Gm Brembo upgrade added...sluggish acceleration and much lower mpg.

[Tahoered]

Hi guys. Need some advice. A couple of weeks ago I added the GM - Brembo big brake kit on my 2022 RST 6.2. I only drive the vehicle in weekends and have placed roughly 100 miles on it since adding the brake package. Problem is, I can clearly sense a difference with drivability. I understand the larger rotors may weigh more and possibly even the larger caliper but My G-D!! My mpg is now at 12!!! My acceleration seems labored as if I am towing something. Never have I felt this in a car. Even the acceleration sound driving normally seems as if my engine is working harder. I ultimately went back to the dealer where it was installed. They placed it on lifts and stated they see nothing wrong because the wheels / rotors are spinning freely. After driving for an additional 30 miles with mpg plunging to 11, I have made an appointment and will not accept any other excuses from them. Not sure what the tech may have done. Dragging calipers, brakes not fully releasing? Is it possible he may have tightened something too much where my ebrake is slightly holding or something. Any ideas or thoughts would be greatly appreciated. My steering feels heavy also and it just seems as if more weight has been added. Really thinking of removing these things and getting my lively RST back to stock.

 

[swathdiver]

That doesn't seem right to me either. If the current dealership can't get the job done right, you can certainly take it to another one.

When stuff like this has happened to me, I bypass the service writers and slip around back and get with the mechanics and find the right man for the job.

 

[RedInCo]

This is a good case for using a remote-reading infrared thermometer. You can drive a bit and then measure how hot your rotors and hubs are.

The one I have came from Radio Shack and is about 15 years old. Sorry I can't recommend any particular current one. Here is one example: https://www.summitracing.com/parts/wmr-w89722

 

[Doubeleive]

I would have doubts about it being brake related, probably something else
have you been driving it harder since the brake upgrade?

 

[Tahoered]

I would have doubts about it being brake related, probably something else
have you been driving it harder since the brake upgrade?

Not at all. Used as the highway cruiser / highway family hauler for trips.

 

[Doubeleive]

Not at all. Used as the highway cruiser / highway family hauler for trips.

lot of members here have upgraded there brakes in various ways including myself and have zero effect on mpg, even if the brakes were dragging a little bit you most likely wouldn't even feel it. It's probably just coincidence especially if you can spin the wheels easily by hand.
I am not saying it's impossible you could bring your concerns to the "service manager" and ask to have it double checked with more than just spinning the wheels, at the same time tell them you have experienced a noticeable drop in mpg and ask to have it checked with a scanner.

 

[DuraYuk]

You increased the rotational weight. I wonder how much more each rotor weighs compared to stock. Even 1 pound per corner would be huge.

I'd disconnect the battery for a bit and reset and drive and see how your mpgs do.

What was it previously ? Sometimes crappy gas cab do it too.

Don't always assume the job was done incorrectly. Pretty hard to mess up this upgrade. Could just be a coincidence.

 

[mb1500]

This is getting a little out there. OP is not driving a Miata on the autocross track, he is cruising down the highway with his family in a 5,500 pound SUV with over 400 horsepower. The additional weight is completely irrelevant to the problems that the OP is having.

Something is not right with the vehicle, which may or may not be related to the recent work that had been done. Needs to be sorted by a knowledgeable mechanic...

 

[Holy Roller]

You increased the rotational weight. I wonder how much more each rotor weighs compared to stock. Even 1 pound per corner would be huge.

I'd disconnect the battery for a bit and reset and drive and see how your mpgs do.

What was it previously ? Sometimes crappy gas cab do it too.

Don't always assume the job was done incorrectly. Pretty hard to mess up this upgrade. Could just be a coincidence.

I agree. Increased rotational mass was the first thing that I thought of.

 

[Doubeleive]

B.S. i added Baer erradispeed brakes to all 4 corners of mine those are way more than a lb extra each, did not change even a fraction of mpg, neither does adding 500+ lbs of people and gear. what does change it? pushing the big pedal.