I got a new '18 Grand Sport M7 and it feels like I'm activating the brake pre-application, like in BMWs. My previous car was a BMW 335i and it had brake pre-application feature where if you abruptly lifted your foot off the gas pedal, the computers (anticipating emergency braking) would apply brakes just enough remove any slack in the system and to make the the pads touch the rotors. When you finally touch the brake pedal, it feels nice and firm and brakes engage at the top of the pedal without the typical initial mushy travel.

I may have felt something similar a couple of times? Is that something C7s do?

 

I suspect you're feeling compression breaking. It slows the car down quite a bit when you lift. I've lifted thinking I'd roll to a red light only to have to give it gas to get there.

 

I'm saying, no, or it would have been touted somewhere along the line. Yes, for compression braking.

 

No, what I'm feeling is not compression braking (I will have another question later about it being lesser than what I'm used to). What I'm talking about is not the car slowing down, but about the brake pedal being firmer and brakes engaging at the top of the pedal without any pedal travel, unlike most normal circumstances otherwise where the brake pedal feels relatively mushy and has some pedal travel before the initial brake bite. I'm not saying that the brakes feel sloppy otherwise, just a relative comparison of the brake pedal feel when abruptly lifting off throttle and when not doing that.

I will try to reproduce this consistently and report back in a week or so.

 

Well, there is no pre-sense braking or other active braking that I'm aware of, or have heard of on here. If you are in fact experiencing stiff pedal and braking, and not compression braking, perhaps you have a caliper that's sticking. Aside from that, I can't imagine what it is that you're feeling. Z07 GS?

 

I have felt it occasionally, but I haven't been able to consistently reproduce it. I will keep an eye out for sticking caliper.

 

If it is not consistent and reproducible, then it’s not designed that way and not supposed to be happening IMO..

 

I noticed when I first got my C7 Z51 that it had literally no travel, this is my 6th Vette and had a CTS-V and Vsport with similar GM/Brembo brakes but those had that minute travel you mentioned. Though I did not feel it was a stuck caliper because there was no excessive dust on 1 wheel, excessive heat, disc wear or car pulling. I had been avoiding going to the track since I was pissing enough $ racing bikes but at 10k miles I did a short notice track day and just flushed brakes, still did not notice excessive pad wear etc during fluid flush. After track day and brakes overheating quickly even when turning all stability and traction systems off I decided to put new pads and rotors on. After removing pads it was visually apparent the upper pistons in the passenger rear caliper had been minutely sticking. All other pads measured consistent using digital calipers except those. That disc also had pad deposits after track day. After I put the new brakes on it now has the minute travel. I thoroughly cleaned all calipers and flushed the Castrol SRF I just put in out. Refilled with SRF and no problems since. No idea if your having the same issue but that was my experience. It was not visible till after the track day. Can't hurt to pull the pads out and push the pistons back and clean.

 

Thanks! I'm going to swap pads in a couple of days. Also, I've done one track day on the stock pads. I will measure the stock pads and see if there is any anomaly at any of the corners.

 

It's likely DFCO kicking in.

 

 

Reviving this dead thread because this sounds exactly how my car behaves. I think some people in this thread are misunderstanding the issue a bit. Did you ever find anything else out about this?

 

The C7 doe not have pre-braking, just well-designed brakes.

 

Necro thread of 3 years.