What do you if your brakes regularly get too hot during spirited driving? You could upgrade to larger rotors and calipers as we’ve explored before, or you could build some ducting to get more air flowing to the area. What a company called CoolShims offers is a bit different; its thin metal shims promise to add additional heatsinks to your brake system. Here’s a look at the rather strange product.
The basic idea is simple. CoolShims are, at heart, steel shims—thin pieces of metal that you slide in between the back of your brake pads and the pistons in the calipers. The metal shims are designed with lots of cooling fins to help them dissipate heat, ideally helping to keep both brake fluid and friction surfaces cooler for better performance. At least, that’s the theory.
These striking automotive accessories promise to deal with a common problem for sports cars—excess heat in the brakes. If your brake pads get too hot, they tend to lose their stopping power. In extreme cases, your brake fluid can boil, too. Either way, excess temperatures can leave your brake pedal soggy and your car careening off into a gravel trap. The idea behind these wacky shims is to avoid brake fade by helping critical brake components shed more heat.
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The CoolShims come in two main variants. There’s the high-profile variant seen above and directly below, with big obvious fins sticking up directly above the caliper. While this design creates a lot of surface area for heat transfer, it’s not ideal if your brakes don’t have much clearance with your wheels.
To solve that problem, CoolShims also makes a low-profile variant, as seen below. These use fins that are bent down to lay almost flat on top of the caliper instead.
Either way, installation is simple. You simply slide them in behind your brake pads in place of any factory shim that might have been there to begin with. In the case of the low-profile shims, you also have to bend the fins flat to ensure they don’t scuff against the wheels. CoolShims sells its product primarily via eBay, offering variants to suit everything from Chevrolet Camaros to Porsche Boxsters, Honda Civic Type Rs to Subaru BRZs.
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It’s true that fins, in general, make sense when it comes to dissipating heat. It’s all about increasing surface area—the greater the area of a hot object in contact with air, the more heat it can transfer.
So do these work? Well, we could do an engineering analysis and a bunch of instrumented testing, but that would take a lot of time and money. Let’s first explore what the company says about its own technology. Then, we can just look to see if the smart people that know how to go fast are using this technique, because motorsports is the crucible of engineering innovation.
The CoolShims website lays out the basic concept. “It conducts heat from the caliper piston to a heat sink located externally to the brake caliper through a high thermal conductivity dual metal composite developed by Four Products specifically for the extreme thermal conditions found in a high performance brake system,” reads the explanation. “Testing has revealed a greater than 20% decrease in maximum caliper piston temperature as well as significantly faster cool down times for a caliper employing CoolShim technology.”
Per the graph above, CoolShims has run some real-world testing of its products. In this particular trial, the company measured the temperature of brake calipers on a 1970 Datsun 240Z during a long mountain descent. One was fitted with CoolShims, while the other was left stock. The testing reportedly showed that the CoolShims equipped caliper ran 115 F cooler—405 F versus 520 F for the stock setup. The company also noted that the CoolShim caliper cooled much faster after the test.
Another extreme test was performed on a Meritor Quadralic brake caliper used in heavy vehicles like garbage and fire trucks. The rotor was brought to 550 F before it was put through repeated stops from 60 mph to 10 mph. After 33 stops, the stock caliper suffered seal failure with brake fluid at a sustained temperature over 140 F. However, with CoolShims fitted, the fluid apparently remained much cooler at closer to 115 F and the caliper did not fail despite 60 stopping cycles.
Of course, seemingly simple solutions with outsized performance often draw suspicion from the automotive world. That’s very much the case with CoolShims; one thread on BimmerForums sees posters citing concerns around wheel fitment and whether the shims have any positive effects whatsoever unless something has been done to the brake airflow. “It looks to me that you’ve gotta install a dryer vent pipe behind each wheel to achieve their test results,” posted Blacklane. “I would guess there is more mass in the brake rotor than in the caliper anyway, so any additional investment in air cooling would be better spent being focused on the center of the rotor, not the caliper,” noted emoore924.
However, another user apparently representing himself as the founder came in to defend his product. Per the post:
I did not post the question about CoolShims nor do I know the poster. I don’t have plans to make CoolShims for BMWs anytime soon so I am not trolling. I did log on when I saw this thread. I have a 2011 335d, so I have had an account here for a couple of years.
To address some of the comments:
1) They are heatsinks and the have been proven to decrease brake fluid temperatures. Is this decrease dependent upon airflow? Of course. This is true with all heatsinks. Testing was done on a brake dynometer with a 15 mph breeze to simulate airport conditions (we were testing on an airport firetruck caliper). We have also done on vehicle testing with similar results. But, yes, they need airflow to be effective.
2) With the majority of vehicles there aren’t wheel clearance issues because with a floating style caliper the heatsinks don’t stick out the top, but are tucked under the caliper to the inside of the wheel. The video on our facebook feed for the FRS/BRZ/GT86 shows that particular design.
At the same time, someone who claims to be the founder later admits in a 2015 post that they haven’t been much use in performance vehicles—despite still selling them to this day. As per the forum:
I obviously do care about CoolShims in general since it is my start-up manufacturing company, but I am not trying to make them for Z3s or any modern Bimmers. In the past I have made them for Porsche and there has been some success there. But what I have learned is that, generally speaking, the modern sports car has little need for them. Now I am mostly going to focus on pickups and RVs.
But back to our other theory—we can examine if this idea has any solid basis by seeing if it’s used in the world of motorsports. That’s because in motorsports, a good functional idea is typically either picked up by everybody or quickly banned by the relevant authorities. Indeed, we can see in Formula 1 that Brembo has used fins on its brake calipers. However, in this case, the fins are on the caliper body itself, rather than being a shim stuck behind the brake pad. There are titanium brake shims out there, and they’re meant for dealing with heat—but not dissipating it. Instead, they’re meant to act as a shield between your brake pads and the piston to help keep the brake fluid cooler.
Brembo fins its F1 brakes, but not with shims.
Ultimately, I simply wasn’t able to find evidence of racing teams using brake pad shims as a little boost to brake cooling. It’s true that race cars often have tight wheel fitment, with little distance between the brake caliper and the inside of the rim. Still, you’d think we might have seen it somewhere if a small piece of stamped steel really made a difference.
It’s entirely possible that CoolShims do have an effect. They might help cool your brakes to some degree. However, whether or not it’s to a significant degree that might noticeably improve your performance is harder to prove.
Funnily enough though, this technique is sort of used in mountain biking. Shimano makes brake pads with integrated cooling fins that stick out above the caliper. SwissStop and a range of other brands do, too, and they actually look pretty cool. The basic idea is to allow the pads to shed heat more easily so they don’t fade and lose effectiveness on longer downhill runs. It’s not clear how effective these are in improving braking performance.
My back-of-the-brain’s envelope take is that a shim stuck behind your brake pads probably isn’t going to do much for cooling. You’re only adding a bit of surface area, after all. You’ll likely find far larger gains just by improving airflow to your brakes, through ducting or otherwise. However, I’ll gladly be proven wrong if anyone does some independent instrumented testing to show us one way or another. In any case, as long you install them properly, they’re unlikely to do any real harm.
Image credits: CoolShims via eBay, via eBay
Personally, I think calipers get hot and brake fluid boils because of all heat radiating off the rotors, not going through the pad backing plate. Heck, sometimes it’s just a caliper piston rim touching the pad so the total surface area contact is like what, one square inch?
I suspect putting some nice juicy electric fans powered by some hyper brushless motors blowing high speed air at the brakes by temperature control would be more effective. Essentially just a leaf blower for brakes. It would be noisy as hell, but might work better than passive ducting which must create lots of constant drag. Temperature control of the fans could blow air on the outside caliper of a turn keeping it actively cooler. Pull the air from some high pressure area under the car. Hey, maybe this isn’t a terrible idea.
Here’s my take.
But realistically, on a modern vehicle with even spirited street driving, you shouldn’t have problems with boiling the brakes. Yeah, Nascar Cars are about as heavy as street cars and they do have brake issues that need all sorts of unique fixes. But if you are driving as hard as Bubba Wallace regularly, you might need to slow down.
Some people are really hard on this.
Do I think it would be worth it or effective? No, not really. But at least the physics are legitimate. (Unlike fuelshark.)
Seems like if you’re brakes are always too hot, you should just get different higher temp pad material and higher spec fluid. And improve airflow.
But they company founder sounded pretty rational. The examples for Porsche seemed silly, and he confirmed that they weren’t that effective.
But, his idea for trucks/RVs may not be the worst idea? Especially RVs? Some retiree, who usually drives a Toyota, and can’t even spell engine-breaking, suddenly heading through the mountains…
Unfortunately, someone who has the forethought to find aftermarket solutions to increase cooling to their brakes, knows it’s an issue, and probably knows not to ride the brakes downhill. So… I’m not actually sure about the market.
The physics may be real, (unlike the Fuel Shark) but the effect has got to be so statistically insignificant that we’ve reached the same outcome- Landfill fodder to separate $$$ from uninformed customers.
In some ways, capitalizing on legitimate science actually makes this product more insidious.
It’s not that I doubt the concept of a heat sink, I just doubt that this product will make a meaningful difference. If anything I would worry about people accidentally damaging their brakes while trying to install them. I don’t see an upside for anyone besides the company selling them.
The market for this is boy-racers with big wings, fart can exhaust, and stickers
You can also cool your brakes with my patented Super Natural Automotive Kooling Elixer Oil, or SNAKE Oil. I promise it comes from the finest imported snakes and isn’t canola oil with the label peeled off the bottle.
This is not to be confused with my Snake’s Oil, a special blend I formulated for lubricating your pet snakes. The fact that it looks and smells like old motor oil is nothing to worry about.
As a mountain biker I thought these looked a lot like what Shimano has been doing for a long time. It is interesting to note that Shimano bicycle brake systems use mineral oil instead of DOT fluid in their brake systems. The plus side of mineral oil is that it doesn’t absorb water which reduces the DOT fluid’s boiling point. The down side of mineral oil is that water in the system will pool in the caliper which is bad news if you have not bled your system recently and you ride in below freezing temperatures. Personally I use DOT based bicycle brake systems. DOT fluids are actually regulated with minimum performance specs while mineral oil is not and may or may not have a higher boiling point.
As long as you use mineral oil from the manufacturer or a reputable source it’s a non-issue. It’s also not just some mineral oil you grab off the shelf from the local store, it’s specifically formulated for brakes. I’ve always had much more luck from a maintenance standpoint with mineral oil based brakes over DOT ones.
One other nice thing about DOT is you can mix fluid from multiple brands and even 5.1, 4, and 3 while with mineral oil each formulation is different and mixing them is strongly discouraged. I’ve had really good luck DOT systems but I know plenty of folks that like their mineral oil based ones.
Hey, us roadies use these too! They definitely work and reduce brake fade, but my brakes are in essentially hanging out in the direct airflow. There’s no bodywork on a bike to speak of.
Fins originally started on the road side. When hydro first happened for curly bars, resin pads would get a little too hot for comfort. And this was the solution that avoided going metallic or to four pistons. Not big into the Mountain bikes anymore, but I don’t think finned pads are as common over there. As you could just go four-piston. And your going so much slower I doubt the fins do much.
For all the debate over DOT vs. mineral, I wonder if anyone has ever even heard of a mountain bike brake failure related to fluid. Plenty related to improper bleeding, sure, but that’s not the fluid’s fault and would happen no matter what you use.
I can’t recall even anecdotal evidence that fluid is a real problem in bikes, and in fact Seth from Berm Peak put baby oil in his brakes and found that they worked just fine, even on long downhill runs. Not that anyone should do that – proper brake fluid is not expensive enough to risk your life over – but still.
Here is a pretty extreme case where some people were having issues with mineral fluid at -20F. https://www.pinkbike.com/forum/listcomments/?threadid=228049
It seems like there are a lot more issues with mineral oil at very low temps. I’ve never ridden when it is below 0F and don’t plan on ever doing it. I do live in a wet area so I always run metalic pads so heat and fade has never been an issue even with 3000 ft downhill runs on a mtb or road/gravel bike. At this point one of the main reasons I go with DOT is that I have multiple bikes with the same brand of brakes and don’t want to have multiple bleed kits and fluids.
Ah, come to think of it that’s one reason I’m still running mechanicals on my fat bike. I’ve ridden them down to about -12 with no issues, and I don’t have a lot of interest in riding lower than that. I get nervous about riding in those kinds of temps because any problem mechanical or physical becomes life-threatening.
TL:DR: Add airflow (remove dust shields and add deflectors) before heat sinks.
You touched on the big x factor here several times… Airflow. The reason the mountiain bike shims work at transferring out heat to the air is because they’re in direct airflow. In a car, the rotor is pumping a lot of air, but there is very little flow directly above the pads. Sure, air is moving, but it’s indirect airflow.
I’ve converted racecars from ducted setups (that force air to the inside of the rotor) to deflector setups (with no dust shield, of course) that just flood the inside of the rotor with air. The rotor itself is a diffuser and will efficiently pump all the air it can, but the additional airflow also serves to cool the inner rotor face, caliper, and thus pads. In this setup, temps (monitored by temp paint on the caliper and rotor) were still managed perfectly in this GT350 racecar.
I’ve added control arm-mounted deflectors to one of my street cars that could not otherwise manage brake temp on the track and was able to extend the track time before overheating pads. You see Porsche and other manufacturers doing this on modern sports cars because it works and it’s very cost-efficient.
This feels like a product designed by someone who understands just enough to imagine a simple solution, but not enough to understand the limitations of their solution.
“I have seen heatsinks work. I think brakes could use a heatsink, but there is only so much space available. I’ll place a thin shim with the heatsink extending off of it.”
It’s better than the folks who think they can get unlimited energy by adding a belt-driven generator or something, but it really doesn’t look like it could do much. Too little material with airflow, plus the main portion of the material could interfere with any cooling already integrated.
Additional cooling for your brakes is completely unnecessary for 99.9999% of drivers.
But hey – there’s a sucker born every minute.
If they only sold cross drilled rotors to people who actually needed them, the companies would go broke.
Yeah, I just got a set for my car. I was warping brake rotors constantly. And I couldn’t figure out why. My Camry and my wife’s Sienna use the exact same rotors and she is more aggressive with the brakes.
After I got them, I found the problem. I wasn’t warping my brakes, I was imprinting them. Powerstop had a detailed procedure on how to bed in the pads so I wouldn’t have pad prints on my rotors that would lead to me thinking I had a warped rotor.
Details. When the pads are new, there is a binder (glue) that is still there. When the rotor gets hot, the glue melts. If the car is stopped and allowed to cool down to normal this glue sticks to the rotor and feels exactly like a warped rotor.
Look into bedding procedures. If I had done Powerstop’s procedure years ago, I would have saved a ton of money on brake rotors over the years.
But because I didn’t know about imprinting, I ended up with cross drilled rotors thinking I had a heat problem.
Is that our problem?
Caveat: I’m not a track rat
I’ve only over-heated my brakes to the point of being alarmed twice. Once I was way up in the mountains and being chased by Flo in her 90s Escort while she puffed back-to-back 120mm cigarettes. She was on a familiar road & in a hurry. I was in a Mercedes 300SD and almost didn’t make the last curve at the bottom of the 2nd mountain.
The other time I was running my mouth instead of downshifting to engine-brake and detoured through a ditch after a particularly steep stretch. I pay more attention these days
I don’t know much about brakes, but I do know enough about heat sinks to know there’s no way that thin piece of aluminum is actually doing anything to dissipate heat from the brake system. Race teams and really high performance cars use brake ducts. You want to cool your brakes for super cheap go to Home Depot and find some HVAC tubing.
I have some swamp land in Arizona for sale ??
This seems like a good example of “if it made sense, OEMs would do it”
Also, I don’t know anybody that actually runs finned MTB pads. It makes way more sense to draw heat away from the rotor.
The finned MTB pads do likely work to some minuscule degree- I think Shimano only claims something like “4% greater resistance to fade”. Still, I’ve never heard anyone claim to have noticed a real-world difference. And apparently they’re known for rattling.
Given how much larger the MTB finned pads are, (as a percentage of the overall brake assembly) there is no way in hell a sliver of metal the size of a credit card could affect an automotive brake system that weighs more than an entire bicycle.
Back to bikes, there is basically nothing on the market that compares with swapping your rotors for the next size up.
Exactly. There’s a very small window in MTB where that extra heat rejection is going to make a difference. Especially when big rotors make such a difference. If you’re overheating with big rotors and a regular pad you’re also going to overheat with a finned pad.
There’s at least a marketing case for the MTB ones though. The heat at the pad/rotor seems to be the main issue- I have never had brake fluid cause fading.
On a car, first thing to go tends to be the fluid. This company is claiming 140 degree F fluid causes caliper failure, destroying the credibility of their attempt at science.
I’ve had exactly 1 car this might help, 05 lgt which could out stop a sti exactly once, then super fade. On the track much the same you got a real slow once a lap.
94 SHO warped the rotors, not faded the pads. 96 brakes fixed. Note same caliper, bigger rotor.
04 sti set the pads on fire without affecting performance. Different pads there would fix.
04 f150 didn’t care, stopping was about the tire. It could stop fine fully faded from towing a trailer.
Pretty much everything else needed more brake before it needed more cooling. So a bbk of some kind minimum if you wanted.
I did the ’96 rotor/mounting bracket upgrade to my old ’94 SHO as well.
$150-200 is a LOT.
Username checks out.
True but one need not be a cheap bastard to question the value here.
Agreed. Not an issue perhaps if you already have vented rotors & cooling ducting: you are trying to get the last few % of gain.
For most of the cars I’ve had, a few dollars of dryer duct & a couple hours of creative routing would likely net much more cooling than this.
Or you could DIY your own cooling fins with a pair of tin snips and some empty beer or soup cans.
That seems to be the consensus. Why would I buy these when I can make something equally ineffective using the beer cans I already have in the garage? Doing it that way means I get to enjoy a beer or 2 while I waste time.
These seem like an interesting idea but if you’re really that concerned about it there are other ways to cool brakes. (I remember another guy 3D printing some air deflectors that scooped air and aimed it at the center of the vented rotor…. I think he copied them from something he saw on a 911….
Going back in time. Fan wheels.
Audi Quattros in the IMSA days had these wheels with fans in them that would blow air arcoss the brakes (I think they actually sucked air out).
https://www.classicdriver.com/sites/default/files/import/articlesv2/images/_de/4757/img05apop.jpg
On old C3s, the racers use the same trick with Corvair engine fans a decade before.
Oh, and I think those old fan wheels are cool looking too.
When i was doing 24hrs of Lemons i was digging around on the web and found out that there some race series where you couldn’t change the brakes from stock and people would put stainless steel shims between the pad and the caliper just because the heat transfer coefficient of Stainless is much less than the pad or caliper material…. It would keep the brake fluid cooler…. We never tried it…. We did big dryer ducting which worked as well…
Why don’t the caliper MFR’s put fins into the caliper design itself?
Because the rotor manufacturer has already put a bunch of cooling fins in the rotor. Cooler rotors keep the pads cooler.
Some manufacturers do. Before GM switched over to fixed calipers with the C7, the front and rear calipers on Corvettes were covered with fins.
Brake caliper seals are typically EPDM elastomers with upper steady state operating temp limits in the 250-275F range. So a failure due to 140F brake fluid would have me looking for inferior (often Chinese) materials.
Or a secondhand calliper was used for testing, with potentially worn seals, and then the magic doodads were tested with a freshly rebuilt calliper and new seals.
This is why engineering does a-b-a testing, rather than stopping as soon as you’ve got a result you want.
The issue with brake fade is that the fluid gets too hot, correct? Why not make the fluid in a loop, so the same hot fluid isn’t being used? You could even run it through a small radiator. You have one line going in, the second line could attach at the bleeder valve.
Has anyone done something like this?
Fluid boiling is an issue, but so is overheating of the friction material causing it to lose coefficient. Back in the early days of the TransAm, they had some setups with windshield washer pumps that sprayed water mist on the front brakes.
WRC rally cars had some version of this setup a while back where they circulated fluid around via some kind of active pump back to the reservoir to manage fluid temps
Welcome to 1980s Nascar. They had a loop with a little valve in the return leg. When you push with low pressure on the pedal, the little valve stays open and the fluid flows back to the reservoir. When the pressure goes high enough the valve closes and the pressure pushes the pads. I don’t know if Nascar still has this, but it used to be common to see guys going down the straight with there left foot fluttering on brake pedal to cool off the brakes before slamming the pedal down going into a corner.
Nascar has horrible braking problems with heat because they had ran small wheels (15″ for a LONG time) on a heavy vehicle.
It looks like I could make a redneck version of these in a few minutes with some tin snips. Slip them in with some CPU paste, and Bob’s your uncle!
Ever heard of a redneck Fuel Shark? It’s just a blue Christmas tree bulb that you force into the cigarette lighter.
Out of a couple of beer cans.
This is Redneck right?
Bob isn’t just your uncle. He’s your father, your brother and your great grandfather through marriage.
The upside is that there’s not much of a scramble finding accommodations for family reunions. 😉
Someone with a better engineering/ materials science background than I could do some back of the envelope calculations to confirm, but my sense is that both the volume of material in contact with the caliper/ pad and the surface area exposed for heat exchange are not significant relative to the overall caliper/ rotor.
Like the overlapping error bar sort of not significant.
Interesting idea, but unless the fins and what they’re attached to are thick enough I’m skeptical that they’d provide any meaningful heat sink effect. Think about it in terms of the heat sink on the CPU of your PC; if you’re not some maniac with a watercooled setup, your heat sink is a pretty thick chunk of milled and finned aluminum or copper with a cooling fan mounted directly to it. These basically sheetmetal pieces are probably better than nothing, but not by much.
Now if some design like this were integrated into the thickness of the backing plate, I could see it working. But then your development and production costs go way up. And you have to wonder why one of the big aftermarket braking companies like EBC or Hawk haven’t developed such a thing.
My main concern with these is the surface area to volume ratio. In my mind, it’d be hard to get the backing plate to conduct enough heat to the very ends of the fins. It’s just too long of a path through too small a cross section of metal. That said, even if the manufacturer is a biased source, test data is better than speculation.
I’d rather deal with heat at the source – cooling the pads and rotors better. Get some airflow to the center of the rotor to force feed the vented rotor, and let it cool the friction surface directly, rather than just trying to keep piston cool. If you want to do that, get higher temp fluid, and titanium brake pad shims have a much longer history of being effective.
They haven’t done an AIO yet. Quick, draw up a patent app, sit back and maybe get fabulously wealthy.
Call me cynical, but I’m getting major Fuel Shark vibes from these things. If they cost less I would say the site should buy a few sets and try them out to see if they get anything like the kind of benefits the company claims they found in testing. The “low clearance” versions look like something I could make with a few pieces of scrap sheet metal and my tin snips.
Well that’s not fair. The Fuel Shark makes zero sense. This at least makes sense. I’m still not convinced it actually works in a significant fashion. Heck, the fins may through off the airflow and make things worse! But at least it is a product that you can wrap your brain around.
Ha! As soon as I saw the header image I went “Oh well my Shimano and SwissStop brakes have these I know exactly what’s going on” and then I saw those very ones on the bottom of the article. It’s really fascinating tech, and something that’s been quite fun transitioning to all disc brake bikes is seeing that familiar car tech scaled down and made so much more visible
Same thing happened with me!
My thoughts on reading this article:
1. Is this the first instance of mountain bike technology trickling down to automotive?
2. Those look pretty thin and small relative to the pads, including when compared to the mountain bike ones.
3. I live in Michigan and didn’t bother with the vented pads for biking because there’s no need here.
4. Effectiveness of these is certainly questionable, but I’d love to see some independent testing.
For us average bicyclists, just upsizing the brake rotor would provide better gains.
Shimano also has finned rotors, with sandwiched aluminum in the disc to provide better cooling.
Long brake fade isn’t just because you’re in a mountain, but extended drops on the road (where speeds are higher than MTB, and rotors & calipers are smaller), and on some MTB trails with a lot of repeated high-speed drops would be cases where you might see some fade.
These are more of a road bike thing. And they do work to a noticeable degree racing or fast group rides. If you ain’t hauling ass though, it doesn’t matter. And carbon wheels and certain aerodynamics came out of cycling and into cars. I imagine we’ll see more as cycling is so efficiency oriented and its way cheaper to test shit.
Completely and utterly wrong on the part of finned pads being “more of a road bike thing”. Yes, they’re prevalent on road bikes now, but finned pads (and aluminum sandwich rotors) originated for mountain bikes with Shimano’s 2011 XTR gruppo’s “Ice Tech”. Long before anyone but niche builders were making disc brake road bikes.
Of course they’re going to make some sort of difference on mountain descents, road or off road. I haven’t seen any studies on them, though neither have I looked. Because I live in Michigan. The biggest descents we have are 500 ft maximum. Finned pads, sandwich rotors, and large calipers are not necessary here – with the possible exception that you’re tandem touring or some other niche high speed high weight rider. I’m already 210 lb + 60 lb of bike and gear and do 45+ mph descents on gravel, with 180/160 rotors and BB7 brakes and resin pads. No problems. But they’re not sustained. That’s only a couple hundred feet elevation max. If I were tandem touring in the alps of course I’d want the biggest rotors and vented everything.
Wrong, too, on carbon car wheels coming from bicycles. Michelin made carbon resin composite car wheels as early as 1971. Bicycles didn’t get carbon fiber wheels until sometime around 1994 with the Campagnolo Bora tubular wheels, though maybe there were some niche ones made earlier.
Aerodynamics? I’d have to see proof of trickle down to believe it.
I specified mountain bike trickle down technology because undoubtedly some early bicycle tech trickled down to autos – namely the pneumatic tire, which was first commercially produced by Dunlop in 1888 for the bicycle.