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
A system improvement without moving parts or electronics? The KISS principle for brakes? Wonderful.
As you note, these sorts of finned pads are fairly widespread in mountain biking, which does actually have some fairly rigorous requirements for braking especially on steeper downhill runs. They sort of work, if you swap out finned vs non-finned pads on Shimano brakes, there is a noticeable difference in brake fade as things get hotter. But mostly just using a bigger caliper with more mass and cooling area is usually a better solution, and the high end brakes used in competition (very few pros not being paid to run Shimano do so) mostly don’t bother with them.
After a night of reflection. I think there is a seed of a good idea here. But it’s going to take a lot more work. I think I could make it work… maybe. But you would have to be careful. Brake pads have an optimal temperature and getting them too cool will hurt performance.
Which gets to the big thing. Brake systems are systems. There’s a lot to them. This is a band aid for one particular problem, but it might cause problems elsewhere. I think there is a good idea in here, but not as a patch but a complete redesign of the brakes.
I was thinking the same thing – these are going to be cooling the pad, not the rotors. And the pads need to get to an optimal temperature to work properly. Especially if you have a BBK on something you also drive on the street like I do. These would probably hurt you there, as it would take longer for your pads to get heated up on a commute or trip to the store, and you’d end up hurting your rotors over time with too-cool pads.
Maybe, MAYBE you can put these things on just for track days. But if you care about performance to this degree, you already have a BBK. And if you have a BBK, your massive rotors, calipers, and pads already have more than enough surface area. Ducting will help much more at that point.
My idea is to have pads with deep fins behind them, to allow airflow through the caliper between the pad and the piston. Would take a complete redesign of the caliper and pads or your pads would be too thin to last. Also, because the pads would be a lot cooler, you would likely need to change your friction coefficient. If you added something like the old fan wheels that blew air into the slots between the pad and pistons, you could significantly change the temperatures, but with blowing air into the car underbody, you would be impacting downforce.
Entire system, I could see someone with stupid money really look into it (hello F1, I’m available if the price is right!)
I wonder if you’d be better off putting cooling fins on the brake pipes. Although I guess there’s not much flow so it might not help the fluid inside the caliper.
There might be a way to set up a heat siphon system where the fluid circulates from the heat into the tube, where it cools and then back into the caliper just from the changes in density. If the flow rate is low, just a normal brake tube would work.
I see you’re starting to post april fools articles early ..
Useless scam…once I got to the pic of the red caliper it was all over (I read the rest though) You bend them yourself, then it looks so unprofessional and not something to rely on since it looks/sounds like it doesn’t do shit. My Fuel Shark is way more reliable…those work great, right? Ha ha
I installed a second fuel shark in my extra 12V outlet.
Now I sell my extra gas back to the oil companies.
The way these were bent looks like a 3 year old did it. I’m out.
Perhaps make heat sinks which can clamp around the brake lines moving the hot brake fluid … Especially where they connect to the caliper.
Not really effective for two reasons:
There are brake systems that have a flow of brake fluid through the caliper when the brakes aren’t applied, but those are racing applications only.
I didn’t mean to cool the whole brake line. I know the column of fluid is just to transfer pressure from the booster to the piston. No circulation. Still some 4 inch heatsink wrapped could help IMHO to cool down the brake fluid right?
Anyways, the industry seems to go towards electric brakes. While I cannot speak for the reliability of electronic components very close to a very very hot rotor, I can see that that would remove the problem of deteriorating brake fluid.
Electric brakes are the same thing as electric motors. With EVs, almost all the braking is done with the motors already.
I think the ultimate setup for friction brakes is on aircraft. They don’t worry that much about cooling because the just spread the load over multiple disks and pads.
I’m sort of shocked that F1 brakes don’t mimic plane brakes in the front. Have the wheel spin say 3 sets of 360 deg Pads, while the hub holds 4 rotors. Under braking, you have at least 6 times the rotor area and 24 times the pad area. Spreading the same energy over so much more area leads to lower temperatures If you still need cooling, I would push water through the hub, which would cool the rotors and also the wheel bearings as well. If you let the water boil off during a race instead of recirculating, you could dump a ton of heat and keep the brakes under 110 deg C until you run out of water.
As for the rear brakes, since they have a hybrid system, using those electric motors to provide braking (and recharging the batteries) would do the majority of braking. And thus a normal brake system would be plenty.
I don’t mean regenerative braking but electric actuated brakes. So no brake fluid moving the pistons but an actuator (basically a tiny motor).
Those brakes recuperate no energy, they’re just there to replace the brake booster and brake fluid lines.
I haven’t seen these yet. I’m thinking of the advantages and disadvantages of them right now.
See for example https://www.evengineeringonline.com/zf-presents-a-new-purely-electro-mechanical-brake-system/
https://www.giuliaforums.com/threads/why-did-alfa-go-with-brakes-by-wire.59798/
Some Alfa Romeos already have this brake by wire (BBW) system for quite some years!
The rotor is the heat sink. As it heats up the friction reduces. These shims may move some heat away from the pad and maybe a tiny bit away from the caliper but it does nothing for the screaming hot rotor
Oh wild, I was thinking about something along these lines the other day.
I think one reason it’s been done on bikes is that their brakes are already at their limit, and giving the pads/rotors/calipers any more thermal mass would be adding ounces that bike riders really hate to pedal uphill with. In a car, adding a pound of caliper at the engineering stage has negligible drawbacks, so they all have big beefy brakes with plenty of inherent cooling.
I agree with the consensus, these cost more than better pads and a bottle of high-temp fluid, both of which are proven solutions and something you should get anyway.
LOL I did this in college as a project, and then show it in an assessment to get a trainee position at Ford.
I understand it’s a free market to charge whatever you want for a product but who in the world would pay $150-$200 for this?
Exactly.
That’s like 2 dozen eggs.
I don’t doubt that there is some slight improvement. Brake pads get really hot, and they stay in contact with the rotor the whole time while in use. They’re not rotating away from the heat in free air like the rotor.
What I’m completely sure of is that these aren’t doing $149-$200 worth of cooling.
Price them at five bucks a set and you’re probably getting your money’s worth if you track your car. Put ’em on a street vehicle and you’re wasting your money at any price.
OTH, the rotors are blowing some air past the pads when they’re not engaged with them. I’m not an engineer and don’t know how much air moves between the rotors and the pads. My non-engineer brain thinks the rotors are the limiting factor and not the pads which I think (?) are built to get hot, Perhaps, brake fluid is what needs to stay relatively cool. And no, I don’t want to circulate brake fluid through a heat-exchanger. That’s likely a level of complication that introduces new failure modes.
Maybe put fins on the wheels/rotors inside the swept surface of the pads that is aimed at them. I don’t know.
I am sure my rotors have never glowed like some do in photos I’ve seen from Le Mans et al.
Like many budget performance add-ons there is a strong whiff of gimmick about this. I sympathize with trying to upgrade your car on the cheap but if you’re at the point where you’ve upgraded fluid, pads and rotors on your stock setup and maybe added some ducting/deflectors and you’re still getting fade I think it’s time for a performance brake kit.
According to everything I’ve read about finned pads on mountain bikes, you’re better off upsizing your rotors rather than moving to finned pads. The forum commenter touched on this:
Increasing the surface area of the rotor allows it to shed heat much better than fins on the relatively small surface area of the pads. At least that’s the theory in the bike world.
Also, I follow a former World Cup rider turned YouTuber who doesn’t run finned pads because they tend to rattle more, and if he doesn’t need them then 99.99% of the world doesn’t either.
$200?!?!?
that’s just applying to brakes what’s been used in computers for decades…
Next they’ll add some fans on those radiators/heatsinks (because that’s what they are) or go straight on with watercooling.
Fans and water cooling are old school. Audi Quattros from the 80s had fans. The BBS wheels were fans that blew air across the brakes. I think someone else mentioned a system on some race car that had a system that used a windshield washer pump to mist water on the brakes.
Computers are behind the times. Modern brakes are ceramic and/titanium and handle insane temperatures. Modern brake fluid doesn’t boil until really high temperatures. The limit on today’s race cars is competition more than anything else. Modern race cars like F1 cars stop so fast that a driver that is 10% better at braking only makes up maybe a half a meter instead of having enough distance to safely overtake. This means that there is basically no passing, which is why DRS has been added to try to make the race not a parade.
Even an “old school” Nascar racer could have dramatically better brakes if the rules weren’t set to keep things so the braking zones are measured in feet and not inches.
Hmmm. On a rainy day, the first 1/10 of a second of brake application in my Saab 9000 after a long stretch of freeway was the pads getting rid of the water on the rotors and then getting down to business. I got used to it, but it was a little unsettling at first.
I had a car that I autocrossed regularly and drove on the street. I was having problems with overheating the brakes. I removed the shields behind the rotors so it could get more air flow around/over the rotors and it really helped on the track. But on rainy days, without that shield keeping water from splashing on the rotors, it sucked out loud. I put those shields back.
Anyone with old school drum brakes knows the idea of drying the brakes after going through a puddle. To this day, I tend to drag the brakes going through deeper puddles because that was how I was taught.