proper use at least 200,000 MI! If you can make that drum break look like a disc brake on a nice looking truck like that I will by your argument! Nice looking Wheels and a ugly drum in the rear, Volkswagen may have missed its mark! I'm also willing to bet that underneath all that fancy interior the electronics in that in that car leaves a lot to be desired problems waiting to happen! Cheaping out on rear brakes give me pause!

 

Seriously, there's no point arguing about this here. VW made design choices based on many factors one of which was cost. Not just manufacturing cost but long term maintenance/replacement cost to owners.

You are free to disagree and not buy one, leaving one more ID.4 available for people who want one.

 

Seriously, there's no point arguing about this here. VW made design choices based on many factors one of which was cost. Not just manufacturing cost but long term maintenance/replacement cost to owners.

You are free to disagree and not buy one, leaving one more ID.4 available for people who want one.

Not arguing at all! Just letting prospective buyers know that changing brake pads on a disc is cheaper than changing drum brakes, and to keep them safe by letting them know if they ride those drum brakes on that new car that will also take away the main breaking from the rear disc brakes have drums separated from the main breaking! Can't depend on regenerative braking on a rear wheel drive car as much as you can from a front-wheel drive car! For safety sake you need that extra level of protection that a rear disc drum system provides!

 

I'm not here to argue I'm just here because I thought this was an informative forum! I am only here to inform people of potential problems that may arise with drum brakes in the rear! An electric vehicle with rear wheel drive only just in my opinion can be problematic for many drivers because it has drum brakes in the rear and the regenerative braking in a rear drive only EV is not going to stop that well .If it were front-wheel drive first it would be a different story it would have stronger regenerative braking.Another thing if that EV doesn't have automatic parking brake release when you engage the drive mode, you run the risk of burning out your rear brakes prematurely and since that's the only mechanical braking system you have back there you would have lost at least 20 to 30% of your braking capacity because you have no primary brake system after that! I'm not asking anyone to take my word for it just research it and use your common sense, three ways to stop is always better than two (regenerative, parking, primary breaking!)

 

Greenlineguy, I'm thinking from Post #24 that you have never driven an ID.4? Wait until you find out that there is no parking brake as you're describing it and that those dumb engineers at VW pretty much sealed those drum brakes.

 

Yes I have driven the ID 4 pro s rear wheel drive! I like the vehicle but it didn't stop as well as I thought it should. I hope they put rear disc on the back of the all-wheel drive version! Also I was comparing the breaking with a rear wheel drive Tesla model 3 and a Chevrolet Bolt. Both stopped better in my opinion!

 

I am trying to understand your logic and am wondering if you think that the regenerative braking actually uses the drum mechanism to work? it does not. When the ID.4 engages regenerative braking it reverses the polarity in the electric traction motor to apply an opposite/resistive torque to the rear wheels. The drum brakes do nothing under regen, just like rear discs on every EV that has them. The rear brakes on any ICE car really don't do much either and the actual braking force is on the front wheels and not the rear (usually in the range of a 90/10 or 80/20 split) unless there is panic braking. The reason behind drums is that with the regen braking they would only really be used in those panic situations....the same as if they were discs....in any EV the rears really never do anything

there is an automatic parking brake release when you engage the traction motor so there is no way to forget and leave it on, it releases it for you. And there are 3 ways to stop: regen, friction brake, and parking brake.

if you are concerned with the looks of drums in the rear you could always paint them to look like a disc.

 

Let me clear that up for you the mechanical braking system front disc rear disc or drum has nothing to do with the regenerative braking of the motor, it is an independent system! I am very much aware that electric vehicles use the electric motor for some of the breaking! Disc brakes in the rear of a car helps stop the car better than drum will ever do. Electric vehicles with regenerative braking for the most part will see their brake system front disc rear disc system or front disc rear drum system both will last over 100,000 MI if used properly with the regenerative braking . I was saying exactly what you said in your writing if you have to come to an emergency stop you want a rear brake to be a disc! The rear brake system on the on the Volkswagen ID4 would be cheaper to replace in the event of a catastrophic rear brake system failure then a rear disc system, but outside of that happening rear disc brakes pads are easier to replace than drums!

 

I love my ID.4 and trust VW knows what they are doing and that if i ever need to slam on the brakes, the car will stop. VW is not a company to just design something to save money unless the savings make sense for the consumer’s pocket and it doesn’t compromise safety. I haven’t seen a good real argument as to why the rears should be disc brakes, so I’m done reading this thread. Here’s a good article to learn more:

https://www.google.com/amp/s/www.engadget.com/amp/how-the-rising-popularity-of-e-vs-could-lead-to-a-resurgence-of-drum-brakes-170000388.html

 

I'm glad you enjoy your ID4! I'm just looking at the breaking system from a different perspective, because of the fact that electric vehicles have regenerative braking some manufacturers are looking to cut costs anywhere they can! If you're happy with a little less breaking power it's fine with me, but I've been working on cars for over 45 years I know the difference between rear drums and rear disc even if it's an EV or not it will still give you a little bit more breaking especially in an emergency!

 

I will not fight with you you are predetermined on why disc brakes are better....
Good luck and I hope some day you find time and try to learn more about drum vs disc.....EV vs ICE.....regeneration and other things that you are not very familiar with because of your esthetic preferences over engineering .

 

I will not fight with you you are predetermined on why disc brakes are better....

I remember reading Smokey Yunick and Cale Yarborough (NASCAR legends) arguing disc v. drums in the pages of Popular Mechanics magazine in the 1960s!

 

Just for grins, does anyone know the size of the front brakes compared to a GTI with the Performance Package?

A significant question: are the EU ID.4s equipped with the same drum brakes? These German cars are engineered to have superb brakes for panic stops from very high speeds on the Autobahn. If they can do it with rear drums, then I’m sure they are just fine.

 

Just for grins, does anyone know the size of the front brakes compared to a GTI with the Performance Package?

A significant question: are the EU ID.4s equipped with the same drum brakes? These German cars are engineered to have superb brakes for panic stops from very high speeds on the Autobahn. If they can do it with rear drums, then I’m sure they are just fine.
[/QUOTE
If the drum brakes are fine for you I'm happy for you but I was not saying that the car would not stop with drum brakes I'm saying that disc brakes will stop you better!

 

Wow - for a person that joined the forum 5h ago (and doesn’t even have the car) to rag on drum brakes (which make total sense since they hardly get used), they’ve certainly stirred things up. Unfortunately, for no good reason. Oh well…..some fall into the traps of these folks all the time. I think we’ve tried to answer the “subject line” of his post…..
I’m with VW Technician, he’s predetermined to have a certain view and nothing is going to change that (kind of like politics). 😂

 

He is challenging my facts and truth about disc vs drum....it will give more value and knowledge to others if we continue.... I have no problem exchanging engineering point vs car experienced enthusiasts that believe disc are superior engineering discovery .
So please keep your eyes open and you may learn something..

 

VW engineering determined that given the front disc brakes do most of the stopping, especially when coupled with the electric motor’s innate regenerative braking, that the rear brakes would be utilized far less than in an ICE vehicle. They were concerned that rear disc rotors would therefore surface flash rust even more so than ICE-normal. Having a drum effectively encapsulate the rear brakes was their solution to this consideration. It also doesn’t require periodic braking to clear the rotor and thereby doesn’t impede mileage efficiency.
Thankfully modern drum brakes have far better tolerances and materials technology than they did historically and are therefore quite robust when needed.
There’s no question that all other considerations aside disc brakes are somewhat more effective, but as just stated there were other considerations.
Let’s not bother discussing the relative degree of brake fade as this is a CUV and not a sports coupe and aside from Tanner Foust it will never be tracked.

 

And one important thing that EV makers don't discuss is low center of gravity that makes EV leaning with RWD choice instead of FWD almost not noticeable even at emergency stopping...that gives engineering more choices to have greater stopping on the rear end vs ICE car high gravity center and feeling of front end completely leaning down and taking valuable weight out of rear tires and making less stopping power in case of emergency stopping.

 

Continental drum brake

 

I don't think I can change the shoes like I did years ago..on that.

 

Quick little article that helps to explain the why….all sounds good to me….

Why the New Volkswagen ID.4 Electric Crossover Has Rear Drum Brakes

$40,000 is a lot of money for drums, but there's a good reason behind it.

www.thedrive.com

 

Arg, not to extend a thread that I thought was pretty complete 8 months ago, but here are some data points from recent Car and Driver track testing. Of course they are not testing for fade, but this would show the panic stop aspect. C&D does not say which ID.4 version they tested, but I'm thinking it was the First Edition which I think had slightly larger front disks than the Pro and Pro S.
(I have gleaned this from several pages, so no direct link. You can find their car reviews pretty easily)

 

So this would answer this discussion..... ID4 with drum brakes is on level of all around disc brakes....
So VW AG Engineering global platform not just for domestic US market is doing quite well....
Now if ID4 was equipped with performance tires like Tesla.... this would be much better.
Making equal comparison between two EV are not easy things to do.
In EU this testing are done from 100 km/h to 0 and there is additional safety that assist in panic braking where electronics take over even if user is not pressing hard on foot pedal.

 

give it a break, will ya.

 

Indeed. And as ElectricBlue well cites this thread was actually complete 8 months ago.
Let's now give this rear drum brake topic a break and move on to more pressing discussion issues.

Greenlineguy: We believe that the AWD model will also have rear drum brakes, having no data to the contrary, and also logically given more regenerative braking from the add'l front motor. Since as you've cited this rear drum brake is a deal breaker for you, all the best with whatever other EV you decide to procure. More EV's, regardless of flavor, is a good thing.

 

Well, heh, the guy (me) who didn't want to extend the thread is going to do just that one more time. Sorry about that. The first point was that my CDO* is making me want to update ChristophW's link early in the discussion which seems to have broken:
New VW ID.3 Model Drives Fully Connected, Safely and Far with Continental Technologies
It's down the page a bit, by the picture of the drum brake unit. It is focused on the ID.3 but should also apply to the 4.

In any case, reading through the paragraph, and maybe reading between the lines, seems to imply that this brake unit is electric? As in no hydraulics?? If it weren't so crazy hot and humid outside I would take the back wheel off to check.

I can think of no technical reason why an electric brake wouldn't be able to do the job. Many trailers use electric braking. But it sounds so weird... Anyway, my apologies if this has been discussed already. I did some searching, but often can miss things like that.

* CDO - It's like OCD, but the letters are in alphabetical order, as they should be!

 

Curious that they wrote "electric brake" but no, the ID.4 is most definitely hydraulic on all four corners.

There are electric brakes out there, but the only one I know off hand is the Boeing 787. It's simple but overbuilt to mash a whole stack of rotors together AND has to provide anti-skid capabilities at the same time it's acting like a bench vise. I don't think they could get that performance out of an inexpensive car part.