[rotis]

Originally Posted by TrackClub

- the issue seems to manifest itself at autox courses only, specifically when rears are still spinning while brakes are hammered, perhaps also with bumps involved

Wheelspin-to-brakes would be classified as a "speed error", it is one possible cause of hard pedal. It is a common driver-induced issue going back as far as the c5z (in my experience) and is fairly easy to avoid. Trying to brake over bad bumps, and getting hard pedal is somewhat understandable. Neither of these are particularly egregious, nor are they unique to the Gen6.

Originally Posted by TrackClub

- 1LE cars seem less (if at all) prone to this issue

Less prone for sure. The ZL1-1LE in particular was tuned on the factory R-Comps and is the most resilient.

Originally Posted by TrackClub

- by and large only heavily modded cars are prone to this issue

If you put RE71Rs on an otherwise completely stock 2016-2018 Camaro SS, you'll get a rock hard pedal at autocross any time there is a slalom exit too close to a braking zone, regardless of how smoothly you apply the brakes. It is the premature slippage of the still-unloaded inside front tire that triggers split-mu detection. This condition results in 750 milliseconds (3/4 sec) of "WHAT THE ****!". It might not sound like a long time, but when you're coasting through a braking zone at an autocross while standing on the brakes as hard as you possibly can, it feels like an eternity.

What is the real purpose? Well, if you are driving on a two-lane road and you dip two tires into the dirt on the side of the road, you are in a split-mu situation. If you slam on the brakes in a panic, the car will stay straight because it heavily restricts the braking power being applied to the tires that still have grip. If it didn't, you would yaw into oncoming traffic. This is split-mu and most trims of the Gen6 are (imo) overly sensitive to it.

Originally Posted by TrackClub

- changing driver inputs (even slightly - per Tadge) prevents the issue (and agrees with my own experience with my previous car)

I've autocrossed a lot of cars, including the C7 and even open-wheelers with no ABS. I am not a gorilla on the pedals. The C7 hard pedal (Tadge's team) can happen under the same conditions, but it is not nearly as severe as the Gen6 Camaro. It feels like it doesn't hold back as much pressure, so even when it does happen it's not nearly as bad.

Originally Posted by TrackClub

- no reported issues at road circuits even with modified cars incl slicks and/or race brake pads.

It is nearly impossible to trigger split-mu under normal conditions on a racetrack, because braking zones generally don't start in the middle of corners.

Anyhow, the folks on team Camaro put real effort into addressing it for 2019. Is it perfect? probably not, but I bet it's significantly better.

[HawkeyeMike]

I really like all this conversation. One thing from the last several posts is sitting strange with me. Unless ABS has the ability to manifest itself in multiple ways, I'm convinced that this isn't ABS activating. I know what ABS activation feels like - there is a fast modulating feel coming off the brake pedal, you can hear the sounds it makes at the brakes as they modulate on/off fast, and the pedal feels a bit softer if anything.
This issue...there is no modulation, no sound, no softening...just a harder brake pedal and the car simply doesn't stop. It really feels like the power assist is removed.

Mike

[Nick S]

Originally Posted by HawkeyeMike

I really like all this conversation. One thing from the last several posts is sitting strange with me. Unless ABS has the ability to manifest itself in multiple ways, I'm convinced that this isn't ABS activating. I know what ABS activation feels like - there is a fast modulating feel coming off the brake pedal, you can hear the sounds it makes at the brakes as they modulate on/off fast, and the pedal feels a bit softer if anything.
This issue...there is no modulation, no sound, no softening...just a harder brake pedal and the car simply doesn't stop. It really feels like the power assist is removed.

Mike

It is most definitely the ABS module causing the hard pedal. It can and does have multiple ways it can take action. As I suggested before find the fuse for your ABS and unplug it for an Autocross and see if you still run into the issue. Or if you get a new issue such as locking up the front tires.

[TrackClub]

Rotis: good comments.

Per my link ive included (unrelated to GM and addressing a race vs street system), ABS also manages stability, hence it likely relies on prevailing yaw angles not unlike Stabilitrak. In other words, perhaps, it won't engage if parms tell it that any F brake will result in a spin. Or something to this effect. This would be consistent with present dynamics re weight transfer if somebody added tons of throttle then immediately hammered brakes in a very tight mid corner. This would also be consistent with GM not wanting to permit such "flexibility" for street driven vehicles as regular drivers would very likely completely lose control.
I like Chris V's suggestion as to solution. Pulling a fuse is another choice albet i suspect that would also require a driver mod not to flat spot the tires and/or spin.
If indeed GM dialed things differently in a 19MY that's also great.
In summary, various electronics permit modern drivers to pay less attention to weight transfer and balance.
That's not necessarily a bad thing per se, but any system has its limits which has to work within laws of physics (and designed safety parms which are the prime reason for such systems).
This may not be unlike somebody driving with Stabilitrak on, yet completely overdriving the car and managing to spin out and then complaining the system isn't doing its job. Unfortunately miracles dont happen.

[vtirocz]

Originally Posted by Chris V

If you want to add the 19+ calibration to your 2017-2018 (but not 2016) car, you can, but it's not easy. You need the brake controller off of a 19+ car with the same brake configuration. It's plug and play, but that requires pry bars and pulling the cowl, in addition to getting a computer with the calibration on it.

Can you elaborate on this procedure? I've never experienced the problem, but interested in this solution

[HawkeyeMike]

Originally Posted by rotis

If you put RE71Rs on an otherwise completely stock 2016-2018 Camaro SS, you'll get a rock hard pedal at autocross any time there is a slalom exit too close to a braking zone, regardless of how smoothly you apply the brakes. It is the premature slippage of the still-unloaded inside front tire that triggers split-mu detection. This condition results in 750 milliseconds (3/4 sec) of "WHAT THE ****!". It might not sound like a long time, but when you're coasting through a braking zone at an autocross while standing on the brakes as hard as you possibly can, it feels like an eternity.

What is the real purpose? Well, if you are driving on a two-lane road and you dip two tires into the dirt on the side of the road, you are in a split-mu situation. If you slam on the brakes in a panic, the car will stay straight because it heavily restricts the braking power being applied to the tires that still have grip. If it didn't, you would yaw into oncoming traffic. This is split-mu and most trims of the Gen6 are (imo) overly sensitive to it.

This! You hit the nail on the head, and matches my experience perfectly. So it isn't about the rears sliding...it's about the inside front still unloaded from the slalom exit. Makes sense, as I think back to last event. The 'straight' that I mentioned was really just a long high speed slalom. The last motion before the corner was a slight right turn to finish the slalom. Then hard brakes for the right hand corner. The front right was still 'light' at the time of hard braking.

So, the fix may be to back up the final slalom 'turn' a bit, ensure the car is more evenly loaded before braking. I will try this too.

Thanks!
Mike

[apexit53]

Originally Posted by rotis

If you put RE71Rs on an otherwise completely stock 2016-2018 Camaro SS, you'll get a rock hard pedal at autocross any time there is a slalom exit too close to a braking zone, regardless of how smoothly you apply the brakes. It is the premature slippage of the still-unloaded inside front tire that triggers split-mu detection. This condition results in 750 milliseconds (3/4 sec) of "WHAT THE ****!". It might not sound like a long time, but when you're coasting through a braking zone at an autocross while standing on the brakes as hard as you possibly can, it feels like an eternity.

exactly this!

At nats last year there were a few of those zones and i just felt "this is where im losing time to the M3"

[TrackClub]

Originally Posted by HawkeyeMike

This! You hit the nail on the head, and matches my experience perfectly. So it isn't about the rears sliding...it's about the inside front still unloaded from the slalom exit. Makes sense, as I think back to last event. The 'straight' that I mentioned was really just a long high speed slalom. The last motion before the corner was a slight right turn to finish the slalom. Then hard brakes for the right hand corner. The front right was still 'light' at the time of hard braking.

So, the fix may be to back up the final slalom 'turn' a bit, ensure the car is more evenly loaded before braking. I will try this too.

Thanks!
Mike

This is an excellent point by Rotis (must admit i have missed its full merit on a first read). However, dont discount the rears spining from contributing to the problem as ABS controls each wheel independently to ensure *safe yaw* angles (such as in Rotis' example of 2 different surfaces). So, if the rears are spinning the yaw will increase (lack of traction plus steering lock) and likely exasperate the problem that ABS is trying to deal with in the first place up front. Meaning split MU up front PLUS excessive yaw = perfect storm scenario.

[TrackClub]

Just an fyi re pulling a fuse on ABS: it may not be a good idea just in case a proportioning valve is located within this module as is the case in some cars.
Dont know about the Camaro specifically.

[Norm Peterson]

Perhaps unplugging a wheel sensor or two would leave any proportioning still in place?

I'm only guessing here, based on the module still getting power and only not knowing how fast one or more wheels are rotating. It's at least an alternative should these cars have the proportioning built into the ABS module, and I would hope that proportioning would not be sacrificed by design during the easily predictable loss of a sensor or continuity in its wiring.


Norm

[TrackClub]

Originally Posted by Norm Peterson

Perhaps unplugging a wheel sensor or two would leave any proportioning still in place?

I'm only guessing here, based on the module still getting power and only not knowing how fast one or more wheels are rotating. It's at least an alternative should these cars have the proportioning built into the ABS module, and I would hope that proportioning would not be sacrificed by design during the easily predictable loss of a sensor or continuity in its wiring.


Norm

This might be an option, but i suspect ECU would throw a code and put motor in limp mode if proportioning got disabled. Some cars do it when wheel sensor goes as well. I think there is a possibility this might be a bit complex unless one fully understands all electronic interdependencies bulit into the system. A subject i know nothing about.

[Norm Peterson]

You would, of course, get the ABS light.

I don't know whether that would invoke 'limp mode' or limit power in a Camaro either, although getting the ABS light in the Mustang at the track didn't seem to affect anything else, nor did having a sensor in one of our other cars die.


Norm

[wnta1ss]

Originally Posted by TrackClub

This might be an option, but i suspect ECU would throw a code and put motor in limp mode if proportioning got disabled. Some cars do it when wheel sensor goes as well. I think there is a possibility this might be a bit complex unless one fully understands all electronic interdependencies bulit into the system. A subject i know nothing about.

Don't know about proportioning, but I have removed the ABS fuses (2 of them) on the dragstrip and the motor ran fine. The power steering does not work either when this is done. I had found that even turning off Stabilitrack with the long hold of the T/C button did not completely stop Stabilitrack, hence this experiment. Obviously there would be a lot more things to worry about trying this on an autocross, or particularly a road course, and I would not be so quick to try it for such events.

[BlueinTN]

Originally Posted by TrackClub

Rotis: good comments.

Per my link ive included (unrelated to GM and addressing a race vs street system), ABS also manages stability, hence it likely relies on prevailing yaw angles not unlike Stabilitrak. In other words, perhaps, it won't engage if parms tell it that any F brake will result in a spin. Or something to this effect. This would be consistent with present dynamics re weight transfer if somebody added tons of throttle then immediately hammered brakes in a very tight mid corner. This would also be consistent with GM not wanting to permit such "flexibility" for street driven vehicles as regular drivers would very likely completely lose control.
I like Chris V's suggestion as to solution. Pulling a fuse is another choice albet i suspect that would also require a driver mod not to flat spot the tires and/or spin.
If indeed GM dialed things differently in a 19MY that's also great.
In summary, various electronics permit modern drivers to pay less attention to weight transfer and balance.
That's not necessarily a bad thing per se, but any system has its limits which has to work within laws of physics (and designed safety parms which are the prime reason for such systems).
This may not be unlike somebody driving with Stabilitrak on, yet completely overdriving the car and managing to spin out and then complaining the system isn't doing its job. Unfortunately miracles dont happen.

yes pulling the ABS fuse isnt that simple it effects all the stability systems. Wish it was everyone would be doing it.


Now if it was 1989 and your GMC truck has an ABS light on...yep pull the ABS computer plug and keep rolling.


I just hope I never experience it myself that part Im not really interesting in "learning" about ice mode just reading about it.