Anyone have any brake questions?
#601
When our car left the factory, the brake system were already front bias by some margin... Why would you wish to increase this bias and not try to use the rear braking "reserve". As long as you're not blocking the rear wheels before the font wheels (with a safety margin), i thought that you would apply as much rear bias as possible...
... but i'm not sure i "get it right" yet....
#602
You can go back and watch in car videos of the guys pulling their hand off the wheel on the straight, making an adjustment, going into the corner.
Although sometimes it was bias for the corner, the engineer telling them to control temps at one end, etc.
#603
Imagine what happens when you brake hard on a bicycle or motorcycle. If you have enough grip, you can brake so hard that the rear wheel leaves the ground. (Look at sport/racing motorcycles and you'll notice that there are two front brake disks and only one in the rear, and even then, the front ones are much, much bigger.)
A car has a longer wheelbase and a lower centre of gravity than a bike, so of course you won't have the rear wheels in the air, but the same principle of forward weight transfer during braking applies. Get grippier tires and you get more forward transfer, meaning that the rear wheels will have less weight over them and lock earlier. The result is that more of the braking is done by the front wheels.
Go the other way and drive on snow or ice, where there isn't enough grip available to get lots of weight transfer, and you'll notice that an otherwise balanced setup will lock the fronts prematurely.
#604
if during your test, you keep the same tires you would see no difference in one stop. you would notice the 11.75" kit components would last longer, and be more consistent over multiple stops.
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#605
Can someone explain to me why there's such a disparity over brake bias recommendations? On one hand, you've got people recommending to take out the stock prop valve altogether on an otherwise stock setup, and on the other you've got track gurus running more aggressive pads on the front than the rear even with big brake kits.
Is it as simple as that you track guys are running such grippy tires that they can handle and/or need that much front brake during forward weight transfer?
On my street car, on moderate street tires, I definitely feel like the fronts lock prematurely on my square-padded, stock-braked setup. Am I wrong?
Is it as simple as that you track guys are running such grippy tires that they can handle and/or need that much front brake during forward weight transfer?
On my street car, on moderate street tires, I definitely feel like the fronts lock prematurely on my square-padded, stock-braked setup. Am I wrong?
it can be as simple as the grip of the tires. Me an Emilio have a tendency to disagree and that is human nature, but if you ask us both what the single most important component on a race car is, we will both say tires. now adding tires with a higher coefficient of friction will result in more body roll. this is simply from the tires are now overloading the springs.
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#606
I'd counter by saying that brakes are more important. Sure, a sticky tire might allow .1 or .2 more G force in the corner but that 1 second lap time increase can be matched by being able to brake later with better brake pads.
I'm amazed at the number of guys who take their 400HP car to a track day with street pads. One track day I was at, a guy with a new BMW had cooked his brake pads so badly that they were hissing from the resins melting, and he came in before the first 20 minute session was over.
I'm amazed at the number of guys who take their 400HP car to a track day with street pads. One track day I was at, a guy with a new BMW had cooked his brake pads so badly that they were hissing from the resins melting, and he came in before the first 20 minute session was over.
#607
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I'd counter by saying that brakes are more important. Sure, a sticky tire might allow .1 or .2 more G force in the corner but that 1 second lap time increase can be matched by being able to brake later with better brake pads.
I'm amazed at the number of guys who take their 400HP car to a track day with street pads. One track day I was at, a guy with a new BMW had cooked his brake pads so badly that they were hissing from the resins melting, and he came in before the first 20 minute session was over.
I'm amazed at the number of guys who take their 400HP car to a track day with street pads. One track day I was at, a guy with a new BMW had cooked his brake pads so badly that they were hissing from the resins melting, and he came in before the first 20 minute session was over.
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Let's face it, all of the components are important and need to be balanced to work well together.
#610
your not allowed to bring up ebc.. nope not allowed.
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#612
Complains about 400hp bimmer guys with Street setup, matches 1.6 yellows with Hoosiers.... OK.
Yes, the whole system needs to work. But you choose the tires based on lap times you're shooting for, and then match the pads (and suspension) to the tires, not the other way around.
Yes, the whole system needs to work. But you choose the tires based on lap times you're shooting for, and then match the pads (and suspension) to the tires, not the other way around.
This year I ran on the full course at Pittrace and it's a definitely harder on brakes. There's probably 5 aggressive braking zones and a couple other places where you'd use the brakes to set the car depending on the line you take.
The full course at Pittrace is now longer than Mid Ohio.
#613
F1 caliper test
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#614
I have a question on increasing the rotor size. With some upgrades going to a larger rotor also increases the rotational mass. Yes you get a larger, better heat sink to dissipate the heat, but at what point is there a diminishing returns problem. Let's say if the rotor weight increases by 1.5-2 lbs for front right and left (total 4 lbs). Let's say one car is driven/trailered to the track and the other is a fun street car with 1-2 HPDE a year. Both have 300 whp.
I guess another way to see it is sport rotors and calipers on the front and then extending the caliper bracket to fit the Mini cooper 11.5" rotors.
Thanks for your help
I guess another way to see it is sport rotors and calipers on the front and then extending the caliper bracket to fit the Mini cooper 11.5" rotors.
Thanks for your help
#617
I have a question on increasing the rotor size. With some upgrades going to a larger rotor also increases the rotational mass. Yes you get a larger, better heat sink to dissipate the heat, but at what point is there a diminishing returns problem. Let's say if the rotor weight increases by 1.5-2 lbs for front right and left (total 4 lbs). Let's say one car is driven/trailered to the track and the other is a fun street car with 1-2 HPDE a year. Both have 300 whp.
I guess another way to see it is sport rotors and calipers on the front and then extending the caliper bracket to fit the Mini cooper 11.5" rotors.
Thanks for your help
I guess another way to see it is sport rotors and calipers on the front and then extending the caliper bracket to fit the Mini cooper 11.5" rotors.
Thanks for your help
Rotational mass is 4x as important as sprung weight. it is by far the most critical area on the car to add or subtract weight from. for example lets say you add 4lbs per corner. 4lbs X 4 wheels = +16lbs of rotational mass that would feel the same as adding 64lbs into the chassis.
so to answer your question. it's always bad to add more rotational mass. when i'm building a kit i use a rotor with an aluminum hat. That way i can increase rotor size AND lose a little rotational mass.
On the 350z with brembos the PFC two piece rotor is 5lbs lighter then the oem piece. if you can get that on all 4 corners it would feel like you where pulling 80lbs out of the chassis.
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#618
All the extra mass of the larger mini rotor also has a larger moment of inertia than the sport rotor, simply because it's a bigger rotor.
If you were to change one 15" for another heavier but wider 15", the moment stays the same, mostly. If you were to step up to 17's, the rotational weight has a larger moment again due to the larger diameter, and any extra weight is extra taxing.
Have you tested when using a smaller, lighter rotor is beneficial, since it's such a massive 4/1 ratio?
If you were to change one 15" for another heavier but wider 15", the moment stays the same, mostly. If you were to step up to 17's, the rotational weight has a larger moment again due to the larger diameter, and any extra weight is extra taxing.
Have you tested when using a smaller, lighter rotor is beneficial, since it's such a massive 4/1 ratio?
#619
All the extra mass of the larger mini rotor also has a larger moment of inertia than the sport rotor, simply because it's a bigger rotor.
If you were to change one 15" for another heavier but wider 15", the moment stays the same, mostly. If you were to step up to 17's, the rotational weight has a larger moment again due to the larger diameter, and any extra weight is extra taxing.
Have you tested when using a smaller, lighter rotor is beneficial, since it's such a massive 4/1 ratio?
If you were to change one 15" for another heavier but wider 15", the moment stays the same, mostly. If you were to step up to 17's, the rotational weight has a larger moment again due to the larger diameter, and any extra weight is extra taxing.
Have you tested when using a smaller, lighter rotor is beneficial, since it's such a massive 4/1 ratio?
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#620
it really depends on the racing and the car. In time trials dedicated car yes we'll use a narrow (lighter) rotor of not carbon. Track day and Club racers use an endurance style brake kit (as big as it can be), just for cost reasons. most of the time we have wheel size limits. the car was built around running a certain tire compound and size. to that we will try and fit as large of a rotor as we can. the larger rotors allow us to run less compound and provides better feel.
Right, I get it, but it seems to be a compromise to fit the situation.
You are trying to balance more heat dissipating mass, more rotational mass, and (possible) increased cost of running a two piece rotor.
It seems like if you do just a few HPDE events, could a case be made for taking the rotational weight hit for increased braking performance?