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As everyone knows, ZZP is coming out with a rotor/caliper kit for our car; however, ECO and LS owners have drum brakes on their rear axles and therefore need some sort of conversion kit.

Now, I went to my dealership today to ask a couple questions, and here are the answers;

Cruze models with drum brakes have either a GNG or GNC rear axle.

ONLY Cruze models with the GNG axle can directly bolt on disc brakes to their rear wheels[In order to figure out what axle you have, all you need is to give your VIN to your dealer].

In order for a complete conversion, you have to replace the elastic brakes lines that run from the axle to the brake, as well as replacing a monitor/pump in the ABS system. The reason for replacing the pump is simply due to disc brakes needing more fluid to push the piston in the caliper compared to the piston in the drum brakes.


So, for those who want the ZZP Rotor/Caliper upgrade, you have to have a GNG rear axle, and 1-3 replacement parts will need to be purchased for a full conversion.
 

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i see a lot guys wanting to dump the rear drums. i suspect the reason gm did the drums was for mileage. i do a lot of drag racing and have always been told the drums will completely release and have no friction compared to the disk which will mostly release but still have a little drag on them since there is no springs to pull the pads back. just something to think about.
 

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The drum brakes on my 2LT are huge IMO. I think the car has excellent brakes...I've had idiots (2) pull out directly in front of me in the last month and the car has surprised me, stopping so quickly and true. I was looking to switch them out until I had to really use the brakes hard. I figured I'd save my cash and the P.I.T.A. of swapping them out. I don't really like the look of them though.
 

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Discussion Starter · #6 ·
Having to have slam on my brakes 4 times already, I know the stopping power the drums provide, and I can assume that two people can go on for days fighting over whether or not drums are better than disc brakes. The point of this thread is to simply give information to those who want disc brakes instead of drums.

Not everyone will be drag racing their Cruze. Its an economy car, so you can bet that drag racing performance isn't on everyone's list. Most people want the look, and if disc brakes aren't terrible compared to drums, and someone wants to pay the extra for a nice look; whos to say they're stupid for spending their own money on their own car?
 

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My experience is that drums dry quicker in the rain which translates to a slightly quicker grab in a wet emergency stop. The water is thrown directly off the drum vs having to run to the edge of a disc brake.
 

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i see a lot guys wanting to dump the rear drums. i suspect the reason gm did the drums was for mileage. i do a lot of drag racing and have always been told the drums will completely release and have no friction compared to the disk which will mostly release but still have a little drag on them since there is no springs to pull the pads back. just something to think about.

The reason is for cost factor. A parking brake set up on disc brakes is as complex as drum brakes themselves. Disc brakes do release, and the minor friction caused by how they ride wouldn't drag the vehicle at all.
 

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Having to have slam on my brakes 4 times already, I know the stopping power the drums provide, and I can assume that two people can go on for days fighting over whether or not drums are better than disc brakes. The point of this thread is to simply give information to those who want disc brakes instead of drums.

Not everyone will be drag racing their Cruze. Its an economy car, so you can bet that drag racing performance isn't on everyone's list. Most people want the look, and if disc brakes aren't terrible compared to drums, and someone wants to pay the extra for a nice look; whos to say they're stupid for spending their own money on their own car?
i never said anyone was stupid. just posting up a reason why gm may have thought drums were a good idea on this car. my post may have mentioned drag racing but it was meant to bring up the slight extra drag of the disc brakes and infer that it may effect your mileage. i am sure it is a slight difference but like most of the changes on the eco they are all slight and add up to something significant. after doing a search on the subject i am finding a number of references saying that drum brakes do likely have less resistance than disc.

Disc brakes rely on pliability of caliper seals and slight runout to release pads, leading to drag, fuel mileage loss, and disc scoring. Drum brake return springs give more positive action and, adjusted correctly, often have less drag when released.
 

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My wifes LTZ had rear discs and I like the way the braking bias is setup. Its alot like my G35 was in that when braking hard the car doesnt nosedive. Thats the way brakes are supposed to work IMO. Having most braking power on the front wheels tends to throw you thru the windshield when braking hard.
 

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As everyone knows, ZZP is coming out with a rotor/caliper kit for our car; however, ECO and LS owners have drum brakes on their rear axles and therefore need some sort of conversion kit.

Now, I went to my dealership today to ask a couple questions, and here are the answers;

Cruze models with drum brakes have either a GNG or GNC rear axle.

ONLY Cruze models with the GNG axle can directly bolt on disc brakes to their rear wheels[In order to figure out what axle you have, all you need is to give your VIN to your dealer].

In order for a complete conversion, you have to replace the elastic brakes lines that run from the axle to the brake, as well as replacing a monitor/pump in the ABS system. The reason for replacing the pump is simply due to disc brakes needing more fluid to push the piston in the caliper compared to the piston in the drum brakes.


So, for those who want the ZZP Rotor/Caliper upgrade, you have to have a GNG rear axle, and 1-3 replacement parts will need to be purchased for a full conversion.
Well since you took the initiative, it is only fair to say you have to be the first to do it and document every step of the way.
 

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The drum brakes on my 2LT are huge IMO. I think the car has excellent brakes...I've had idiots (2) pull out directly in front of me in the last month and the car has surprised me, stopping so quickly and true. I was looking to switch them out until I had to really use the brakes hard. I figured I'd save my cash and the P.I.T.A. of swapping them out. I don't really like the look of them though.
The reason our stock brakes suck and people want to upgrade is not because they aren't up to task for quick safe stops in the manor you just mentioned....

The problem with our brakes will be seen when you experience a series of repeated hard braking or in high speed braking, these situations will heat the brakes to the point where you will experience brake fade. Brake fade is when the brakes become so hot that coefficient of friction is lost and the brakes simply do not perform nearly as well as they did at lower temps.

Solutions are bigger rotors that can absorb more heat before brake fade occurs, bigger multi-piston calipers that have a better clamping force and performance brake pads that are made up of compounds that provide more friction to the rotors.
 

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These cars along with most any new car have EBD (Electronic Brakeforce Distribution), so none of them should nosedive seriously. It allows an initially very high pressure to be pushed to the rear brakes, then opens the valves in the Stabilitrack (ESP) module to reduce the pressure to keep them from locking. It can adjust this dynamically.

Also, I don't think you will need to change the ESP module. If anything is different, its just the programming. They may be a different part number JUST for this. The fluid volume consumption is likely not vastly different between the disk and drum brakes in the back. If they were, the master cylinder would likely be very different. This is not like converting a 1960's car from front drum to front disk where there is a big difference.

With that being said, I would suggest just sticking with what you have. Likely the axles aren't actually different for caliper mounting...the difference is probably only with or without z-link.

drum brakes will have more initial bite than the rear disk brakes, then fade more quickly. the back of this car is pretty light. Your best bet on performance for the dollar is to put larger front rotors on the car and pads with higher friction coefficients. I'd be interested to see if the Verano or Volt uses larger rotors. If that was the case it would be a cheap rotor/bracket upgrade.
 

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Discussion Starter · #16 ·
Well since you took the initiative, it is only fair to say you have to be the first to do it and document every step of the way.
Alas, I don't have the money. If I did, This thread would be a look at my actual conversion, instead of here's what I've been told if you want to do it ;)
 
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My experience is that drums dry quicker in the rain which translates to a slightly quicker grab in a wet emergency stop. The water is thrown directly off the drum vs having to run to the edge of a disc brake.
I have found the opposite to be true, especially if driving through deep water. The drum collects and holds water inside until it can drain out. With the disk the water is not collected at all. I've needed to drive up to half mile after getting out of deep water before the drum brakes become fully functional again.

As far as drag goes, yes the disk pads do float on the surface. But they will fully release within a short distance. If they did not, then the components would rapidly heat up and fail.
 

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My wifes LTZ had rear discs and I like the way the braking bias is setup. Its alot like my G35 was in that when braking hard the car doesnt nosedive. Thats the way brakes are supposed to work IMO. Having most braking power on the front wheels tends to throw you thru the windshield when braking hard.
I have a feeling a car's ability to nosedive isn't going to be determined by the strength of the rear brakes or the brake bias. I would imagine that has more to do with the weight distribution and suspension.

The reason our stock brakes suck and people want to upgrade is not because they aren't up to task for quick safe stops in the manor you just mentioned....

The problem with our brakes will be seen when you experience a series of repeated hard braking or in high speed braking, these situations will heat the brakes to the point where you will experience brake fade. Brake fade is when the brakes become so hot that coefficient of friction is lost and the brakes simply do not perform nearly as well as they did at lower temps.

Solutions are bigger rotors that can absorb more heat before brake fade occurs, bigger multi-piston calipers that have a better clamping force and performance brake pads that are made up of compounds that provide more friction to the rotors.
I'd like to present a few thoughts for discussion purposes. I read in a comedic article related to cars that if you need to make multiple repeated stops during day to day driving, you have a problem bigger than your brakes. Either that problem is a bunch of idiots who pull out in front of you one after another, or you're following too closely. However, having driven my Eco for a while and having had to make a few hard stops, I can't really see much of a problem with the braking capacity of the car on one, maybe two emergency stopping maneuvers. It's not a sports car after all.

That said, I question the need for something bigger on the rear of the car. With our front-heavy weight distribution, how much braking does the back actually do? I don't know the exact percentage off the top of my head, but I'd guess it's somewhere around 80/20 front/rear. Sounds to me like any benefit to the rear brakes is going to be rather minor if you're looking for better emergency braking. As you mentioned, bigger rotors, better pads, bigger calipers, etc. I've personally experienced improvements in stopping distance from simple "premium/high performance" brake pad upgrades, although not all "high end" brake pads are created equal.
 

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I have found the opposite to be true, especially if driving through deep water. The drum collects and holds water inside until it can drain out. With the disk the water is not collected at all. I've needed to drive up to half mile after getting out of deep water before the drum brakes become fully functional again.

As far as drag goes, yes the disk pads do float on the surface. But they will fully release within a short distance. If they did not, then the components would rapidly heat up and fail.
I wouldn't say they'd rapidly heat up and fail. It's not like you have a stuck caliper that's dragging, but it would be enough to cause a bit of pull. It won't make a huge difference, but you'll have some drag nonetheless. I think GM went for the "every last effort" approach to getting better fuel economy, and as many have proven with the Cruze Eco, it paid off.
 

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Not to revive an old thread. I have been considering giving this a try for a while. Anyone know if Id have to switch the entire axle out, or are the rear spindles the same?
 
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