C8 brake question - drive by wire and the track...

[gthal]

As we know, the braking system on the C8 is a drive by wire, electronic brake system. Lots of reasons why this is a good move on the street. https://www.autoblog.com/2019/07/23/...stable-brakes/

My question is how will GM make this work for the track? Virtually no other track oriented cars use an electronic solution. The few cars that do give a warning light when the brakes get too hot. But, for those at the track, you know it doesn't work like that, necessarily. As the brakes get hotter, you can tell with fade and additional needed brake force. It allows you to manage the brake temps and it also lets you know how close you are to being outside of a safe operating window.

With the C8, if it's a brake temperature warning light, does that mean your lapping session is just done? You have no idea how hot the brakes are or how much actual fade you are getting. That would make it very tough to manage brakes on a track.

If this were the case, it will won't likely go over well with track enthusiasts and would likely be dangerous in practice. Personally, I just cannot see GM messing up the brakes in this car given its performance orientation. They have tested it extensively on the track from all of the videos. They know how critical the success of the car is and wouldn't mess with that. I bet it won't be an issue... HAVING SAID THAT, I can't see how they would manage this if the brake system is truly a drive by wire system without the analog feedback of heated brakes at the limit.

Thoughts?

[meyerweb]

Based on what I've read, the system provides feedback through the pedal proportional to the level of effort needed. So it could provide simulated feedback to the driver through the brake pedal. We'll have to wait and see.

The full C8.R race cars will not, I'm sure, use the brake by wire system at all.

[John]

I am far from knowledgeable about this new braking system. Does the C8 still have a brake master cylinder, brake lines, brake fluid, etc? Thanks for explaining.

[RoketRdr]

I am far from knowledgeable about this new braking system. Does the C8 still have a brake master cylinder, brake lines, brake fluid, etc? Thanks for explaining.

It does John but now it’s controlled by computer input instead of direct pressure from your foot. Think of the brake pedal of now being a potentiometer Instead of actually moving the fluid with your foot.

[Fasttoys]

Drove the Alfa Quad F with brake by wire and I was noT a fan. Hopefully they figured the programing which Alfa could not.

[John]

Thank you RoketRdr.

[C7Redneck]

Whoa. Thanks for bringing this to our attention. When GM went to electric steering I lost feedback from the tires to my fingers. Is this going to do the same to brake feel?

[meyerweb]

Whoa. Thanks for bringing this to our attention. When GM went to electric steering I lost feedback from the tires to my fingers. Is this going to do the same to brake feel?

Just for the sake of accuracy, the C7 doesn't have drive by wire "electric" steering. It has electric power assist, instead of vacuum assist, but the steering linkage is still recirculating ball.

[RoketRdr]

Drove the Alfa Quad F with brake by wire and I was noT a fan. Hopefully they figured the programing which Alfa could not.

Yeah I’m not a fan either. On the track you want to feel the brake modulation and feedback. I cant imagine that they’re able to program it in a way that you get feedback while tracking. Guess I will just have to wait and see but as for now I don’t think I’m gonna like it.

[RoketRdr]

Whoa. Thanks for bringing this to our attention. When GM went to electric steering I lost feedback from the tires to my fingers. Is this going to do the same to brake feel?

Unfortunately yes. They’re beginning to disconnect the driver from the machine and automate everything. I don’t like it from a racer standpoint but is fine for daily street driving. The steering isn’t as bad because they can create synthetic tactical feedback that at least lets your brain know when there’s tension or you’re on the edge. With the brakes I find it really hard to believe they can do the same. Brake pressure under your foot and kickback from the peddle is critical for track driving. Will have to see how well they “tuned” it and if there’s a disconnect from the senses. .

[gthal]

After researching/reading more on this, I'm not sure the description in the Autoblog article is 100% accurate. Clearly electronically assisted but maybe not a "drive by wire" system entirely.

[meyerweb]

I'm assuming it's the same system as in the Silverado and Sierra. There's some more detail here:

http://gmauthority.com/blog/2018/10/...verado-sierra/

As high-efficiency engines fail to produce enough vacuum pressure to generate the ideal amount of stopping power, German supplier ZF has introduced its answer. The 2019 Chevrolet Silverado and 2019 GMC Sierra are some of the first vehicles to benefit.

It’s called Integrated Brake Control (IBC) and it replaces the vacuum booster and associated cables, sensors, switches, electronic controllers and vacuum pumps. According to a Wards Auto report last Thursday, the system works with a pedal simulator. Fluid in the master cylinder is displaced to an accumulator and the system measures pedal travel. A motor with a ball screw then pushes a plunger to deliver hydraulic fluid to the wheels.

According to ZF, the motor can do all of this and generate brake pressure measuring 1 g in just 150 milliseconds. Automatic emergency braking is also quicker with IBC; the system can deploy full stopping force in a quarter of the time compared to a traditional braking setup.

Another benefit of the system is the ability to incorporate the electronic stability control in the one module. Thus, the 2019 Silverado and 2019 Sierra feature one package for the braking and stability control system. It also saves 11 pounds over traditional components.

ZF added it has contracts in place to provide the IBC system to eight vehicle platforms between multiple companies by 2020. Several more automakers plan to tap ZF for the technology, and there’s a very good chance we’ll see IBC also make its way to the next-generation Chevrolet Tahoe, Suburban, GMC Yukon and Cadillac Escalade. The SUVs will share the new full-size pickups’ T1 platform.

Read more: http://gmauthority.com/blog/2018/10/...#ixzz5vy3Z15HW

So maybe the motor assembly can also "push back" in proportion to the braking force? No idea, just speculating.

The ZF blurb says

• Normal brake pedal feel delivered through pedal simulation

So it seems like they've at least thought about the issue.

https://www.zf.com/products/en/cars/products_31680.html

https://press.zf.com/press/en/releas...ease_2995.html

Here's another. This one quotes ZF saying

The pedal input from the driver is interpreted by a hydraulic simulator, which provides the driver the feel of a traditional brake system. {also} Is it a type of brake-by-wire? ZF says that it is accurate to think of the IBC as a stepping stone toward fully dry brake-by-wire.

So not fully brake-by-wire.

https://thebrakereport.com/quick-hits-on-zfs-integrated-braking-control-system/

And from Wards Auto:

A test drive here of the all-new ’19 Chevrolet Silverado, which comes standard with IBC, confirms the prodigious braking capability as the calipers grab tightly in a panic stop, bringing the big truck to a sudden, jarring standstill. Otherwise, the pedal feel is natural and linear, providing progressive brake force that drivers will find familiar.

Of course, a pickup truck on the road and a Corvette on the race track are two very different things.

https://www.wardsauto.com/technology...c-contracts-zf

I guess all we can do is wait and see and hope for the best.

[Klinn]

Good info, thanks for posting.

[C7Redneck]

Lots of unanswered questions.

Is the pedal no longer mechanically connected to the master cylinder piston. Because a vacuum pump alone my not be an issue. Without a mechanical connection to the piston I don’t see how you would feel fade. We need a diagram!

If they have digital temp sensors on the calipers that are displayed that would be helpful.

I have not found specs on the Brembo Non Asbestos low Copper pads yet.

Wonder what happens to track rats who need more higher temp range and put high temp track pads on this system?

Will this same eboost be on a ceramic offering for the Z06?

[C7Redneck]

Just for the sake of accuracy, the C7 doesn't have drive by wire "electric" steering. It has electric power assist, instead of vacuum assist, but the steering linkage is still recirculating ball.

Good to know! Based on the loss of feel I thought it was electric steering.