OP
OP
Allentown
Well-Known Member
- Thread starter
- #31
Well i am really not an engineer and i could be wrong about all this but i will attempt to explain why i had the opinion that I did.
"Two-piece rotors offer some significant advantages, though, such as reduced weight as well as better heat dissipation, partly from the aluminum hat acting as a heat sink. Some two-piece rotors also offer increased airflow through the rotor because of the more open design where the hat meets the rotor face. Another big advantage is the ability to replace only the disc ring while reusing the center hat. This can add up to cost savings in many cases.”
Another advantage to this constuction is reduced heat-transfer to the vehicle's hub and wheel bearings. "
https://speed.academy/rotor-one-two...-right-disc-brakes-for-your-needs-and-budget/
He goes on to explain that the solid nature of a 1 piece rotor contributes to increased risk of warping where as two piece rotors are very loosely attached greatly reducing this effect. Some are actually floating with a spring loaded screw and it is impossible to warp the hat. They have those in the Wilwood 13886 racing series but because the rings bob around on those springs they make noise and people complain so they don't use them on the street kit (everything is a trade off but the risk of the warping problem occuring is still significantly reduced with the air channels and lose bolt points between the hat the the rings...even in the street kit). Another key component is that the racing inspired brakes usually have more heavily engineered air vanes inside the rotors which is where much of the increased cooling comes from. Of course, as i mentioned, you can get different rotors for the pp brembos as upgrades. I am only criticizing the 1 piece non slotted stockers on PP, not the entire Brembo line up. Lastly the street kit I bought does offer an advantage by being both slotted and drilled. While the current conventional wisdom is that purely slotted is better for the track (more surface area in contact with the pads) and being drilled can make the rings more prone to cracking. However, it is understandable that they still drill the street kits because the cross drilling does offer advantages in wet conditions where more gases are created from evaporating steam.
To be fair though, the shorter 14 inch height of the 14s vs the 15s COULD in theory keep them cooling better as well....(there are a lot of thermals i don't understand) but with the 14s a higher percentage of it's total surface area will be exposed to the air around it...on the other hand this could also make them HOTTER as the heat dissipated from the kinetic energy has to be stored in an area with smaller mass. On the other hand, having them both drilled and slotted (while reducing the surface area in contact with the pads) significantly increases the surface area exposed to the air...for dissipating heat yet again. I will wager that the surface area of the 14 inch slotted and drilled rotors is equal to or greater than the total surface area exposed to the air of your 15 inch flat rotors that come stock. (It is amazing how much additional surface area can be created by something like drill holes..it is much more than you would think initially)
The holes also function as a surface refresh mechanism to continuously refresh the brake pads and prevent additional build up and glaze. Supposedly this prolongs the life span of both pad and rotor. At any rate, it didn't slow down the Steeda race car one bit to run these rotors...and that size rotor did not seem to slow down the GT500 either, tires end up making the bigger difference at that point.
The downsize and one of the reasons your stockers are smooth is that it keeps the vast majority of shops from wanting to resurface them if you bond brake pad residue to them and they vibrate while braking....as the shop is afraid the slots and to a greater extent, the drilled holes will frack up their resurfacing machine. It is understandable that as an OEM ford would choose flat rotors as they are 1) cheaper and 2) can be resurfaced easier.
https://speed.academy/rotor-one-two...-right-disc-brakes-for-your-needs-and-budget/
I don't think it is something that is going to make much of a difference though unless you are pushing the brakes REALLY hard. Engineering Explained tried to test this in the 200 to 300 degree range and didn't find much difference. Science Science of Speed tested it on an actual track and found a 58.4 degree or 7.4% advantage on track for the two piece rotors and about a 53.6 degree or 12.4% advantage in the brake pads and calipers them selves.
Note he specifically points out there isn't much difference at street use temps.
Now in that case they were comparing much better designed slotted rotors in 1 piece kits to slotted designs in 2 piece kits (I assume)...the differences were not as impressive.
Comparing a two piece slotted to a solid rotor such as that which comes on the PP.....Steeda claimed a 200 degree difference between their two piece and the stock brakes.
While conducting rigorous on-track testing, Steeda's validation team measured up to 200 F temp reduction during the most severe conditions practical, with virtually no brake fade.
Now you have to separate the marketing BS from the facts and they word it like their kit is 200 F cooler than rotors that are at least drilled, but i suspect a sales pitch and they are actually citing that 200 over a completely smooth 1 piece rotor (which the stocks are). ...just my opinion.
https://www.steeda.com/steeda-performance-pack-front-brake-rotor-s550-555-6032
There really is no downside to a two piece design other than up front cost.
Which brings me to my close. I really did not set out here to "prove" anything or criticize stock PP1 brakes. I honestly don't thingk it matters that much nor do I think it was worth this huge discussion. Either will work perfectly well and either has additional choices for other pads and rotors. AS I SAID...the ones i bought were simply cheaper and i couldn't find any down side to saving the money while i WAS able to identify a few upsides. This is obviously a huge upgade from my stock setup and that was something i needed to do since i was running base model brakes and upgrading the suspension etc. already as well.
Did i screw any of the above explanation above up? Probably, there are others far smarter than me with more experience than me are welcome to jump in.
Sorting through the bull shit is 80% of the work.
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