# new EV specific disc brake research by Continental



## MelindaV (Apr 2, 2016)

http://blog.caranddriver.com/inside...nks-disc-brakes-and-wheels-for-electric-cars/

Continental is developing a new aluminum disk brake specifically for EVs that otherwise see corrosion & rust issues from traditional iron rotors. 
But the very interesting thing is it is integral with the wheel instead of hub mounted.


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## garsh (Apr 4, 2016)

I would think that the easiest solution to the corrosion problem would be to switch to using an aluminum rotor.
Since EVs don't use the friction brakes often, overheating isn't as much of an issue.

Aluminum Rotors Vs. Cast Iron Rotors


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## MelindaV (Apr 2, 2016)

Continental’s other reasons for moving the rotor to the peremeter was to save weight and function quieter than traditional brakes


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## garsh (Apr 4, 2016)

MelindaV said:


> Continental's other reasons for moving the rotor to the peremeter was to save weight and function quieter than traditional brakes


The larger disc would be better at dissipating heat as well.

But requiring the disc to mount to the wheel is a non-starter for mass-market adoption.

Swapping wheels (as I do every winter and spring) would now involve removing & reattaching the brake caliper.
Might involve moving the rotor to the other set of wheels too, or paying for two sets of rotors.

If one of those wheels is a +1 size (as mine are now), the caliper will potentially need to be repositioned when swapping.
It's an interesting thought experiment.


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## Mad Hungarian (May 20, 2016)

As an engineering solution I think it's very cool.
As a guy who makes a living selling wheels I am horrified, as I suspect many of my colleagues around the globe are. But then again we're used to these periodic end-of-days pronouncements, witness the Tweel.
However let's discard the selfishness of the second statement and focus on what's going on here.
This very much resembles the multi-piece system used on heavy trucks and buses in the old days where the barrel/rim portion could be completely separated from the spoke and center section. This means you _can _have spare barrel sets mounted with winter or summer tires and swap them out just as easily as you do now, maybe even more easily due to the reduced weight of that segment.
However the real big downsides are:

- Minus-sizing would be ruled out completely, unless you change all the brake parts
- Plus-sizing would be very iffy as it would require spoke extensions from the barrel to reach the center section, freaking me out from a potential failure point
- You might only be able to make very minor changes to width or offset
- Changing the spoke/center design will likely be costly as it looks like a fully-forged affair
- It may work well for low performance economy EVs where braking requirements aren't that high, but might not cope in cars with Tesla-level performance, where big multi-piston brakes are currently required to deal with speeds/energy levels that can be attained.

It's certainly a much more viable tech than some of the crazier stuff I've seen floated over the decades, but in a world where EV manufacturers are fighting tooth and nail to achieve or beat cost parity with ICE (especially in the economy segment) I don't see it in the near term. 'Cause this just screams spendy.


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## Michel Cote (May 19, 2016)

Why this complex ? just use smaller disk that will be stressed enough not to rust.
It is the same problem having disks on rear wheel with fwd cars
I have rear drums (not sexy I admit) on my Insight and it's rust free less friction and did not need maintenance yet after 10 years.


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## SSonnentag (Mar 30, 2017)

Big money maker for shops rotating tires as they could charge five times more.


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## SSonnentag (Mar 30, 2017)

Mad Hungarian said:


> As an engineering solution I think it's very cool.


Yep, an engineering solution, but not a practical solution.


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## Rich M (Jul 28, 2017)

I think rotor rust issues could be solved with software. For example "apply brakes lightly for the first three decelerations after being parked for more than 6 hours regardless of pedal application"
It would be just enough to warm up the pads and rotors a little without sacrificing much efficiency.


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## Mad Hungarian (May 20, 2016)

Rich M said:


> I think rotor rust issues could be solved with software. For example "apply brakes lightly for the first three decelerations after being parked for more than 6 hours regardless of pedal application"
> It would be just enough to warm up the pads and rotors a little without sacrificing much efficiency.


Not a bad idea.
Interestingly there is a similar technology already in use by a number of higher-end manufacturers, automatic brake drying. The pads are lightly pumped on a regular basis in rainy conditions to prevent water buildup and the resulting lag in brake response, here's a summary of Cadillac's version.


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## Mad Hungarian (May 20, 2016)

SSonnentag said:


> Big money maker for shops rotating tires as they could charge five times more.


Actually no.
If you examine the diagram closely you'll note there's no more effort to remove or install the rim/tire section compared to a conventional wheel/tire, it's just that the center section and spokes stay in place. Same number of lugs used, just further away from the center.
Again, reminds me of the old Dayton modular truck wheels. Or even the 50's / early 60's VW Beetle wheels, where the massive brake drums served as a large part of the wheel "structure".


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## garsh (Apr 4, 2016)

Mad Hungarian said:


> If you examine the diagram closely you'll note there's no more effort to remove or install the rim/tire section compared to a conventional wheel/tire, it's just that the center section and spokes stay in place. Same number of lugs used, just further away from the center.


Oh! Yeah, I see that now.

You would just be stuck with one wheel design, but rim+tire swaps are just as easy.


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## SSonnentag (Mar 30, 2017)

Mad Hungarian said:


> Actually no.
> If you examine the diagram closely you'll note there's no more effort to remove or install the rim/tire section compared to a conventional wheel/tire, it's just that the center section and spokes stay in place. Same number of lugs used, just further away from the center.


I guess I'm failing to see any benefit to this design other than the rotor being aluminum, which I question the durability of in the first place. The only difference is the hub is larger. The wheel still bolts to the hub. The rotor still bolts to the inside of the hub. The caliper is on the inside of the rotor vs the outside, but that seems like a bad idea too. It has a smaller diameter, faster-rotating surface to scrub.


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## Mad Hungarian (May 20, 2016)

SSonnentag said:


> I guess I'm failing to see any benefit to this design other than the rotor being aluminum, which I question the durability of in the first place. The only difference is the hub is larger. The wheel still bolts to the hub. The rotor still bolts to the inside of the hub. The caliper is on the inside of the rotor vs the outside, but that seems like a bad idea too. It has a smaller diameter, faster-rotating surface to scrub.


I agree, weight savings not obvious or intuitive at first because you do have to have all the same components, just somewhat rearranged. The advantage all comes from the fact that the rotor is so much larger in diameter and positioned so much farther out from the center that you need far less clamping force to achieve the same amount of braking, which in turn allows all the components to be lighter.
Buell used this same idea extensively on their motorcycles, where it proved so efficient they only required one caliper/rotor to achieve the same braking performance as a conventional twin setup.


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## mkg3 (May 25, 2017)

Actually, disc brakes been a common use in passenger vehicles since the 70s and probably worth looking at a completely new way of braking EVs.

We've taken rotors and calipers to just about maximum of where they can go (e.g., ABS, carbon rotors,...). Given how little rotors and pads get used in EVs, composite carbon rotors may make sense, if we can get the costs more reasonable. No corrosion or durability issue. They're just expensive because its not produced, relatively speaking, in mass like iron rotors.

So if we say carbon rotors are the temporary fix, then new generation of braking system can be developed for EVs that incorporates regen braiking as an integral part of the system, rather than piled on solution.


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## Mad Hungarian (May 20, 2016)

mkg3 said:


> Actually, disc brakes been a common use in passenger vehicles since the 70s and probably worth looking at a completely new way of braking EVs.
> 
> We've taken rotors and calipers to just about maximum of where they can go (e.g., ABS, carbon rotors,...). Given how little rotors and pads get used in EVs, composite carbon rotors may make sense, if we can get the costs more reasonable. No corrosion or durability issue. They're just expensive because its not produced, relatively speaking, in mass like iron rotors.
> 
> So if we say carbon rotors are the temporary fix, then new generation of braking system can be developed for EVs that incorporates regen braiking as an integral part of the system, rather than piled on solution.


I second the motion. I've gotten the impression that we are still stuck in a situation where the creativity here is being stifled by costs, because there's been such an arms race to get MSRPs down before the market and entrenched interests try to write EVs off as too pricy to justify their existence without subsidies. Once we're there (2 - 3 years?) and more OEMs are in the game I think you'll see the R&D coffers open up to tackle things like old school brake technology.


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## Mad Hungarian (May 20, 2016)

Since we're on this weird subject and I'm a 20 year Audi veteran I feel obliged to post this.
Not a great first attempt, but impressive that they were on the case some 30 years ago...


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## Mad Hungarian (May 20, 2016)

Michel Cote said:


> Why this complex ? just use smaller disk that will be stressed enough not to rust.
> It is the same problem having disks on rear wheel with fwd cars
> I have rear drums (not sexy I admit) on my Insight and it's rust free less friction and did not need maintenance yet after 10 years.


If by stressed you mean so small that they would be used frequently and hard enough to stay corrosion-free, I think the problem is that they then wouldn't offer enough stopping power in a full blown emergency situation. I agree that drums would be better in this regard, but they have a terrible time recovering from repeated hard stops (take it from a former 16 yr old who drove his all-drum '75 Super Beetle like it was a 911 and is thankful to still be alive )


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## MelindaV (Apr 2, 2016)

Mad Hungarian said:


> Since we're on this weird subject and I'm a 20 year Audi veteran I feel obliged to post this.
> Not a great first attempt, but impressive that they were on the case some 30 years ago...


wouldn't that be more similar to a drum brake?


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## garsh (Apr 4, 2016)

MelindaV said:


> wouldn't that be more similar to a drum brake?


It looks kind of like a drum brake, but that's just so that the rotor is mounted from the outside edge instead of the inside edge.
Here's a picture of the back that makes it more clear.








Since the caliper goes on the inside, this "UFO rotor" can be big enough to just barely fit inside a wheel.
Nice!


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## AscendedSaiyan (Nov 7, 2016)

Mad Hungarian said:


> I second the motion. I've gotten the impression that we are still stuck in a situation where the creativity here is being stifled by costs, because there's been such an arms race to get MSRPs down before the market and entrenched interests try to write EVs off as too pricy to justify their existence without subsidies. Once we're there (2 - 3 years?) and more OEMs are in the game I think you'll see the R&D coffers open up to tackle things like old school brake technology.


Maybe ceramics would be a somewhat expensive way to solve the rust issue. What do you think?


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## Michel Cote (May 19, 2016)

By stressed, I mean smaller pad contact patch. You can have a big enough brake for 2-3 emergency situations in a row no problems.
Smaller just enough so the disk surface ''feel'' the same pressure/friction as if it were in a ice car.

Maybe just reformulation of the pad composition would suffice.

for example brake can absorb something like 500kW but battery just 125kW (just to have round numbers)
So a 75% as big brake should be ok the 25% going in the battery.
The problem is that in real life 125Kw will take care of 90% of the braking, almost no mechanical breaking.

Like someone said, a good solution would be to prohibit regen braking for 3-5 braking cycles in the morning.


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## Mad Hungarian (May 20, 2016)

AscendedSaiyan said:


> Maybe ceramics would be a somewhat expensive way to solve the rust issue. What do you think?


Yeah, at this stage they are still very, very pricey. Not sure we're going to see that option come into play for entry level vehicles unless there's some big breakthrough in the technology.


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## AscendedSaiyan (Nov 7, 2016)

Mad Hungarian said:


> Yeah, at this stage they are still very, very pricey. Not sure we're going to see that option come into play for entry level vehicles unless there's some big breakthrough in the technology.


I'm thinking aftermarket, like Brembo.


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## Mad Hungarian (May 20, 2016)

AscendedSaiyan said:


> I'm thinking aftermarket, like Brembo.


Do you mean as in an aftermarket conversion kit? I can't see anyone spending the money ('specially with most EV owners being something of a frugal bunch) as you would probably be able to replace the stock iron rotors at least 5 times over (labor included) for the cost of a ceramic conversion kit. Being that most EVs will never need more than one or two sets of iron rotors in their life I don't think the ROI is there.


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