[Stormbreaker]

Hello Everyone!

I recently picked up a 2016 Challenger Hellcat and noticed that the front rotors look like the bottom pic.They have very limited slots and did not know if that is supposed to be like that or are they worn. Any help is appreciated!

 

[Slidd]

The factory original 2016 rotors had multiple slots but the later rotors almost have none. I'm guessing yours are the service replacements that have the fewer slots. Don't know the reason why they reduced the number but all the new 6-piston cars in the last few years are like this.

As a double check, if you can measure the rotor thickness, new they were 34.00 mm thick.


Sent from my SM-N960U using Tapatalk

 

[Stormbreaker]

Thank you for the help!!! Very appreciated! I was about to invest in some new ones 😅 which I know aren’t cheap!

 

[Blickie]

Hello Everyone!

I recently picked up a 2016 Challenger Hellcat and noticed that the front rotors look like the bottom pic.They have very limited slots and did not know if that is supposed to be like that or are they worn. Any help is appreciated! View attachment 602677

You stated that both fronts match the pic... that means they are matched and have the same # of slots in the same position, inner and outer... that's good and best.

The number and position of the slots have changed over the years. Yours have less than some predecessors which is fine. There has always been a discussion as to what the slots actually do and do we need them.

Slots are designed to wipe away spent friction from the brake pads surface exposing new friction material for better stopping performance. Not sure they have any real value unless you track the car. Also, many have called the slots "cheese graders" to the brake pads and wears the pads out quicker. It would seem whoever designed your rotors wanted the best of both worlds keeping the slots while reducing the total number.

I doubt you'll notice any brake performance issues, one way or the other, at all.

 

[Speedlogix Sales]

The Demon performance rotors are great and have more slots than the newer style OEM rotors!

- Alexis

 

[ArchGE]

Congrats on the new ride and welcome from Colorado!

 

[why2kmax]

didnt the reduction in slots start when California banned copper in the brake pad lining and the pads got a bit bigger?

 

[Bobo]

didnt the reduction in slots start when California banned copper in the brake pad lining and the pads got a bit bigger?

I have no clue as I'm new to my Challenger but I would tend to say yes because....California screws up everything good!

 

[Slidd]

didnt the reduction in slots start when California banned copper in the brake pad lining and the pads got a bit bigger?

I think it started before that, like maybe 18 or 19.

Didn't know the pads were bigger but the rotors definitely got bigger (15.7" vs 15.4") in 2021.


Sent from my SM-N960U using Tapatalk

 

[Sarna March]

You stated that both fronts match the pic... that means they are matched and have the same # of slots in the same position, inner and outer... that's good and best.

The number and position of the slots have changed over the years. Yours have less than some predecessors which is fine. There has always been a discussion as to what the slots actually do and do we need them.

Slots are designed to wipe away spent friction from the brake pads surface exposing new friction material for better stopping performance. Not sure they have any real value unless you track the car. Also, many have called the slots "cheese graders" to the brake pads and wears the pads out quicker. It would seem whoever designed your rotors wanted the best of both worlds keeping the slots while reducing the total number.

I doubt you'll notice any brake performance issues, one way or the other, at all.

Holes or slots in brake rotors do not shave off parts of the brake pads.

Holes that go all the way through allow the escape of gasified material and any vaporized water. Racing teams use or used them for decades. They increase both pad and rotor life in situations where extremely hot brake and pad temperatures are consistently encountered.

Some brake shops claiming they "can't surface any them thar brake rotors cuz them gots slots that flat bust the machine" have struck me as quite odd. The surfacing bit does not "ride" on the surface of the rotor, then "fall" into the hole or slot as it passes by. It is set at a depth and it goes to that position/depth only, to my knowledge.

 

[AeroF16]

Holes or slots in brake rotors do not shave off parts of the brake pads.

Holes that go all the way through allow the escape of gasified material and any vaporized water. Racing teams use or used them for decades. They increase both pad and rotor life in situations where extremely hot brake and pad temperatures are consistently encountered.

Some brake shops claiming they "can't surface any them thar brake rotors cuz them gots slots that flat bust the machine" have struck me as quite odd. The surfacing bit does not "ride" on the surface of the rotor, then "fall" into the hole or slot as it passes by. It is set at a depth and it goes to that position/depth only, to my knowledge.

Those bits are very expensive and shops that don’t want to turn rotors like that have probably broken a few and just don’t want to deal with it.

Maybe setting the lathe speed too fast or depth too deep? I don’t know, I think it’s definitely a skill/experience thing and the local O’reilys may not have the talent to do it without going through $10k in bits haha.

 

[Bobo]

Holes or slots in brake rotors do not shave off parts of the brake pads.

Holes that go all the way through allow the escape of gasified material and any vaporized water. Racing teams use or used them for decades. They increase both pad and rotor life in situations where extremely hot brake and pad temperatures are consistently encountered.

Some brake shops claiming they "can't surface any them thar brake rotors cuz them gots slots that flat bust the machine" have struck me as quite odd. The surfacing bit does not "ride" on the surface of the rotor, then "fall" into the hole or slot as it passes by. It is set at a depth and it goes to that position/depth only, to my knowledge.

Those bits are very expensive and shops that don’t want to turn rotors like that have probably broken a few and just don’t want to deal with it.

Maybe setting the lathe speed too fast or depth too deep? I don’t know, I think it’s definitely a skill/experience thing and the local O’reilys may not have the talent to do it without going through $10k in bits haha.

It’s the interrupted cut that breaks the bits. As a journeyman machinist for the last 25 years or so and having done my fair share of lathe work, I hate interrupted cuts on a lathe. It causes tool breakage, crappy cut patterns and a whole slew of other issues.
No doubt you can do it but it’s a pain in the azz to get a smooth FLAT surface that would be an acceptable breaking surface.
The biggest issue is getting a smooth flat cut, each time the cutter drops into a slot it “clunks” against the wall of the other side and gouges deeper and then back out to the set depth. So you end up with a wavy surface. You might not see it or feel it but if you measured it with gages there would definitely be high and low spots in a pattern pertaining to the slots.
The only way to make sure it’s smooth and FLAT is many many micro passes and most shops don’t want to deal with the time it would take to get the needed flatness.

My only benefit is as a machinist I can just take mine to work with me and do them myself. Take as much time as needed to make them right plus I have to correct inserts to do the interrupted cuts .002” at a time on CNC equipment😊 I just set it up and let it run, so if it takes an hour so be it. I can do something else while it just does it’s thing.

 

[SickToo]

I second the slots are there for gasses. What does the manufacture do, use some high dollar grinder sorta like what surfaces a flywheel? Or are the slots machined into the rotor after it’s surfaced? Never thought about that part of it before

 

[Bobo]

I second the slots are there for gasses. What does the manufacture do, use some high dollar grinder sorta like what surfaces a flywheel? Or are the slots machined into the rotor after it’s surfaced? Never thought about that part of it before

The machining process I know that Stellantis does for the torque converters (I used to work in that plant)
I would say they machine the slots AFTER the surfaces are finished. They are going to avoid the interrupted cuts also, Breaking inserts constantly is expensive.

 

[Sarna March]

It’s the interrupted cut that breaks the bits. As a journeyman machinist for the last 25 years or so and having done my fair share of lathe work, I hate interrupted cuts on a lathe. It causes tool breakage, crappy cut patterns and a whole slew of other issues.

However, when I see, for example, cylinder heads being flattened on their faces, the tool approaches the cylinder head from the side on each rotation and doesn't instantly shatter, scattering lethal shards everywhere. Every time the bit passes over a combustion chamber or bolt or water or oil hole, it is yet another interrupted cut. No cloud of razor-sharp, sonic-speed tool bit fragments.

The same thing with cylinder blocks being decked. Somehow, no deaths or tool shattering.

What is odd is that "interrupted cuts" have been done for decades, if not centuries, and yet they only seem to be an issue when the opportunity to sell someone new rotors instead of having to spend the time to resurface the old ones arises.

Here is a video demonstrating someone resurfacing a brake rotor without everything everywhere shattering into pieces. Take careful note of the myriad of holes in the surface of the brake rotor.

Here's another one by Powerstop:

And a drilled rotor from a race car:

As you can see, if someone says the slotted or drilled rotors can't be resurfaced, they are patently, obviously, completely, and obviously wrong.

 

[Sarna March]

So, this is what I glean from this situation:

"Though I make more money faster by telling you no drilled or slotted brake rotor, can be resurfaced, you should trust ME, not the facts proving me completely wrong."

 

[Bobo]

However, when I see, for example, cylinder heads being flattened on their faces, the tool approaches the cylinder head from the side on each rotation and doesn't instantly shatter, scattering lethal shards everywhere. Every time the bit passes over a combustion chamber or bolt or water or oil hole, it is yet another interrupted cut. No cloud of razor-sharp, sonic-speed tool bit fragments.

The same thing with cylinder blocks being decked. Somehow, no deaths or tool shattering.

What is odd is that "interrupted cuts" have been done for decades, if not centuries, and yet they only seem to be an issue when the opportunity to sell someone new rotors instead of having to spend the time to resurface the old ones arises.

Here is a video demonstrating someone resurfacing a brake rotor without everything everywhere shattering into pieces. Take careful note of the myriad of holes in the surface of the brake rotor.

Here's another one by Powerstop:

And a drilled rotor from a race car:

As you can see, if someone says the slotted or drilled rotors can't be resurfaced, they are patently, obviously, completely, and obviously wrong.

Ummm, who said it couldn’t be done??? I’ve been doing it for year, it’s just a pia. Like I said in another post I would take mine to work and just do them myself.
In reference to your shattered shards of planet destroying fragments flying through the air killing the entire population of Utah?! No one said that or even implied that. As far as cylinder heads and decking blocks, completely different process with different feeds, speeds and tools. Surface speed and chip load are everything.
I’m guessing you know that though.
Plus having a flat surface with a mailable gasket between seal when they don’t move except for heat expansion (press sure puts vertical stress not side load pressure) is WAY different than a high friction surface being squeezed from both sides under extreme pressure, just a tad different situation! Hey if you don’t mind pulsation in your brakes then no problem. I guarantee the new kid at the auto parts store is gonna fu€k up your rotors or break a tool, take them to an actual machine shop and they will do them no problem. It’s still a pia!!
But…I’m guessing you know that to.

 

[Sarna March]

who said it couldn’t be done???

It’s the interrupted cut that breaks the bits.

Those bits are very expensive and shops that don’t want to turn rotors like that have probably broken a few and just don’t want to deal with it.

They are going to avoid the interrupted cuts also, Breaking inserts constantly is expensive.

 

[Bobo]

Nice again nobody said it can’t be done just that it’s a pia!!
You posted videos from Powerstop, Mercedes and a race car shop??? NOT your local neighborhood auto shop, big difference! Whatever it doesn’t matter, because you already know that.
Other than finding YouTube videos can I ask what your machining experience is?

 

[Sarna March]

Other than posting videos of people who do this for a living proving that it can easily be done, what experience do I need? I don't see how that is relevant. I am good at finding relevant facts, obviously.

It can easily be done by people who know what they're doing. I never indicated or implied these brake shops that claim The Apocalypse will occur if they DARE touch a slotted or perforated rotor are competent OR honest. If you are contending that the average shop has people either too lazy, greedy, or ignorant to be able to do that, that is another matter.