Interesting article from Hot Rod magazine in 2017.
Nutshelled : drilled/slotted rotors are akin to fake hood scoops. 

So why Corvette GS and Z06, GT350 and some other cars come with slotted and drilled brakes?

Edited June 19, 20196 yr by ykX

^ theoretically/possibly if the car is autocrossed heavily, I guess. Those above- at least that's a possibility.

All the 4-banger CUVs tho? Jest bling.

Ohh yea, unless the car is seeing track or autocross where heat dissipation is an issue , it is just for the bling and actually will hurt the braking distance (less friction surface)

That reminds me.. .I need to get a set of front rotors for the F-I-L's Cruze with the 1.8.... think I should get the cross drilled ones? 

30 minutes ago, Drew Dowdell said:

That reminds me.. .I need to get a set of front rotors for the F-I-L's Cruze with the 1.8.... think I should get the cross drilled ones? 

I would go for ceramic set

I will agree with @balthazar that most auto's this is bling, but high performance auto's and large SUVs like an escalade do benefit from a proper Brembo set of rotors and calipers. I have actually been thinking about upgrading the Escalade after I test drove a newer one at the dealership that had them and how much more stopping power you got on the bigger rotors and 8 piston calipers. It truly on a heavy auto makes a noticeable difference.

https://www.brembo.com/en/

Nice to see GM and Brembo have teamed up to offer an upgrade for the whole family of Suburban, Yukon, Escalade with bigger brake package / Performance.

https://www.brembo.com/en/company/news/brembo-and-gm-team-up-on-performance-front-brake-kit

Interesting to see the options of the upgrades from just pads, to rotors or complete brake systems offered from Tirerack.

https://www.tirerack.com/brakes/results.jsp?&autoMake=Cadillac&autoModel=Escalade+ESV+AWD&autoYear=2006&autoModClar=Platinum+Edition

Some auto's do look better with Bling!

Looks are one thing.  Performance is what matters.  Most trucks need those cross-drilled rotors as much as a typical Corvette. . . . . very badly.  Cadillac could stand to make those rotors standard across the entire line.

Rotor size & number of pistons is one (valid) thing. No trucks are seeing the level of hard usage that would require cross-drilling - of no benefit on street-driven vehicles.

12 minutes ago, balthazar said:

Rotor size & number of pistons is one (valid) thing. No trucks are seeing the level of hard usage that would require cross-drilling - of no benefit on street-driven vehicles.

Totally agree with you on the cross drilling as well as the rotor size and number of pistons. Interesting is that for the price, not many of the larger performance options come with just solid steel rotors compared to the cross drilled or slotted ones.

Still having the added stopping power on a full size SUV is nice.

8 minutes ago, dfelt said:

Interesting is that for the price, not many of the larger performance options come with just solid steel rotors compared to the cross drilled

What do rear spoilers do? Provide downforce?? Not on street cars, yet so many have them.

I don't think I've seen a 4-banger CUV with drilled and/or slotted rotors save for maybe things like a Mecan. 

[illustrative example]

On the flip side

 

Those brakes (both disc and pads) are not "blingy" enough (for the riciest version A-Spec)  and on top of all that...I find they are too small  as well(both disc and pads) for performance requisites...but I'm sure they do an adequate job of stopping.

 

Im OK with fake hood scoops and blingy, over the top, boy racer styling....if they compliment the look and feel of the car. If it the car (factory or custom) has a certain (boy) racer look about it, and mission,  and go-fast, bolt-on high performance parts are put unto the car and to compliment that look further, boy racer accessories are added...Im all for it!!!  

Edited June 19, 20196 yr by oldshurst442

1 hour ago, balthazar said:

What do rear spoilers do? Provide downforce?? Not on street cars, yet so many have them.

Your talking about this correct?

These actually have no affect on down force, but have a big affect on pushing air over the rear glass pushing off the water. I always thought they were a joke till I was in one watching it on a rainy day here in Seattle and surprised how much clearer that rear window stays with one.

See plenty on STI's

• The roof defusers have been there since the 60s on some station wagons; they're functional and not billed as being anything other than that. I was thinking more along the lines of any random decklid spoiler on any random family sedan, instead.

• I'm also fine with non-functional scoops (and cross-drilled rotors). Just don't think that I think your cross drilled rotors are providing you with any sort of braking performance improvement.

Edited June 19, 20196 yr by balthazar

1 hour ago, balthazar said:

• The roof defusers have been there since the 60s on some station wagons; they're functional and not billed as being anything other than that. I was thinking more along the lines of any random decklid spoiler on any random family sedan, instead.

• I'm also fine with non-functional scoops (and cross-drilled rotors). Just don't think that I think your cross drilled rotors are providing you with any sort of braking performance improvement.

I see and honestly cannot tell you other than it is the look that they put decklid spoilers on an Impala or any other sedan / coupe sold to Joe Public.

I also agree with you on the cross drilled part of the rotor for say my Escalade. I will say the much larger Rotor size and multiple piston brake system does make a big difference.

12 hours ago, dfelt said:

I see and honestly cannot tell you other than it is the look that they put decklid spoilers on an Impala or any other sedan / coupe sold to Joe Public. 

Cosmetic, I assume..to make otherwise bland appliances look "sporty".  Though there may be an aerodynamic advantage to some of them. 

Edited June 20, 20196 yr by Robert Hall

Ford put a rear wing on 2019 Mustang GT which is purely cosmetic, it is neutral aerodynamically.  That really pisses me off actually, I don't think it is that great looking and if you would do that, at least give it a little bit of functionality. 

21 minutes ago, Robert Hall said:

Cosmetic, I assume..to make otherwise bland appliances look "sporty".  Though there may be an aerodynamic advantage to some of them. 

Yes, some of them are for fuel economy rather than sportiness.  

18 minutes ago, ykX said:

Ford put a rear wing on 2019 Mustang GT which is purely cosmetic, it is neutral aerodynamically.  That really pisses me off actually, I don't think it is that great looking and if you would do that, at least give it a little bit of functionality. 

No different than having a factory wing on a 1999 Olds Alero

 Or  on a 442.

Maybe on the 442, it hindered aerodynamics rather it being neutral.

Its for looks.  (On MOST rides) 

 

The front part of the car above is boy racer, but functional...the rear part of the car...is purely for looks. 

Nothing wrong with that as it compliments the look and feel for what the Trans Am (Firebird/Firehawk)wants to pass of as.

Same with the Olds 442.  And Mustang.  On the Alero though, it makes NO SENSE at all as the Alero went for a sophisticated, luxury look.   I had a 1999 Alero coupe GLS...with that rear spoiler...HATED the spoiler.   I understand what you are saying. I agree with it. To a point.  I wanted to explain to you and others that care to read my post that on certain cars, rear spoilers, whether functional or not, work out, for others, not so much!  

For the record:  On a regular ecoboost Mustang or GT, a spoiler free rear works best for me too!!!

Edited June 20, 20196 yr by oldshurst442

I do like the wing on the new GT500..the car is over the top, so the wing is fitting in that context.  Likewise for the Z-R1.

Edited June 20, 20196 yr by Robert Hall

6 minutes ago, Robert Hall said:

I do like the wing on the new GT500..the car is over the top, so the wing is fitting in that context.  Likewise for the Z-R1.

I think the wings on these two are actually functional.

On GT I like the lip spoiler

Edited June 20, 20196 yr by ykX

Chrysler published an engineering paper on the directional stability & resistance to cross-wind benefits of tail fins in '57. Chryslers had large, vertical fins, and apparently the data was sound. I haven't ever seen this paper, but I've heard that the one detail that was left out is that the cars had to be going over 100 MPH for this benefit to come into play. Not withstanding that the 300-C was a 140+ MPH car, this seems unlikely to be put to the test in any real world scenarios. 

I imagine a similar circumstance exists for MOST sedan rear spoilers (and by extension: cross-drilled rotors). 

Edited June 20, 20196 yr by balthazar

That's one thing that gets looked past with cars that have functional rear wings that create actual down force.. You have to be getting after it for any benefit. At regular speeds and even interstate speeds there's little to no benefit. Your real down force occurs past 100mph but then again even a minimal amount is helpful when on a track. 

Great Engineering read on directional stability of fins. Yes talks planes but clearly can be put toward auto fins.

https://www.sciencedirect.com/topics/engineering/directional-stability

Surprised to see this 1979 paper from Nasa pop up on stability of fins, yes on rockets but clearly when scaled it can be applied to other applications.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19790009637.pdf

For the sake of it, I love this story on the history of Fins and their various designs. Lovely history coverage on auto Fins!

https://www.throttlextreme.com/fabulous-fins-look-history-tail-fin-styling/2/

@balthazar What are your thoughts on this read, interesting what they say about this Plymouth.

https://auto.howstuffworks.com/1951-1958-plymouth-belvedere6.htm 

1 hour ago, dfelt said:

What are your thoughts on this read, interesting what they say about this 

Looked at the last 2 links- factual pieces; I approve