[phdibart]

I'm doing a brake job, and I've pretty much decided to go with Brembo rotors and Akebono ACT pads. I have a 2015 2.0L ATS base trim without the performance pads, currently at around 68k miles. Does anyone have experience with this rotor/pad combo? I've read Akebono was this supplier of factory pads, and they have an awesome reputation (as well as Brembo), so I figured I couldn't go wrong. I'm looking for factory performance, not an upgrade, as this is my daily driver.

A followup question is, should I replace the front rotors? I planned on doing just the rear rotors with new pads all around. My current rear rotors have a lip, but the front rotors are smooth as can be with no grooves. It's my understanding that traction control systems use the rear more heavily, so I figure that's why the rears are more worn.

 

[rsingl]

I would leave the front rotors alone if there is minimal wear on the pad swept area as it appears. In the recent past, it was normal for rear brakes to wear far more slowly than fronts but some designs, including apparently the ATS, went overboard when accounting for the lesser amount of braking done by the rear. In heavier stops, there is tremendous weight transfer to the front where the majority of the braking force occurs and for most cars the front end is far heavier so even in moderate stops the front still does most of the braking but with a car like the ATS which has excellent front to rear weight balance, in normal braking the rear brakes do a lot of the work. Reducing rear brake system weight is one of the ways that manufacturers cut overall vehicle weight for fuel efficiency and unsprung weight for better handling and the result is often faster wear. Minimizing platform weight was a huge design factor with the ATS both as a goal but also a learning design exercise and GM got pretty creative but ended up with an excellent platform, that sort of design thought reflects the best of GM and what their very talented engineers are capable of doing when the corporate environment allows.

Only in extreme cases will TCS apply braking to the rear wheels. TCS works first by retarding timing to fine tune power delivery on the fly and follows up by commanding the throttle plate further closed to reduce torque if necessary. Rear brakes are applied selectively when only one tire is losing traction or when stabilitrak needs to pull the car back in line but for most drivers the amount of added brake wear from this is minimal. I suspect that your rear rotor wear is just the result of the calculated braking design and proportioning valve setup maybe coupled with overly aggressive rear friction material. I have used Akebono pads on another car and they were of good quality, my only caution when replacing brake pads is to make sure that the friction material selected isn't going to cause excessive noise or brake dust. Brake dust is a huge pain (speaking as a Z06 owner) and if not removed regularly will pit the wheel finish.

Rodger

 

[phdibart]

rsingl, thanks for the input!

 

[rsingl]

rsingl, thanks for the input!

You are welcome!

For those new to the ATS, there used to be an interesting document online from GM engineering with graphics and explanations of some of the methods used to reduce Alpha platform body weight but it seems to have disappeared. I saved it some time back while it was still available but the PDF is too large to allow attachment at this site. I will upload it later this week to Google drive or dropbox and provide the link.

Rodger

 

[jeffbazell1]

I have the Akebono front pads which I did myself at 77,695 miles. I'm now at 100,600 miles and the brakes are still as smooth as honey. I had already had a four-rotor sanding done about 40K miles ago and no problems yet. I'm about ready to do the rear pads. I would say not to do anything to the rotors unless you notice any pulsation when braking hard from a fast speed. When I replaced my front pads, they still looked new. Probably didn't even need new ones yet but I figured at 77,695 it was good preventive maintenance. Easy job, too.

 

[The Black Stig]

1. The OEM pads are brembos pads are relabeled acdelco.

2. The cost of OEM rotors are extremely cheap $70~ per side front and half that for the rear. I would personally replace them unless you live below the rust belt, and look nearly perfect my main concern is ventilation channels being clean. I would reuse used OEM rotors wayyy before I ever use the local auto store crap. Fixed calipers do not like runout.

3. I use a set of akebono on my rear big brembo setup, they work great however the do promote a lot of heat transfer. Street car should be fine.

 

[The Black Stig]

I would leave the front rotors alone if there is minimal wear on the pad swept area as it appears. In the recent past, it was normal for rear brakes to wear far more slowly than fronts but some designs, including apparently the ATS, went overboard when accounting for the lesser amount of braking done by the rear. In heavier stops, there is tremendous weight transfer to the front where the majority of the braking force occurs and for most cars the front end is far heavier so even in moderate stops the front still does most of the braking but with a car like the ATS which has excellent front to rear weight balance, in normal braking the rear brakes do a lot of the work. Reducing rear brake system weight is one of the ways that manufacturers cut overall vehicle weight for fuel efficiency and unsprung weight for better handling and the result is often faster wear. Minimizing platform weight was a huge design factor with the ATS both as a goal but also a learning design exercise and GM got pretty creative but ended up with an excellent platform, that sort of design thought reflects the best of GM and what their very talented engineers are capable of doing when the corporate environment allows.

Only in extreme cases will TCS apply braking to the rear wheels. TCS works first by retarding timing to fine tune power delivery on the fly and follows up by commanding the throttle plate further closed to reduce torque if necessary. Rear brakes are applied selectively when only one tire is losing traction or when stabilitrak needs to pull the car back in line but for most drivers the amount of added brake wear from this is minimal. I suspect that your rear rotor wear is just the result of the calculated braking design and proportioning valve setup maybe coupled with overly aggressive rear friction material. I have used Akebono pads on another car and they were of good quality, my only caution when replacing brake pads is to make sure that the friction material selected isn't going to cause excessive noise or brake dust. Brake dust is a huge pain (speaking as a Z06 owner) and if not removed regularly will pit the wheel finish.

Rodger

Technically stabilitrack (stability control) is what cause the brakes to activate and grab and make minute corrections, TCS just keeps the wheels from spinning by closing the throttle body or rather giving you 20% open vs 100%open ( and up shift on auto cars)

If you turn TCS off you can chrip the tires, peel out, & even do mild burn outs. But the minute any steering angle is introduced or the yaw sensor and computer don't like like your slip angle stabilitrack will rein you back in line.

 

[carguy2015]

You can't go wrong with Akebono pads. Stopping is smooth as butter and no offensive dust powder whatsoever. Best of all, Akebono pads require no bedding in which perhaps explains why they supply OEM pads to a little over 30 percent of the world-wide automobile market. I've got Akebono's on my Mercedes and have not experienced any heat issues as described by The Black Stig. When it's time to do my first brake job on the ATS, the replacement pads will definitely be Akebono's.

 

[rsingl]

Stig,

From GM standard boilerplate text:

"Traction Control System (TCS)


The vehicle has a Traction Control System (TCS) that limits wheel spin.


On a front-wheel-drive vehicle, the system operates if it senses that one or both of the front wheels are spinning or beginning to lose traction. On an All-Wheel-Drive (AWD) vehicle, the system will operate if it senses that any of the wheels are spinning or beginning to lose traction. When this happens, the system brakes the spinning wheel(s) and/or reduces engine power to limit wheel spin.


The system may be heard or felt while it is working, but this is normal.


TCS is on whenever the vehicle is started. To limit wheel spin, especially in slippery road conditions, the system should always be left on. But, TCS can be turned off if needed."

Selective brake application is done for BOTH Stabilitrak and TCS. For TCS, it allows an open differential to behave more like a limited slip differential by providing some load to the freely spinning wheel so that increased torque is available to the wheel with traction.

This sort of TCS system is why you see reduced availability of limited slip differentials in passenger cars and because a regular limited slip causes "interesting" steering and control characteristics when used as part of the steer axle that system wasn't used in regular passenger cars.

Rodger

 

[robertorolfo]

You can't go wrong with Akebono pads... When it's time to do my first brake job on the ATS, the replacement pads will definitely be Akebono's.

Yes, Akebono are a good brand, but Brembo are the OEM spec and Brembo are the world leader in brakes, so...

 

[The Black Stig]

Stig,

From GM standard boilerplate text:

"Traction Control System (TCS)


The vehicle has a Traction Control System (TCS) that limits wheel spin.


On a front-wheel-drive vehicle, the system operates if it senses that one or both of the front wheels are spinning or beginning to lose traction. On an All-Wheel-Drive (AWD) vehicle, the system will operate if it senses that any of the wheels are spinning or beginning to lose traction. When this happens, the system brakes the spinning wheel(s) and/or reduces engine power to limit wheel spin.


The system may be heard or felt while it is working, but this is normal.


TCS is on whenever the vehicle is started. To limit wheel spin, especially in slippery road conditions, the system should always be left on. But, TCS can be turned off if needed."

Selective brake application is done for BOTH Stabilitrak and TCS. For TCS, it allows an open differential to behave more like a limited slip differential by providing some load to the freely spinning wheel so that increased torque is available to the wheel with traction.

This sort of TCS system is why you see reduced availability of limited slip differentials in passenger cars and because a regular limited slip causes "interesting" steering and control characteristics when used as part of the steer axle that system wasn't used in regular passenger cars.

Rodger

1. Cars that use rear brakes as an lsd are usually marked ELSD
2. There is several levels of TCS what I described is what happens on the ats confirmed by a scan with live data.

 

[The Black Stig]

You can't go wrong with Akebono pads. Stopping is smooth as butter and no offensive dust powder whatsoever. Best of all, Akebono pads require no bedding in which perhaps explains why they supply OEM pads to a little over 30 percent of the world-wide automobile market. I've got Akebono's on my Mercedes and have not experienced any heat issues as described by The Black Stig. When it's time to do my first brake job on the ATS, the replacement pads will definitely be Akebono's.

I should clarify my use of akebono pads were on the track, as stated street use is more than fine and they are my go to pads where OEM pads aren't a feasible option.

2. I 100% disagree that they do not need to be beeded in. They do, however you don't need to do anything special but drive on them normally. After week or so you will see the film transfer on the rotors and performance SHOULD be improved. However I would absolutely NOT go out and hammer on the brakes.

 

[rsingl]

From GM concerning the eLSD system used in Corvette and a limited number of Camaro trims, it is implemented through electronic control over hydraulically actuated clutches within the differential. Many AMG trim Mercedes models have a similar eLSD setup. BMW tries to use eLSD as a marketing term for their brake type system but it in no way compares to a true eLSD in performance or design but it simply an inexpensive way to gain some of the performance attributes of a true limited slip differential:

The 2017-2019 Camaro ZL1 and Camaro SS 1LE; 2018-2019 Camaro ZL1 1LE; and 2015-2019 Corvette models equipped with the 6.2L V8 engine (RPOs LT1, LT4, LT5) feature an Electronic Limited Slip Differential (eLSD) system (RPO G96).
The eLSD system, which is available on a limited number of performance vehicles, provides an open differential when needed and a locked differential when conditions call for it.

The system is capable of adjusting the coupling from fully open to fully locked in as little as 0.15 seconds.
The eLSD system has an incredible effect on the vehicle’s performance and handling.
When the driver is off the throttle, more eLSD coupling adds stability, to a point.

When the two rear wheels are clutched together in a turn, the outside wheel is slowing down and the inside wheel is speeding up in order to provide an agile feel throughout the turn.
When the driver is on the throttle, the eLSD system can shift the torque from the inside wheel to the outside wheel to minimize inside wheel spin. The right amount of torque applied to the outside wheel will help the car turn.

eLSD Operation

The rear differential clutch control module controls the eLSD operation.
When the rear differential clutch control module receives a torque command signal from the chassis control module (CCM), it actuates the differential clutch pump and rear differential clutch solenoid valve.

The electro-hydraulic piston actuation engages the limited slip clutch to allow active variable locking torque transfer to the left and right half shafts.
There are many different algorithms, or calculations used by the eLSD system.
The amount of coupling that the system delivers depends on many different factors, including vehicle speed, throttle position, steering angle, yaw rate, available traction, vehicle options, and Performance Traction Management (PTM) mode.

Each vehicle package is tuned or calibrated individually. As a result, the operation is not exactly the same between a Corvette Z06 and a Corvette Stingray with the Z51 package. Vehicles equipped with automatic and manual transmissions also have different eLSD calibrations, as do cars equipped with different suspension and tire combinations.
TIP: When diagnosing a perceived fault with this system, it’s critical to obtain very specific information from the customer and, if a comparison vehicle is used, the car must have exactly the same options.
eLSD Coupling Percentage
An open differential has a 0% coupling percentage while a locked differential is 100%.

Driving straight down the road, the eLSD system will have a bit of coupling to add stability and on-center steering feel (around 10% – 15%), which will decrease slightly when making a lane change or other steering input. Under heavy acceleration in a track setting, the system will increase to around 40-50% coupling in order to maximize rear traction while cornering,
During the most aggressive dynamic maneuvers, such as extreme lane changes and slalom events, the largest coupling will occur.
The eLSD clutches will nearly lock (100%) to add stability at the right moment but open back up to allow the vehicle to steer through a double lane change at precisely the right times.

If the vehicle is being driven in the winter (equipped with the appropriate tires), accelerating from a stop with one wheel on ice and the other on dry pavement, the clutch torque will increase on the DIC as a result of the single wheel slipping. Torque will be transferred to the wheel with more available traction.

Because the eLSD system is filled with fluid, small amounts of air will accumulate in the system over time
. A small actuator is built into the system in order to bleed air from the system. The bleed cycle will run after every third key cycle with a minimum key off soak time of 30 minutes.
While the bleed process is running, a buzzing or whirring noise may be audible and the coupling percentage on the DIC may spike up to 100% briefly while driving at very low speeds and in a straight line. This is normal operation and does not indicate a problem with the system.

TIP:

Any time a hydraulic line to the eLSD system is opened, a service bleed procedure with a scan tool needs to be performed to remove any air from the system.
Wheel Slip Percentage
The DIC screen also shows wheel slip, which is the white number on a 0-30% scale.
The wheel slip percentage informs the driver as to how much rear wheel slip the vehicle is currently experiencing.

In order to help prevent misdiagnosis when dealing with customer questions on this reading, it’s important to remember that this graph has nothing to do with the eLSD system. It is an independent calculation and is not an indication of the slip inside the eLSD clutches.

The percentage of wheel slip is calculated by using the average of the rear wheel slip as compared to the average of the front wheel slip.
The data is generally not accurate below vehicle speeds of 20-30 mph (32-48 km/h), so when driving at slower speeds, the graph may briefly max out at 30%
.
This is normal operation.
For example, if the front wheels are traveling at 2 mph (3 km/h) and the rear wheels are showing 3 mph (5 km/h), this indicates a 50% difference in speeds.
Since the graph is capped at 30%, the bar graph will max out in this type of scenario.

When traveling at these speeds, actual wheel slip will not be felt by the driver, even though it appears drastic on the graph. This is simply the result of the math behind the system.

And verbatim from page 9-33 of the 2014 ATS owner's manual:

"TCS activates if it senses that any
of the drive wheels are spinning or
beginning to lose traction. When this
happens, TCS applies the brakes to
the spinning wheels and reduces
engine power to limit wheel spin."

TCS uses both engine torque reduction (along with "short shifting" of auto equipped vehicles) AND braking to control wheel spin. Applying some braking force to the wheel without traction allows far -better acceleration than relying just upon engine power reduction to control wheel slippage which is why TCS uses both.

Rodger

 

[Sergio526]

Stig,

From GM standard boilerplate text:

"Traction Control System (TCS)


The vehicle has a Traction Control System (TCS) that limits wheel spin.


On a front-wheel-drive vehicle, the system operates if it senses that one or both of the front wheels are spinning or beginning to lose traction. On an All-Wheel-Drive (AWD) vehicle, the system will operate if it senses that any of the wheels are spinning or beginning to lose traction. When this happens, the system brakes the spinning wheel(s) and/or reduces engine power to limit wheel spin.


The system may be heard or felt while it is working, but this is normal.


TCS is on whenever the vehicle is started. To limit wheel spin, especially in slippery road conditions, the system should always be left on. But, TCS can be turned off if needed."

Selective brake application is done for BOTH Stabilitrak and TCS. For TCS, it allows an open differential to behave more like a limited slip differential by providing some load to the freely spinning wheel so that increased torque is available to the wheel with traction.

This sort of TCS system is why you see reduced availability of limited slip differentials in passenger cars and because a regular limited slip causes "interesting" steering and control characteristics when used as part of the steer axle that system wasn't used in regular passenger cars.

Rodger

I wonder how it works in the manual cars. I got stuck in the snow pretty good a few years back. It was in my driveway. I had already switched my wheels over and then we got a snow storm in late April. I made it all the way home and then got stuck in the driveway. With TCS on I was feathering the accelerator and didn't have the clutch pedal depressed at all. Wheels didn't spin at all because of TCS, but the engine didn't die, either.

 

[rsingl]

The TCS can apply light braking to one of the driven axle wheels regardless of transmission type.

But something was spinning or slipping with your 2.0T manual equipped ATS because the power generated in the engine had to be going somewhere.

With an open differential, if a wheel has no traction (worst case would be one wheel out of contact due to high centering on the snow) then almost no torque would make it to the wheel with traction and the free wheel would spin vary rapidly.

An old trick used by many of us was to LIGHTLY apply the manual parking brake in this situation and along with judicious feathering of the throttle, you could often get moving. The parking brake provided enough drag to the spinning wheel that sufficient power was also applied to the side with traction to get the vehicle underway.

A limited slip or full locking differential will work even better in these very low traction situations but individually braking the spinning wheel works well enough for most situations and is effectively free since those systems are already available via ABS and stability control. Electronically controlled true LSD axles are even more capable since they become a key part of the active handling system but the expense and complexity of those is overkill for average consumer usage.

Rodger