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Billyk24

Billyk24

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have 12" brake rotors and they are enough to be safe. No more -----Please document that your Y has only 12 inch brake rotors. Don't post your CAD photos for such.
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What I am trying to do is point out an obvious and serious flaw that I hope will be fixed prior to full production.
Have you sat in an actual production Mach E and tested the brakes to call it a "flaw"?
 

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Good point, you know who has tested the Mach-E....Ford engineers.

No way the vehicle will be unsafe or not worthy of the Mustang name.
Having seen Dave Pericak on Leno's Garage and various interviews, I'm 100% convinced the man knows how to make a Mustang. I don't think he would allow the Mach-E to bring the pony icon down.
 
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I drive a car that is 600 pounds lighter than the E. ----The E can actually be lighter than the Y. Depends upon specifications/model. He continues to post incorrect information about the Y and the E and can not document what he is stating.
 


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Have you sat in an actual production Mach E and tested the brakes to call it a "flaw"?
I don't need to. I've driven enough cars to know how well 10" brake rotors do with a 5000 pound car. Ask yourself this: why does Tesla use 12" brake rotors on a 4400 pound car? Is it because they just spend money and everything in the Y is way overbuilt? Or is it because it needs 12" brakes? Why does Ford equip the Mustang GT500 with 16.5" brakes? Wouldn't 10" brakes do just as well? Here is reality, and everyone who knows anything at all about cars knows this: 10" brake rotors are not sufficient for a 5000 pound car, let alone one with the power of the Mach-e.
Having seen Dave Pericak on Leno's Garage and various interviews, I'm 100% convinced the man knows how to make a Mustang. I don't think he would allow the Mach-E to bring the pony icon down.
I hope you are correct and they fix the brakes. The example shown on this thread is a fail. Period. I hope those brakes don't make it to a production vehicle because people will die if they do.

Is there not another person here who understands brakes even a little bit??? What worries me is Ford product managers are reading this thread and getting the impression that they can cut corners where they shouldn't.

You know what's funny, so many folks on here slam "Tesla Fan boys", and yet nobody on TMC, not one person, is defending the heavy weight of the 21" wheels on the Y. It's a flaw, and people accept it's a flaw. And that is absolutely NOTHING compared to the brakes shown on this thread. Reality check: the car on this thread is seriously, fatally flawed. Yet here on the Mach-e forum, not one other person will condemn brakes that are a serious safety issue. People make excuses. If there was a "T" on the hood and not a blue oval on the grill, y'all would rightfully be laughing and condemning this car. All you're doing is telling Ford you'll be fine with it if they build a POS. What worries me is that you might get what you're asking for.
 

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@Nak,

I suspect I'm like many others on here: not an automotive engineer, and not able to know if the concern you've raised is warranted or not.

You've made your point, and if Ford engineers see your concern and consider it as a legitimate issue, then I sure hope they'll do what's needed to keep people safe.

Anyway, I tried to educate myself on brake caliper sizing, but didn't get too far. I saw this video, which taught me that the way calipers and rotors are constructed are also important factors -- length of the caliper is not the whole story. But I can't draw any further conclusion than that given what little evidence is known and not understanding it, anyway. I am not a mechanical engineer nor in the automotive industry.
 

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Let me help y'all out a little bit with a really basic primer about how brakes work, since nobody seems to have any knowledge of this.

Brakes convert kinetic energy into heat. The brake calipers apply pressure on the brake pads which clamp onto the brake rotor. the friction slows the rotor and the kinetic energy of the car is converted into heat energy in the rotor. Energy can neither be destroyed nor created, it can only be transformed.

With an EV, we can take that kinetic energy, convert it into electrical energy which is then converted into chemical potential energy in the battery. This regen braking is great, but it has limitations. We can only convert kinetic energy at the fastest rate that we can charge the battery. If the battery is fully charged, we get zero regen braking. If the battery is cold, we get very limited regen braking. Even at it's best, with current technology, regen braking is only capable of a fraction of the braking force of conventional brakes.

When regen braking is insufficient for any reason, which will be the case under many circumstances, we must rely on conventional brakes. Our brakes have a limit to the amount of kinetic energy they can transform into heat and that limits our brakes capability to stop the car. As you use your brakes the rotors get hot and you experience brake "fade" which means your brakes progressively become less effective. (There are some very exotic, very very expensive brakes that do not fade with heat.) The limit of our brakes is defined as the amount of heat energy the rotor can absorb and disperse into the air. Bigger rotors increase our brakes capabilities in three ways. First and foremost bigger rotors have more mass and can absorb more heat than smaller rotors. Second, bigger rotors have more surface area and can therefore transfer heat faster to the surrounding air. Third, large brake rotors allow for larger pads which increases our maximum friction available if we design our brake system properly.

If you're thinking that maybe Ford is going use those exotic brakes I mentioned earlier, please give that idea up. The cost for those brakes isn't a few hundred more than conventional brakes, they're many thousands of dollars more expensive.

There is no "magic" Ford engineers can come up with to break the laws of physics. 10" brake rotors have been proven again and again to be insufficient for a 5000# vehicle like the Mach-e. They simply can't hold and disperse the heat energy required. Period. The slowest Mach-e will be a high performance vehicle that requires brakes equal to the task of slowing such a vehicle down multiple times in quick succession while fully loaded.

I have a 1992 Chevy blazer with 11.6" brake rotors. It weighs the same as the Mach-e. Empty with just me and gas in the tank the stock brakes are barely sufficient, if that. Poor brakes are a common complaint on this rig. You start getting brake fade on the second emergency stop from 60 mph. By the third application your stopping distance doubles. That's why I upgraded the brakes on that rig to 12.5" brakes. Now I don't get brake fade. Again, same weight as the Mach-e and 11.6" brakes weren't safe. 11.6" brakes are VASTLY superior to 10" brakes.

Even with 12" brakes the Mach-e would be under-braked. You're talking 600 pounds more than a Y; common sense tells you that you need bigger brakes on the Mach-e than on the Y. 12" would be OK, not great, but OK. 12.5" brakes would be excellent; equal to the Y given the different weights. 10"brakes aren't even a joke on the E. They would turn a great car into a POS death trap.
 

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@Nak, you may be right. What you are saying aligns with what I've been able to discern after consulting my Google Mechanic. That is, it's all about converting kinetic energy into heat.

That being said, I'm pretty confident that Ford has spec'd the vehicle appropriately and it'll stop in a safe amount of distance.

Guess we'll find out for sure on the sizing and performance before too long.
 

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OK yeah I understood all that except for the part where you are using some examples of other cars as rule of thumb for sizing the rotor to the vehicle's weight. This part is hard for me to grok because I still feel I'm missing details. For instance, I've got to believe that manufacturers building higher end cars in a competitive market are going to want to get top safety results from NHTSA and IIHS (and others). So I don't understand why they'd undersize rotors, if that is what happened.

My Fiesta has front disk brakes and rear drums. The rear brakes are barely used on my car, so I assume this is why this cost shortcut was taken.

In reviewing your math, I calculated the same size as you for the REAR disks, 10". But for the front, I am calculating them as roughly 12.7". Can you double check?

I used the close up of the rear wheel here: https://www.macheforum.com/site/threads/rapid-red-metallic-mach-e-club.85/post-4109

And the close up of the front wheel here: https://www.macheforum.com/site/threads/rapid-red-metallic-mach-e-club.85/post-5867
 
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Nak

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@Nak,
That being said, I'm pretty confident that Ford has spec'd the vehicle appropriately and it'll stop in a safe amount of distance.

Guess we'll find out for sure on the sizing and performance before too long.
You may be completely right; I hope you are. Hey, for all we know this particular vehicle is a test mule to gather data on braking capability with degraded brakes. It's pretty clearly instrumented and gathering data. Certainly you'd want to know how the car and the software would react with over heated brakes; it would be a lot easier to study that with brakes that have a limited ability to absorb energy. Just thinking that makes me feel better. :)
 

Nak

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Interesting. If that's true it would lend credence to the theory that this vehicle is a test mule for brakes. Why? The Brembo brake calipers in the link you shared are not the ones installed on this vehicle. If the brakes are a one off at this stage, they most likely are part of a test program.

Would you mind sharing your source for this?
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