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

[WalleyeMikeIII]

Can you please read this: https://www.linkedin.com/pulse/what-sprung-unsprung-weight-nikhil-jagdale#:~:text=Sprung weight includes anything supported,you're considering making modifications.

If OP would respond back we may get a better idea of what's happening. Probably a combination of things.

Read it...understand it (engineer here). Agree with all of it.

 

[steiny93]

It's basic physics. Heres a quick simple read to help you over come your lack of understanding.
https://www.linkedin.com/pulse/what-sprung-unsprung-weight-nikhil-jagdale#:~:text=Sprung weight includes anything supported,you're considering making modifications.

Big brakes will negatively affect mpg. OP is having a drastic reduction which could be a combination of factors. But to dismiss the rotational mass all together is short sighted.

The point is that the difference in the weight is small, IE it isn't enough to cause this significant (6-8mpg) of an impact of mileage to occur.

Many of us know this as we have had these same vehicles with both brake kits on them and our mileage wasn't impacted to this degree. Adding the GMC Brembo kit will not impact mileage by 6-8mpg because of the weight difference.

Additionally the weight difference of this kit is less then the typical weight difference when folks change tires.

 

[Tahoered]

Hey Guys. Just checking up on the responses and appreciate all of the info being exchanged here. I truly do. Appointment updated for this coming Monday. I want to get there early and have an experienced tech for a thorough test drive. I understand the weight debate...in younger years I seemed to have always installed larger rims which were always heavier than stock, however, this is significantly different. I haven't towed anything with the Taboe yet but I've driven miles with the cabin full of luggage and family and it does not compare to this. I mean, truthfully, you cant even feel the difference in dryiving dynamics from when empty versus driving with 7 or 8 people with luggage in this Tahoe. It just effortlessly gets moving. I am stumped that I am not getting any clear indication of heat coming from any of the rotors or a scent. I wish that were the case. Mind you, the weight added on the vehicle I owned when younger were simple sedans with hp ratings of 190 (95 Maxima) to 250 (08 Maxima). We are now talking about a 6.2L 420 hp engine. It's somewhat hard to believe the rotors and calipers would make that much of a difference. My rear drivers side rotor is showing grooves all around. I've only placed roughly 120 miles since getting these things installed. Other 3 rotors look fine. As reference, this gives me the exact feel one would get if driving a car and the hand brake was lifted. Extra pressure on gas pedal to get moving. Heavier or more weighted steering. Even cruising (letting go of gas pedal) clearly slows down faster than before. I'll be sure to update the chat Monday evening. Really appreciate each and every one of you. Thanks guys.

 

[Rocket Man]

It's basic physics. Heres a quick simple read to help you over come your lack of understanding.
https://www.linkedin.com/pulse/what-sprung-unsprung-weight-nikhil-jagdale#:~:text=Sprung weight includes anything supported,you're considering making modifications.

Big brakes will negatively affect mpg. OP is having a drastic reduction which could be a combination of factors. But to dismiss the rotational mass all together is short sighted.

I said by 6-8 mpg, it’s not happening. No need to be rude. I understand you think you’re smart. These vehicles weigh so much that the slight bit of added rotational mass ( rotors) isn’t going to amount to anything that will affect mpg except slightly, probably not even enough to notice. The slanty pedal will, as noted by other sensible members here. And you’re not really adding anything noticeable in unsprung weight ( calipers) because there’s what, maybe 10 lbs difference? That’s like throwing a few tools in the back. If you still think either of these changes are going to make more than .5 mpg difference in a 5500 lb vehicle with 300 hp you’re out of your mind. Your common sense is missing. This isn’t a race car where every pound counts. We aren’t talking about seconds in a quarter mile. We aren’t dealing with a tiny car that gets 45 mpg.

 

[66 Galaxie]

Based on your description of rotor condition the left rear sounds like the problem. Could be parking brake, sticking pistons in caliper or a brake line that was “kinked” during installation so it delays the release of brake fluid pressure which will cause temporary dragging of the caliper. After sitting for enough time the caliper will release until the next time you use the brakes then it will cause a temporary dragging brake again.

 

[DuraYuk]

I said by 6-8 mpg, it’s not happening. No need to be rude. I understand you think you’re smart. These vehicles weigh so much that the slight bit of added rotational mass ( rotors) isn’t going to amount to anything that will affect mpg except slightly, probably not even enough to notice. The slanty pedal will, as noted by other sensible members here. And you’re not really adding anything noticeable in unsprung weight ( calipers) because there’s what, maybe 10 lbs difference? That’s like throwing a few tools in the back. If you still think either of these changes are going to make more than .5 mpg difference in a 5500 lb vehicle with 300 hp you’re out of your mind. Your common sense is missing. This isn’t a race car where every pound counts. We aren’t talking about seconds in a quarter mile. We aren’t dealing with a tiny car that gets 45 mpg.

No one is being rude. We are talking about something that can lead to mpg decrease. You have missed the point completely. The link was for you to understand. Weight does make a big difference doesn't matter how big or small the vehicle is. Sounds like his e brake is dragging. Either way we are here to help OP and throwing out sane logic won't help him.

 

[Rocket Man]

No one is being rude. We are talking about something that can lead to mpg decrease. You have missed the point completely. The link was for you to understand. Weight does make a big difference doesn't matter how big or small the vehicle is. Sounds like his e brake is dragging. Either way we are here to help OP and throwing out sane logic won't help him.

I think it’s you who have missed the point completely. I stated adding a BBK to one of these heavy SUV’s won’t affect your gas mileage enough to notice, certainly not like the OP questioned in his original post. In case you missed it, in his first post as well as in post #16 he’s considering going back to his original brakes because he’s thinking the added weight of this kit has not only decreased his mpg from 18-19 to 12 but he’s even running his tires at 42psi in order to decrease his rolling resistance. And not only is the truck down 6-7 mpg but in his words it feels like he’s pulling a trailer. I’m trying to let him know that adding a BBK to these isn't going to do that. It has to be something else. And I have added Wilwood 16” front/ 14” rear kits on both my 02 supercharged/ cammed Yukon Denali as well as my 08 bagged Silverado with a cammed 4.8 and on neither one did I see any noticeable change in my mileage. Not even 1 mpg, so I might understand more than you think. There are others here who have added BBK’s and none have seen a drop in mileage. I’m done with this little game of I’m right, you’re wrong shit. I’m also trying to help the op, with my actual real world experience. It’s you who aren’t helping with the talk of rotational mass and unsprung weight bs. Show me an instance of a full size GM SUV that has seen a decrease in their mileague from installing a BBK. Actually, no don’t show me at all. Show the OP. Otherwise you’re just blowing smoke up someones ass.

 

[Doubeleive]

No one is being rude. We are talking about something that can lead to mpg decrease. You have missed the point completely. The link was for you to understand. Weight does make a big difference doesn't matter how big or small the vehicle is. Sounds like his e brake is dragging. Either way we are here to help OP and throwing out sane logic won't help him.

it's just not going to happen with these vehicles. period you can throw math at it all day. meanwhile I can load it up with a 1000lbs of metal and get the same mpg i did empty. it wont handle the same but it will get basically the same mpg on level ground provided you go easy on the pedal.

 

[DuraYuk]

I think it’s you who have missed the point completely. I stated adding a BBK to one of these heavy SUV’s won’t affect your gas mileage enough to notice, certainly not like the OP questioned in his original post. In case you missed it, in his first post as well as in post #16 he’s considering going back to his original brakes because he’s thinking the added weight of this kit has not only decreased his mpg from 18-19 to 12 but he’s even running his tires at 42psi in order to decrease his rolling resistance. And not only is the truck down 6-7 mpg but in his words it feels like he’s pulling a trailer. I’m trying to let him know that adding a BBK to these isn't going to do that. It has to be something else. And I have added Wilwood 16” front/ 14” rear kits on both my 02 supercharged/ cammed Yukon Denali as well as my 08 bagged Silverado with a cammed 4.8 and on neither one did I see any noticeable change in my mileage. Not even 1 mpg, so I might understand more than you think. There are others here who have added BBK’s and none have seen a drop in mileage. I’m done with this little game of I’m right, you’re wrong shit. I’m also trying to help the op, with my actual real world experience. It’s you who aren’t helping with the talk of rotational mass and unsprung weight bs. Show me an instance of a full size GM SUV that has seen a decrease in their mileague from installing a BBK. Actually, no don’t show me at all. Show the OP. Otherwise you’re just blowing smoke up someones ass.

No one is blowing smoke. I showed you the link that goes in detail what rotational mass can do. It may not be a result of his total 8mpg decrease but it is no doubt attributing to it. Especially if he is pressing the gas more to overcome the heavier feel. Im willing to bet the truck feels 'heavier' to him and he is using the gas to compensate.

Rotational mass increase can make a vehicle feel very labored. Some less sensitive may not feel it. But many people will.

It could be a dragging brake but he mentions no heat. A single caliper dragging will also cause a pull. What's the likelie hood of a pair dragging ? Probably pretty slim. So next up would be a e brake dragging. Again he says no heat. So that may or may not be it. He doesn't mention any pulling so that rules out a single corner.

The one fact we do have is that he put giant brakes on his suv and complains that it is labored and struggling and low mpg.

To rule out what im saying as 'smoke' is ignorant.

 

[DuraYuk]

it's just not going to happen with these vehicles. period you can throw math at it all day. meanwhile I can load it up with a 1000lbs of metal and get the same mpg i did empty. it wont handle the same but it will get basically the same mpg on level ground provided you go easy on the pedal.

Yes, sprung vs unsprung weight. Rotational vs static. https://www.linkedin.com/pulse/what...orted,you're considering making modifications

It will be interesting to see what it ends up being. Hopefully he replies back with a quick fix.