Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB
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Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community - FT86CLUB (https://www.ft86club.com/forums/index.php)
-   Suspension | Chassis | Brakes -- Sponsored by 949 Racing (https://www.ft86club.com/forums/forumdisplay.php?f=59)
-   -   Why are expensive brakes better? (https://www.ft86club.com/forums/showthread.php?t=15155)

hotaka 08-20-2012 10:16 PM
Why are expensive brakes better?
 
Seems like an obvious question, but I can't find the answer. Even if you have a very nice braking system, your car's stopping ability is limited by traction, right (tires, downforce, car weight, and weight distribution, suspension)?

If your brakes are too good for the rest of your car, I feel that all it's doing is making wheel lock easier (and activate ABS).

How do they improve stopping distance?

Thanks

Xanatos 08-20-2012 11:01 PM
It depends on how you would like to drive your car. If your doing daily driving on normal roads a new brake kit won't be too much better. If you are on the track you ride the brakes alot and the brake rotor heats up and essentially fails to perform so you will see loss in braking power. The better brakes will have larger surface area so that temperatures don't get as hot and better materials that withstand more heat before breaking down.

You can always adjust the braking power if the kit ends up locking up too much.

CSG Mike 08-20-2012 11:22 PM
They don't improve stopping distance.

What they do is allow you to brake over and over and over, without overheating the system. Larger rotors offer more surface area for cooling, as well as more mass in the rotor itself to sink heat away from the pads. Larger opposed calipers offer more mass to sink heat away from the pads, and promote more even pad wear as opposed to the stock floating caliper.

Unless you're FI, the stock system with upgraded pads is generally "good enough". At least, in our experience it has been.

Here's a video of our BRZ braking over and over on sticky street tires; we suffered no fade, even running 5 laps back to back in 105+ ambient temps with race pads:

Turn 3: 129 to ~40
Turn 5: ~87 to ~45
Turn 8: ~100 to ~35
Turn 11: ~104 to ~45
[ame="http://www.youtube.com/watch?v=waCr19ZM640"]BRZ at Auto Club Speedway - YouTube[/ame]

BlaineWasHere 08-21-2012 12:19 AM
Ummm, larger brakes can also can also improve stopping distance. More surface area = more friction.

CSG Mike 08-21-2012 01:05 AM
Quote:
Originally Posted by BlaineWasHere (Post 392095)
Ummm, larger brakes can also can also improve stopping distance. More surface area = more friction.
Stopping distance is dictated by tires, not brakes (unless your brake bias is severely off). Can the stock brake calipers, rotors, and pads lock up the tires? Yes. That means that you have more braking power, than your tires have grip. Increasing braking power still doesn't address the lack of tire grip; the tire grip is the limiting factor in this case.

RallySport Direct 08-21-2012 01:17 AM
CSG Mike and Xanatos nailed it. Also, it comes down to driver preference. Usually when getting into aggressive street pads/ race pads you may find that a pad that is very expensive is the one that feels best to you, however you may also find that a very inexpensive pad is the right one for you, as it comes down to how you like the car set up and how you like it to feel.

Thanks,
Rick

BlaineWasHere 08-21-2012 01:39 AM
Quote:
Originally Posted by CSG Mike (Post 392181)
Stopping distance is dictated by tires, not brakes (unless your brake bias is severely off). Can the stock brake calipers, rotors, and pads lock up the tires? Yes. That means that you have more braking power, than your tires have grip. Increasing braking power still doesn't address the lack of tire grip; the tire grip is the limiting factor in this case.
What happens when tire grip exceeds brake force?

wheelhaus 08-21-2012 01:52 AM
Quick replies with dead-nuts correct info, nice!

Quote:
Originally Posted by BlaineWasHere (Post 392266)
What happens when tire grip exceeds brake force?
You simply run out of usable brake power and are required to apply excessive force, "standing on the pedal" comes to mind. This causes pads to overheat, glaze, break down and chunk off, uneven wear, fluid to overheat, boil, etc. Seals get damaged, too. Friction alone generates heat, but higher pressure allows that heat to transfer more quickly into the pistons and caliper body. Heat from the rotor can bleed into the steering knuckle and overheat the wheel bearings. Excessive heat is not good.

In addition to the benefits of hardcore track use mentioned above, another benefit of big brakes is lighter foot pressure and easier modulation.

edit- With extremely grippy tires and high power brakes, you eventually rreach a point of diminishing returns, where extra brake power doesn't really help, or the extra grip can't be utilized beyond a certain point. This is where aerodynamics come into play (read- downforce!) This changes everything and is really a topic for another discussion.

BlaineWasHere 08-21-2012 02:37 AM
Quote:
Originally Posted by wheelhaus (Post 392298)
Quick replies with dead-nuts correct info, nice!


You simply run out of usable brake power and are required to apply excessive force, "standing on the pedal" comes to mind. This causes pads to overheat, glaze, break down and chunk off, uneven wear, fluid to overheat, boil, etc. Seals get damaged, too. Friction alone generates heat, but higher pressure allows that heat to transfer more quickly into the pistons and caliper body. Heat from the rotor can bleed into the steering knuckle and overheat the wheel bearings. Excessive heat is not good.

In addition to the benefits of hardcore track use mentioned above, another benefit of big brakes is lighter foot pressure and easier modulation.

edit- With extremely grippy tires and high power brakes, you eventually rreach a point of diminishing returns, where extra brake power doesn't really help, or the extra grip can't be utilized beyond a certain point. This is where aerodynamics come into play (read- downforce!) This changes everything and is really a topic for another discussion.
So, if you have more tire grip than brake power larger brakes don't equal more stopping power to take advantage of tire grip? I understand the larger surface areas do better with the heat. I'm just trying to understand, and as you can see I'm struggling.

Vracer111 08-21-2012 02:50 AM
Quote:
Originally Posted by BlaineWasHere (Post 392095)
Ummm, larger brakes can also can also improve stopping distance. More surface area = more friction.
Surface area has nothing to do with 'more friction'...mu is mu... Now thermal capacity/ability - that's already been mentioned.

You want as small a brake system as possible for the application you need it to do reliably. The stock system is very good on track with sticky tires - all it really needs is a better pad compound. If not running more power than stock, then there is no need to 'upgrade' to a 'Big Brake Kit' for track duty (HPDE) - all you will be doing is adding a noticeable amount of unsprung weight with a very minimal increase in braking performance... degrading your performance when not on the brakes in other words.

fatoni 08-21-2012 02:54 AM
Quote:
Originally Posted by Vracer111 (Post 392409)
Surface area has nothing to do with 'more friction'...mu is mu... Now thermal capacity/ability - that's already been mentioned.

You want as small a brake system as possible for the application you need it to do reliably. The stock system is very good on track with sticky tires - all it really needs is better pad. If not running more power than stock, then there is no need to 'upgrade' to a 'Big Brake Kit' for track duty (HPDE) - all you will be doing is adding a noticeable amount of unsprung weight with a very minimal increase in braking performance... degrading your performance when not on the brakes in other words.
im not sure surface area has nothing to do with it. mu is a coeffecient

CSG Mike 08-21-2012 03:18 AM
I should add that a BBK can contribute to a more consistent pedal feel... but at a rather high price.

Quote:
Originally Posted by BlaineWasHere (Post 392266)
What happens when tire grip exceeds brake force?
In that unlikely scenario, getting a higher friction (mu) pad will get you the additional stopping power you need. However, if the tires really overpower the brakes, you'll likely overheat your braking system VERY quickly.

FrX 08-21-2012 03:22 AM
Quote:
Originally Posted by fatoni (Post 392416)
im not sure surface area has nothing to do with it. mu is a coeffecient

The formula for friction is: Ff = u * Fn

Ff = Friction force
u = Coefficient of friction
Fn = Normal force

There is no term for area. When the surface area is larger, the normal force is spread out over said larger area. Thus, each unit of area receives less force applied and the total force remains the same.

camelflage 08-21-2012 10:48 AM
Quote:
Originally Posted by BlaineWasHere (Post 392266)
What happens when tire grip exceeds brake force?
this is what you commonly find in the street scene with modified cars running fat grippy tires on 19 inch wheels and stock honda brakes.. the weight and grip of the wheels/tires will overheat the stock brakes and then you get super dorifto oh god cant stop rear-end a school bus kids on fire... so a BBK will help give the added pressure and heat management capabilities to slow down that extra rolling mass...


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