Let's try this again. Bigger Brakes Cannot Stop You Faster - Bigger Disc Leverage and more
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2022-11-06に共有
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Here's an interesting little piece of information. The amount of heat released by an average car during a single braking instance from a speed of 90 km/h is enough to boil two liters of water in just three seconds. All stock systems on all cars today are capable of doing this at least 4-5 times before brake fade starts occurring. This means that you can accelerate from 0 to 90 panic brake to a stop then accelerate to 90 again panic brake again and repeat this cycle at least 4 times before the slightest amount of brake fade can be measured. And even once brake fade starts it will be small and gradual and getting your stock brakes to fade to a point where they can't lock up the wheels and trigger ABS is next to impossible. This means that driving on the street cannot overpower the stock braking system. In fact if you ever need multiple panic brakes in a row while driving on public roads than there's something very wrong with your driving.
A lack of braking force does not exist on vehicles. Issue number two is that increasing braking force further cannot reduce your stopping distance.
And this is because your tires are the only thing on your car touching the ground...they are the only point of contact between your vehicle and the road surface. Once your overpower the grip that your tires provide there is nothing else left to overpower. Once the tire locks up and starts sliding increasing the brake force further will achieve nothing. Increasing the brake force via increased leverage or increased clamping force cannot increase the grip of the tires.
Increasing braking force further cannot reduce your stopping distance. And this is because we already have more than enough braking force to lock up the wheels. The comments on my previous video is make it obvious that many people associate brakes primarily with friction and torque....but a much better approach would be to perceive brakes as heat sinks. This is what they do. They convert the motion of the car or kinetic energy into heat and then dissipate this heat into the surrounding air.
Now we're going to compare three different cars to illustrate the extent to which modern cars really don't have an issue with braking.
The first one is the Mclaren Senna which is an 800 horsepower hypercar with absolutely amazing brakes state of the art carbon brakes. It has 390mm discs and 6 piston fixed calipers in the front. It gets from 0 to 100km/h in 2.6 seconds. The second car is the Mazda MX-5 ND has 280mm disc brakes and single piston floating calipers in the front. The 2.0 liter model gets from 0 – 100 km/h in just under 7 seconds. The third car is my very own 2009 Toyota Aygo has 247mm discs and single piston floating calipers in the front. It gets from 0-100 km/h in 14.2 seconds.
So as you can see we have staggering differences in brake systems and acceleration times. But not so much when it comes to braking distances. The Senna manages to come to a stop from a speed of 100kmh in 30 meters. The ND MX-5 manages 33.8 meters. I did a little test with the Aygo and did 10 panic brakes from 100 km/h and I managed an average of 35 meters.
So the McLaren Senna has 57% larger brake discs than the Aygo and has six times the number of caliper pistons. It is also 446% faster from 0 to 60 than the Aygo but it is only 16 % faster from 60 to 0.
So why is this the case? Why doesn't a million dollar hyper car dramatically outbreak a cheap little city car? The reason is that technology has long since reached the sensible limit of braking force.
Getting to a stop from 100 km/h in 35 meters takes less than 3 seconds and this in turn exposes you to forces of nearly 1G. Which is the limit of what the average driver can sustain on their body and still retain full control of their car.
Engineers are more than capable of making vehicles with ridiculous stopping distances. For example the F2004 which is Ferrari's formula 1 car from the 2004 season can come to a stop from 100km/h in just 16 meters. That's more than 2Gs of force. Formula 1 drivers are highly trained athletes capable of taking this load easily. On the other hand 2Gs would make many average drivers loose control of their vehicle. In fact F1 cars can generate as high as 5Gs of force when braking hard from high speeds. That's the sort of deceleration that can make some people pass out.
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#d4a #bbk #brakes
コメント (21)
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This man is a gift to the car community.
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The dude didn't insult the people who treat him "idiot" while proving his point. Real humility
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So in summary larger rotors and calipers can help shed off heat which will help delay or even prevent brake fade under extreme use such as a race track, but they do not decrease stopping distance. Also a video on master cylinder ratios would be nice.
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Great set of videos. I teach high performance driving to many new drivers and we always recommend they save their money by not upgrading to larger brakes (for a couple years at least while they are learning to drive). Pads? Yes. Fluid? Yes. Brake ducts? Yes. All for the same reason: heat management. Want to brake in shorter distance? Upgrade the tires.
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Remember y'all - this is the man who described what is happening with each "stu-tu-tu" noise in your turbo. You will never beat this final boss
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Personally, I appreciate the effort you put into explaining things and enjoy your videos.
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The people who got upset had just spent thousands on a big brake kit.
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Brilliant video! Spot on! I’ve been an Automotive Engineer for the past 14years, most of that time being in Brakes Engineering, working for Renault, Ricardo UK, Bosch Engineering and recently I moved to Jaguar Land Rover and I can confirm that ‘bigger’ brakes will only do one think, in the vast majority of cases, they will disturb the brake feel and the modulation as the brakes will tend to lockup faster as you very well stated in this video. Also if they are aftermarket brakes don’t be surprised if they are ‘noisy’. Unless you are racing, I wouldn’t even touch the stock brakes. We spend years getting the system sized correctly and the adequate pedal feel. More importantly most of the stock brakes are quiet, because of a very good reason we literally spend over two years in Brakes Refinement testing by making sure that the brakes are quiet, many millions of pounds are spent in that respect. With aftermarket brakes you cannot have the same level of Brakes Refinement as the aftermarket doesn’t have access to the same level of dyno, CAE and vehicle testing as an OEM does. Most of the braking systems are oversized anyway, as most OEMs design the braking system around the AMS test, which is not even a legislative requirement. The AMS test is extremely severe (10 consecutive brake stops from 100kph to 0) and it’s not a realistic use case. Consequently we end up with very big brakes and more importantly very heavy brakes. Therefore do yourself a favour and unless you are racing and you need the thermal capacity, then do not waste your money on shinny new ‘big’ brakes.
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Big respect not only for posting a follow up, but for maintaining your professionalism when others couldn't. This is a huge reason why this channel is my #1 when it comes to understanding automotive engineering with the intent of educating others - your commitment to providing content of exceptional quality shows in every video! Keep up the excellent work, and I can't wait for the next one! 👍
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I thought everyone knew braking distances were determined by the tyres? Oh well, excellent explanation for the physics though! 👍🏼
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I bought a car with Brembos fitted from new, the sort of things people upgrade to. I managed to cook them on the track to the point of having no braking no matter how hard I pushed. Not just brake grade, but brake vanish!! Came home, threw out the rotors and pads and upgraded those. Same brakes, same fluid, but better heat dissipation from the rotor and oars that were more heat tolerant and I now have a car that feels no different to drive, but the more I brake, the better it stops as heat gets into the system. So upgrading the right components, not the whole braking system, is where you’ll get the most benefit. Great video once again, love your stuff!
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The amount of times I've given up trying to explain to people that upgrading their brakes won't make their car stop any faster, it'll just make it easier to lock up their wheels when braking. People don't quite get it, even though everybody does understand tyres can only grip so much before they slip, it's like they know A and they know C but they can't quite work out how B figures into it.
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I appreciate that you don’t waste our time with jokes, or with constantly interrupting the video with other stupid and loud clips to make a joke. I appreciate that I can watch it without constantly bringing the volume up and down. And most of all, I appreciate the knowledge and fantastic explanations. Man you’re awesome.
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It is amazing to see how nervous and rude (to use polite terms) people can become when contradicted; but it is even more surprising to see your patience and kindness in re-explaining the arguments, despite all the insults given by uncivilized people
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You sir have consistently been my favorite automotive YouTuber for like 5 years. I seriously think you’re the best. Thank you
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I started with the same counterpoint of larger = more leverage. But your explanation is one of a PhD haha thank you for sharing the truth and saving me money
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Towards the end I can definitely say that the single best performance part I've ever bought for a car were lighter wheels. Lower unsprung weight dramatically improves handling and lower rotating mass has an exponential effect on acceleration and braking at higher speeds. At legal speeds though it doesn't make much difference.
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That was the most genuine “seek help” I’ve seen😂 he really does seem like a cool dude.
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I've learned more amazing facts about engines and cars from this Man in the last 3-4 years than basic to sophisticated knowledge since I was in my teens. Things that, as an engineering physicist, I should have known. Or figured out on my own. But "motorhead lore" and what seemed to be complicated but "common sense" had polluted my mind. If he says something about motor vehicles, I believe him. And then go back and figure out why I've looked at it wrong for decades. As an aside. I drove big heavy American V-8s from my teens (1974 -1987). Many were used and cheaper models and had front disk brakes and rear drum brakes. Although I started with a disc/disc 1953 Ford Flathead. I don't know if differential brake wear caused me a problem. I lived and went to school in LA for 4 years (1980-1984). To numerous to count times, I would come to partially blind freeway corner at ~65 mph only to see traffic at a dead stop ahead. I would stomp the brakes in my 350 V-8 1973 Monte Carlo. The rear drums would immediately lock up. But not the front discs. The car would end up, what seemed like, 80 degrees sideways with me steering into the turn. Totally in control directionally. Lots of screeching. I could, literally, control the sideways angle of the car by modulating brake pressure. I'd keep it sideways, in total steering control until I was pretty certain I would stop and gradually let off on the brakes. First slowly, and then immediately, it would snap back to straight forward. I was never trained at all in this type of driving. I just happened a lot in LA back then. The horrors of the 55 mph days. Going 55 mph on a LA freeway would get you killed. Many of you trained drivers are probably saying, duh? It happened often enough and was so amazing to me that I developed skills in using that technique. My previous cars were also heavy only with drum/drum brakes. This never happened with them. Obviously before ABS systems, did this mean that the proportioning valve was not correct or out of adjustment? Could I have corrected it to make rear lockup less likely? My personal observation is that a front heavy V-8 car stopped faster when controllably traveling sideways? Am I incorrect about this? I've always been leery of front disc/rear drum brake cars since then. Comments and thoughts are welcome. After that, I bought a used 1973 350 Corvette Convertible with front and rear discs plus 4 wheel independant suspension. Life was Grand. When I was 25 years old. Just Graduated Med School. I learned what a "women magnet" car really was. It was "chick magnet" back then. But I didn't want to offend any Karen's who police YouTube for micro aggressions. Only one more personal anecdote and a question. I promise. From 1982-1986, I also occasionally drove my girlfriends early 80s Toyota Tercel 4 cylinder low power and light weight 4 door. Narrow skinny tires on ~14" or less, steel rims. All factory parts. Not a "hotrod" car or one that inspired spirited driving ever. That car spun itself ( my interpretation) or I spun it >360 degrees on ~ 5 occasions. Always at normal driving speed. Every time, the road was coated with a wet watery mist on top of a normaly dry oily road surface. Never touched the brakes until it was out of control. I guess this is why F1 drivers get the Big Bucks? My first front wheel drive car, I realized that just letting off the throttle in a normal speed wide sweeping turn simulated only putting on the front brakes. The opposite of a RWD car. Instantly Initiating the out of control spin. I was lucky as no other traffic was ever around. An instant lesson in oversteer. I believe it was a dangerous vehicle. I've driven many later 1980s FWD cars without any problems. Any ideas on what was done to rectify this vehicle based design problem? Before ABS, traction control, etc.?
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413 viewers know car tech only from video games 😅
