nitroman wrote:
The higher your deceleration level, the more weight transfer takes place, reducing the weight on the rear tires and increasing it on the front If anything, you’d now want to decrease the rear effectiveness, which the "mondo" Wilwood brakes do. Vehicle stability under braking requires that the rear brakes do NOT lock before the front brakes. When an OEM is designing a brake system, they 'size' the system components (calipers, rotor OD) to generate the proper amount of torque at both ends of the vehicle so that the front brake force exceeds its peak traction first. At this point, the front brakes lock and the car slides in a nice, stable straight line.
The Potential Impact of “too big” Front Brakes:
Considering front bias, can you have too much bias? Certainly. Too much front brake will leave the front doing more work than necessary and possibly lead to over heating. But too much rear can create an unstable and "tail happy" feeling making braking quite dangerous. A well-designed brake system should always lock the front first. If the rear wheels lock, the car will spin around. In fact, the purpose of rear proportioning valves is to ensure that line pressure cannot rise to the point of rear lock up.
Fortunately (from a safety standpoint anyway), big-front-brake suppliers adapt a mondo rotor and caliper package to a vehicle. They end up actually increasing the FRONT bias. However, they are not pushing the vehicle toward instability. If they were, every one of them would have been sued out of existence.
I do not totally agree with what you are saying here and it is a little miss leading.
Lets take a look at weight transfer, the amount of weight transfer is limited by tyre grip so as you can lock the fronts with the standard brake setup saying you get more weight transfer with big brakes is a myth, a simple physical impossibility.
Ok I agree that locking the rears first is not a good thing, but then neither is having too much front bias, in fact with too much front bias you can increase yes increase the overall stopping distance.
I agree that the manufacturer does endeavour to get the balance of the brakes correct but you have to take into account changing road surfaces, conditions and different tyres, all of which effect the maximum load that can be placed on the wheels before they lose grip. They do extensive testing on a variety of surfaces over a long period of time to check they have it correct, and adjust the setup accordingly.
I agree you can have too much front bias but where did this heat bit come from?
The standard brakes do not cope very well with aggressive driving, never mind track use, this we all I feel know, by increasing the size of the fronts you should get better heat dissipation as this is what brakes do. They take the kinetic energy and simply convert it to heat and then dissipate the heat in to the surrounding air.
If you increase the fronts beyond a certain point then the amount of braking force that can be applied to the car will be overall reduced
Losing traction on the front tires is not as bad as the rear. You usually just plow forward until the driver lightens up enough on the pedal to regain control. Whatever the percentage is for your particular car, the front tires should lock up
slightly before the rear tires under hard braking.
Most manufacturers tune the brakes setup to be front bias, they like our cars to be front-biased in all conditions achievable by the tires offered on the vehicle. This helps to insure vehicle stability under braking by the mass public. If we measure stopping distance of the vehicle as delivered from the showroom floor, we have a good benchmark for a vehicle with a 5% to 10% front brake bias. That 5 to 10% is not the brake split e.g. 70/30 but a % bias to the front such that on a car with 70/30 split the ideal is around 65/35.
You can be certain of one fact if you increase the front bias your braking distance will go
up yes I said
up.
If you put a car with standard brakes (in good condition) up against a car with too much front bias the standard car will stop in a shorted distance, FACT.
And lets not forget that changing the pads alone can change the bias of the brakes e.g going from say a 35u to a 45u pad can change the bias from say 71/29 split to 76/24.
I have a set of the "Q" compound pads but no experience with them; hopefully they'll bite well enough cold. I don't track the car but "spirited" road driving does happen occasionally. I'll have to favor a pad with good bite when cold over extended performance when hot. On a previous cars, I've used Axxis Metalmasters with reasonable results - still not great cold but heat quickly and bite like mad when warm. I haven't seen them mentioned here in the forum so maybe they're not available in the UK.
