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2010 CTS4 3.6
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Discussion Starter #1
At 92,000km (65,00 miles), my CTS4 3.6 is going in for brakes next week. The dealer says that they replace rotors rather than machine them - to me that seems like a waste of money, and I told them I want them machined. What are your thoughts?
 

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2009 CTS4 Premium & 2012 SRX4 Luxury
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708 Posts
Resurface is a temporary fix. The thinner the material the shorter the time before they warp again. Unless you go with a very soft pad. My car had 67k when I bought it and the rotors have been replaced once and resurfaced twice. Next time it needs brakes I'm going J55 with aftermarket pads and rotors.
 

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CTS 2008 3.6DI Sport Luxury
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1,027 Posts
Resurface is a temporary fix. The thinner the material the shorter the time before they warp again. Unless you go with a very soft pad. My car had 67k when I bought it and the rotors have been replaced once and resurfaced twice. Next time it needs brakes I'm going J55 with aftermarket pads and rotors.
I agree. It will give you another 6-12 months and problem will come back, especially with hard pads.
 

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Cadillac CT6 (2019)
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2,306 Posts
There is a minimal thickness (for the rotor); if the rotors can be machined (resurfaced) and remain within specification (of thickness) then replacement is unwarranted in my opinion. And if the rotors are in fairly good condition (no gouges or other irregularities) sometimes just changing the pads is also adequate (especially if they were performing properly with the old pads and the old pads just wore out and ran out of friction material).
 

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2008 CTS Base Manual Tran
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553 Posts
Machining the rotors once would likely be fine. As long as the rotors are still within specified thickness...brake job should last as long as the new pads. Many believe that the concept of warped rotors is a myth...what people perceive as warping is really deposits form the brake pad bonding with the rotor. New rotor surface should be broke in properly with the new pads.
 

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2001 SLS & 2012 CTS
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58 Posts
Typically, many shops automatically replace rotors when doing new brakes. This prevents comebacks from "my brakes are pulsing" 2 weeks later.
Preventative maintenance for most shops.

Rotors do warp, I have seen them severely out of spec. Deposits/rust can give a temporary pulse, but It is not typically permanent.

As for machining, rotors are marked with minimum thickness to show how much they can be safely cut. Typically as you cut them, they then warp faster. It all depends on how you drive. If you are flying up & down hills & throwing it into turns. you may want the new rotors. If you mainly highway drive or are generally easy on the brakes, then cutting them should be fine.

My take is I change my own brakes & never resurface or replace rotors until & feel pulsation in the brakes. Some of my cars have not been cut for 3-4 sets of pads & are still fine. Money saved...
 

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2008 SRX V8AWD- 2012 CTS AWD Wagon-'17 CT6 3.0TT
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Resurface is a temporary fix. The thinner the material the shorter the time before they warp again. Unless you go with a very soft pad. My car had 67k when I bought it and the rotors have been replaced once and resurfaced twice. Next time it needs brakes I'm going J55 with aftermarket pads and rotors.
FYI
Brake rotors do not warp. Micro thin deposits form on them causing brake shudder. This is what people refer to as warping.
 

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2010 Black CTS 3.6L RWD , 2010 Silver CTS 3.6L RWD
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51 Posts
FYI
Brake rotors do not warp. Micro thin deposits form on them causing brake shudder. This is what people refer to as warping.
Are you kidding me!!!!
Why don't you go out and hold your brake partially on and drive around for a while and I assure you you will end up with a pulse and it wont be from your so called micro deposits. 2nd for the price of new rotors I wouldn't be doing any machining. 3rd the cost to have them done at a dealer is one of the reasons I call them stealerships. Go buy some nice new aftermarket pads and rotors for $100-200 and get a friend who will install them in 1hr flat and save yourself a ton of dough. Just make sure the sliders are still lubricated and the caliper still free floats. This is once of the easiest mechanical jobs to do on a car so surely you can find someone who has the knowledge and know how!!
 

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2001 SLS & 2012 CTS
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58 Posts
FYI
Brake rotors do not warp. Micro thin deposits form on them causing brake shudder. This is what people refer to as warping.
You are quoting BS with no actual experience. When you put a rotor on a brake lathe, it takes off metal to make it straight, not deposits.
Heat causes warpage, the rotor is no longer a consistent thickness pushing the pads away from the rotor... that is what you feel.
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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Think again "or ask any brake manufacturer". Cast iron does not warp. Yes, excess pad deposits can cause shudder/vibration, but when you see a rotor being machined it is metal being removed. However, this is NOT because the rotor has warped to an untrue state. Lateral run out is caused by uneven side to side wear of the friction surface. This is the inconsistent thickness you refer to. Warpage would cause the rotor to form into an (extremely subtle) zig zag shape, not vary thickness.

If heat/heating and cooling caused rotor warpage, every car on the planet would require extremely frequent rotor replacement. Especially after some not too uncommon circumstances - emergency braking, long descents, driving in rain, driving through a puddle.....

Race cars have been hearing iron rotors cherry red for many decades. They'd need rotor changes more often than tires. Do some research, this is old news, not some new crazy theory.

As for having rotors turned- If the old ones aren't excessively corroded, turning is a perfectly acceptable procedure. Sometimes, replacements are so cheap that it just makes more sense or is easier to replace them.

Some major brake parts manufacturers actually recommend having new rotors turned, on the cars hub, when new, to prevent future lateral runout.
 

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2001 SLS & 2012 CTS
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Your statement is generally correct except the statement that cast iron does not warp.... it does warp (or distort, whatever your preferred term) from excessive heat, or uneven cooling. It only takes riding the brakes for too long down a large hill to start the whole process. As you heat any metal, it expands. Due to the irregular shape of the rotor (hub etc. constraining equal expansion), it will change shape as it is heated. Once you reach critical temperature of the rotor (or a small portion of it) it can permanently change shape. The temperature it achieves will determine if the distortion will be permanent. This is why the heat sinking ability of the rotor is important... the thinner it is, the more likely it will overheat & permanently change shape.

The start of all brake pulsation is caused by uneven pressure between the pad & rotor... whether it be due to rotor warpage or runout starting the process. It causes (in simple terms) a high spot on the rotor. This area gets hotter than the surrounding area (due to pad friction), leading to hardening of the metal. The surrounding area is now softer & will wear faster. This leads to the problem that is the actual topic of conversation.
 

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08 CTS blk/blk
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I have had an ongoing problem with pulsing breaks. I have a long highway commute with heavy breaking. I will be going on my third brake job soon.

They pulse from "Hot Spots" on the rotor. This is created from differences in temperature on the surface and the actual change in molecular structure of the steel. I use only OEM pads and my most recent brake job I went with OEM rotors. I have to admit the OEM rotors are far superior to after market rotors. If you turn a rotor its only a temporary fix because the hot spot remains in the steel.

happy motoring
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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Your statement is generally correct except the statement that cast iron does not warp.... it does warp (or distort, whatever your preferred term) from excessive heat, or uneven cooling. It only takes riding the brakes for too long down a large hill to start the whole process. As you heat any metal, it expands. Due to the irregular shape of the rotor (hub etc. constraining equal expansion), it will change shape as it is heated. Once you reach critical temperature of the rotor (or a small portion of it) it can permanently change shape. The temperature it achieves will determine if the distortion will be permanent. This is why the heat sinking ability of the rotor is important... the thinner it is, the more likely it will overheat & permanently change shape.

The start of all brake pulsation is caused by uneven pressure between the pad & rotor... whether it be due to rotor warpage or runout starting the process. It causes (in simple terms) a high spot on the rotor. This area gets hotter than the surrounding area (due to pad friction), leading to hardening of the metal. The surrounding area is now softer & will wear faster. This leads to the problem that is the actual topic of conversation.
I know your mind is made up, but I'll again suggest getting your info from a brake parts manufacturer. They understand this better, and have more experience/R&D time in this than you or I ever will.
 

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They generally do not warp. This is an age old problem we experienced way back when we used brake drums; some of you may have heard of them.

The "hot spot" I referred to earlier is actually a hard spot as the result of uneven heating of the steel. The brake drum would actually imitate the same pulsing as do the rotors. The braking surface between the pad and the steel is not consistent and when the pad hits the hot spot it "speeds up" resulting in the pulse. All these CTS's should have had the larger rotors. This car is too heavy for the smaller rotors.

Happy Motoring!
 

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2010 CTS Sport Wagon 3.6
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Rotor warpage quite often a mis-dianosis. Pulsing brakes are generally caused by deposits on the rotor surface. The surface can be cleaned with a special abrasive pad that does not remove any metal.

Rotors should be machined if there is deep grooving on the surface preventing new pads from making full contact.
 

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Sold my 2009 CTS4 and my 2004 CTS
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If pulsing brakes had a simple solution, there wouldn't be so many different opinions and stories.
Personally, I believe that lateral run-out is the key contributor to pulsing brakes. The run-out causes the rotors to wear unevenly, which leads to variations in rotor thickness, which pulses your pedal.

I replace my rotors rather turn them. From personal experience, it is fairly unlikely that someone is going to be able to turn your rotors with any degree of quality. The only thing better than new rotors is to have them turned or ground while mounted on the wheel hub/bearing.

And here's something no one has mentioned... torqueing your lug nuts. Yep, I do that every time... in a cross pattern. I believe that uneven torque can also warp the rotor, which makes lateral run-out, which causes uneven wear, etc, etc.
Long gone are those days of hammering home the lug nuts with my impact. Ahhh, the memories.

My best brakes have always been the originals on a new car. They're never quite the same after that first brake job... or that first tire rotation.
Correct, I never rotate my tires until that first brake job, or the tires are wore out.

And that's why I never have pulsing brake pedals. Well, almost never. And maybe I'm just crazy.
 

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I've found the best place to get part numbers is acdelco.com. You have to use internet explorer though (at least it doesn't work with Chrome).

How much are people getting charged to turn rotors? I am in a somewhat remote area and the only place that will actually do it wants $25 per rotor. New rotors are only $45 at Amazon. Although I kinda like the idea of turning the old ones making them lighter.
 

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Sold my 2009 CTS4 and my 2004 CTS
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Make sure you get the right rotors and pads.
I just replaced my front pads yesterday, and got the wrong ones at first.
I have a base 2009 CTS with AWD, and apparently needed the longer pads.

I didn't get metal to metal, no pulsing, so the rotors are fine.
Apparently, there are two different size front rotors; 315 or 345mm. My rotors are about 12.5"' (315mm)
 
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