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Big brake kit, does it decrease stopping distance?
- Thread starter doolar
- Start date
TLDR: As I've said for years, brake upgrade kits make the most difference at high speeds - generally, well above USA-legal speeds. AND, stopping distances will always be limited by available traction. Want shorter stopping distances? Mount stickier tires. Want less brake fade? Install larger brakes. Ideally, do both.
In addition, be careful with component selection or you could upset vehicle balance under max braking, and/or have an undesirable change in pedal feel / pedal effort / pedal travel.
Longer rant:
This video contains a mix of accurate information along with some cherry-picked data points that are misleading. Sure, the $2M supercar only stops in a slightly shorter distance than the econobox.... from 60mph! (And yes, it's largely due to available traction, not the brakes). Now try the same test from double that speed or more... 120mph or beyond. The results will be quite predictable. The econobox will take far, far longer to stop from 120-150mph than the supercar.
There was a lot of talk about larger diameter rotors producing more brake torque, which is correct. But I didn't hear any discussion about total swept area, which factors in the friction area of the pads, along with the total friction surface of the rotors. You can have different design rotors of the same diameter with VERY different swept areas / pad sizes. At the risk of opening a related debate, size isn't everything. Somewhat related, the number of pistons is also irrelevant... but generally as pad size increases, more pistons are needed to evenly apply pressure across the larger pad.
Another gaping hole in the video is assuming that the "stock factory brakes" always use factory original (Genuine OE) components. As soon as you replace those dirty, dusty OE brake pads with low-dust ceramics... all that goes out the window. Aftermarket pads (or rotors) can potentially DECREASE braking performance: brake torque, pedal feel, and stopping distances all could be affected.
Not clearly articulated in this video is the simple fact that if ABS is engaging during a stop, larger brakes will do NOTHING to improve stopping. If ABS is engaging, the ONLY way to improving stopping power is installing stickier tires (not necessarily "wider" tires). If ABS is not engaging... then you have more traction than braking power / brake torque, and yes "bigger" brakes should then reduce stopping distances.
Also not clearly explained is that bigger brakes aren't always intended to stop faster / stop better, but simply avoid brake fade and stop more consistently. Especially with repeated hard brake usage, typically experienced at a road course race track, or autocross. Stock brakes on typical passenger vehicles (NOT sports cars) are designed to manage a small number of hard stops, maybe a half-dozen or so stops from legal speeds, with minimal to no fade. Cars designed with performance in mind are generally expected to see track time and will have larger brakes that can handle repeated stops from extra-legal speeds without fade.
Which also circles back to a contentious statement I've made in the past: As power to weight ratio increases, in general braking power should increase as well. In an extreme example, let's say the Mazda MX-5 (8:30 in the video) was bumped from 180hp to 720hp. Would the stock brakes be adequate for stopping from 60mph with 4x the horsepower? Absolutely! But with the power to weight ratio increased 4x, the car could repeatedly accelerate back to (high) speed and be expected to repeat that stop much more quickly than possible with the stock power levels. Less cooldown time between stops will eventually result in fade (and, more rapidly fade vs stock power level), and loss of braking power, which would be much less likely to occur with stock power levels. Again, this is more of a racetrack scenario.
All of the above is Braking 101 and the fellow in the video seems to be missing some obvious points here, and hyper-focusing on brake performance (stopping distances) at low speeds with a limited number of repeated stops. Inside this narrow view angle, what he's saying is basically correct, but he's leaving out a lot of variables here.
In addition, be careful with component selection or you could upset vehicle balance under max braking, and/or have an undesirable change in pedal feel / pedal effort / pedal travel.
Longer rant:
This video contains a mix of accurate information along with some cherry-picked data points that are misleading. Sure, the $2M supercar only stops in a slightly shorter distance than the econobox.... from 60mph! (And yes, it's largely due to available traction, not the brakes). Now try the same test from double that speed or more... 120mph or beyond. The results will be quite predictable. The econobox will take far, far longer to stop from 120-150mph than the supercar.
There was a lot of talk about larger diameter rotors producing more brake torque, which is correct. But I didn't hear any discussion about total swept area, which factors in the friction area of the pads, along with the total friction surface of the rotors. You can have different design rotors of the same diameter with VERY different swept areas / pad sizes. At the risk of opening a related debate, size isn't everything. Somewhat related, the number of pistons is also irrelevant... but generally as pad size increases, more pistons are needed to evenly apply pressure across the larger pad.
Another gaping hole in the video is assuming that the "stock factory brakes" always use factory original (Genuine OE) components. As soon as you replace those dirty, dusty OE brake pads with low-dust ceramics... all that goes out the window. Aftermarket pads (or rotors) can potentially DECREASE braking performance: brake torque, pedal feel, and stopping distances all could be affected.
Not clearly articulated in this video is the simple fact that if ABS is engaging during a stop, larger brakes will do NOTHING to improve stopping. If ABS is engaging, the ONLY way to improving stopping power is installing stickier tires (not necessarily "wider" tires). If ABS is not engaging... then you have more traction than braking power / brake torque, and yes "bigger" brakes should then reduce stopping distances.
Also not clearly explained is that bigger brakes aren't always intended to stop faster / stop better, but simply avoid brake fade and stop more consistently. Especially with repeated hard brake usage, typically experienced at a road course race track, or autocross. Stock brakes on typical passenger vehicles (NOT sports cars) are designed to manage a small number of hard stops, maybe a half-dozen or so stops from legal speeds, with minimal to no fade. Cars designed with performance in mind are generally expected to see track time and will have larger brakes that can handle repeated stops from extra-legal speeds without fade.
Which also circles back to a contentious statement I've made in the past: As power to weight ratio increases, in general braking power should increase as well. In an extreme example, let's say the Mazda MX-5 (8:30 in the video) was bumped from 180hp to 720hp. Would the stock brakes be adequate for stopping from 60mph with 4x the horsepower? Absolutely! But with the power to weight ratio increased 4x, the car could repeatedly accelerate back to (high) speed and be expected to repeat that stop much more quickly than possible with the stock power levels. Less cooldown time between stops will eventually result in fade (and, more rapidly fade vs stock power level), and loss of braking power, which would be much less likely to occur with stock power levels. Again, this is more of a racetrack scenario.
All of the above is Braking 101 and the fellow in the video seems to be missing some obvious points here, and hyper-focusing on brake performance (stopping distances) at low speeds with a limited number of repeated stops. Inside this narrow view angle, what he's saying is basically correct, but he's leaving out a lot of variables here.
IMOP, If your stock brake system on your E500E is in top condition you should be satisfied with their performance. Unless you plan on racing your car the close to stock brakes should be more than sufficient. By close to stock I mean having upgraded pads and rotors only.
Great info Dave, just as expected from you!TLDR: As I've said for years, brake upgrade kits make the most difference at high speeds - generally, well above USA-legal speeds. AND, stopping distances will always be limited by available traction. Want shorter stopping distances? Mount stickier tires. Want less brake fade? Install larger brakes. Ideally, do both.
In addition, be careful with component selection or you could upset vehicle balance under max braking, and/or have an undesirable change in pedal feel / pedal effort / pedal travel.
Longer rant:
This video contains a mix of accurate information along with some cherry-picked data points that are misleading. Sure, the $2M supercar only stops in a slightly shorter distance than the econobox.... from 60mph! (And yes, it's largely due to available traction, not the brakes). Now try the same test from double that speed or more... 120mph or beyond. The results will be quite predictable. The econobox will take far, far longer to stop from 120-150mph than the supercar.
There was a lot of talk about larger diameter rotors producing more brake torque, which is correct. But I didn't hear any discussion about total swept area, which factors in the friction area of the pads, along with the total friction surface of the rotors. You can have different design rotors of the same diameter with VERY different swept areas / pad sizes. At the risk of opening a related debate, size isn't everything. Somewhat related, the number of pistons is also irrelevant... but generally as pad size increases, more pistons are needed to evenly apply pressure across the larger pad.
Another gaping hole in the video is assuming that the "stock factory brakes" always use factory original (Genuine OE) components. As soon as you replace those dirty, dusty OE brake pads with low-dust ceramics... all that goes out the window. Aftermarket pads (or rotors) can potentially DECREASE braking performance: brake torque, pedal feel, and stopping distances all could be affected.
Not clearly articulated in this video is the simple fact that if ABS is engaging during a stop, larger brakes will do NOTHING to improve stopping. If ABS is engaging, the ONLY way to improving stopping power is installing stickier tires (not necessarily "wider" tires). If ABS is not engaging... then you have more traction than braking power / brake torque, and yes "bigger" brakes should then reduce stopping distances.
Also not clearly explained is that bigger brakes aren't always intended to stop faster / stop better, but simply avoid brake fade and stop more consistently. Especially with repeated hard brake usage, typically experienced at a road course race track, or autocross. Stock brakes on typical passenger vehicles (NOT sports cars) are designed to manage a small number of hard stops, maybe a half-dozen or so stops from legal speeds, with minimal to no fade. Cars designed with performance in mind are generally expected to see track time and will have larger brakes that can handle repeated stops from extra-legal speeds without fade.
Which also circles back to a contentious statement I've made in the past: As power to weight ratio increases, in general braking power should increase as well. In an extreme example, let's say the Mazda MX-5 (8:30 in the video) was bumped from 180hp to 720hp. Would the stock brakes be adequate for stopping from 60mph with 4x the horsepower? Absolutely! But with the power to weight ratio increased 4x, the car could repeatedly accelerate back to (high) speed and be expected to repeat that stop much more quickly than possible with the stock power levels. Less cooldown time between stops will eventually result in fade (and, more rapidly fade vs stock power level), and loss of braking power, which would be much less likely to occur with stock power levels. Again, this is more of a racetrack scenario.
All of the above is Braking 101 and the fellow in the video seems to be missing some obvious points here, and hyper-focusing on brake performance (stopping distances) at low speeds with a limited number of repeated stops. Inside this narrow view angle, what he's saying is basically correct, but he's leaving out a lot of variables here.
And I was utterly satisfied with the SA-kit I bought from you all those years ago, no matter what any YouTuber says. 
The purpose of me posting this is just this, to go in depth on the topic. 500Eboard is capable of actually discussing things properly, and there’s a lot of knowledge here to be shared.
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