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Old 04-24-2020, 02:09 PM   #11 (permalink)
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Quote:
Originally Posted by JulianEdgar View Post
Of course, absent from this discussion is the need for brake cooling, which from a manufacturer's perspective is probably at least as important as aerodynamic efficiency. (And I think it is pretty important too!)
Only recently have brake rotors been exposed by alloy wheels. Up through the 1990s brake rotors were covered buy big steel wheels and it was never a problem.

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Old 04-24-2020, 03:15 PM   #12 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
Only recently have brake rotors been exposed by alloy wheels. Up through the 1990s brake rotors were covered buy big steel wheels and it was never a problem.
Steel wheels that invariably had brake ventilation openings in them.
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Old 04-24-2020, 04:11 PM   #13 (permalink)
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Typical wheel found on US cars trucks and SUVs through the 1990s. Now resides on my trailer.


Auto makers put vents on wheels because they look cool and make the wheel lighter, they don't really start to make any functional difference until you are on a race track.
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Old 04-24-2020, 06:30 PM   #14 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
Typical wheel found on US cars trucks and SUVs through the 1990s. Now resides on my trailer.


Auto makers put vents on wheels because they look cool and make the wheel lighter, they don't really start to make any functional difference until you are on a race track.
Brake cooling has been part of road car wheel design for at least 50 years. For example, a textbook I have on brake design that was published in 1967 mentions it.

In a current context, a recent Porsche paper I was reading on the development of an aerodynamically slippery wheel spends over half that section on the difficulties of developing an aero wheel that doesn't too adversely impact brake cooling. In fact, you can see exactly how much extra drag they accepted in order to achieve adequate brake cooling.

I think every reference (text or paper) that I read when writing the section in my book on wheel drag mentions the importance of brake cooling.
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Old 04-24-2020, 07:15 PM   #15 (permalink)
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Alternatively, just make brakes that can take the heat:


youtu.be: Crazy Red Hot Brakes Compilation! *HOT*
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Old 04-24-2020, 09:17 PM   #16 (permalink)
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Don't drive like that and you won't need major brake cooling.
Those brake rotors probably aren't steel or cast iron.
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Old 04-27-2020, 04:06 AM   #17 (permalink)
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I actually did this video a few weeks ago but only just released now.
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Old 04-27-2020, 10:53 AM   #18 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
Don't drive like that and you won't need major brake cooling.
Those brake rotors probably aren't steel or cast iron.
That's right. I hardly use my brakes even in "stop-n-go" traffic because of engine breaking and EOC. Certainly not heavily. My brake pads last forever.
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Old 04-27-2020, 01:28 PM   #19 (permalink)
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Quote:
Originally Posted by JulianEdgar View Post
Brake cooling has been part of road car wheel design for at least 50 years. For example, a textbook I have on brake design that was published in 1967 mentions it.

In a current context, a recent Porsche paper I was reading on the development of an aerodynamically slippery wheel spends over half that section on the difficulties of developing an aero wheel that doesn't too adversely impact brake cooling. In fact, you can see exactly how much extra drag they accepted in order to achieve adequate brake cooling.

I think every reference (text or paper) that I read when writing the section in my book on wheel drag mentions the importance of brake cooling.
i thought they had asbestos brake pads back then
I saw a set of pads that said "now without asbestos". that my grandpa had in the garage that was sitting there for ages..
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Old 04-27-2020, 06:54 PM   #20 (permalink)
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Quote:
Originally Posted by JulianEdgar View Post


I actually did this video a few weeks ago but only just released now.
Interesting that the wheel with radial slots ended up with the second-largest delta-Cd. After looking at the pictures of the XL1, Insight, and Tesla Model S wheels in the other thread with their circumferential openings, I was reminded that most manufacturers today have shifted to radial slots on their economy cars and lower-drag cars. For example, the Tesla Model 3:



The 2016+ Civic:



Hyundai Ioniq (the base Blue trim has even smaller openings than these!):



Hyundai Sonata Hybrid (until 2020, the new one has more openings):



Honda Accord Hybrid:



...and many others.

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