Azuremen
Braking bias will affect weight transfer ONLY if it affects the rate of decelleration.
It does not matter whether the front wheels are slowing the car, or the rear. If either slow the car at rate x, then the weight transfer (z) will be x*y. So, weight transfer is like so...
z = x * y, z = weight transfer; x = braking power; y = fixed value of weight moved by x stoping power.
Typically, a rear bias will make it so x is less... so the equation would shift like so
z = (x - q) * y, where q = variable based on brake bias.
The reason why suspension loads would be different is because the car simply is not slowing down as quickly.
heh, nice Azuremen, the nerd in me is just itching to get out
if you want to pick up the technicality we can bring in the momentum equation and Newtons first and second laws of motion. though, this is still very 'high school' physics, it should demonstrate what going on with reasonable accuracy.
First Law: "an object in motion remains in motion unless acted on by an external force"
Second Law: the rate of acceleration of an object is equal to the force applied, divided by the object's mass
a = F/m
in this case the vehicles deceleration is equal to the braking force (a negative force since it resists forward motion) divided by the vehicle mass
Momentum Equation:
M = mV <-- momentum = (mass)(velocity)
to solve this accurately over the braking period would require a little calculus (which does not translate well over the internet) since velocity will be changing constantly due to negative acceleration.
none the less, if forward velocity is assumed positive, (and since mass is never negative) then momentum at any point in time where the car is in forward motion will also be positive. This means that applying a decelerative effect, the car will want to continue moving in a positive direction. Since we arent running on solid suspension, this give the sprung weight of the vehicle a tendency to roll forwards.
The only time you will get weight transfer to the rear due to braking, is if you have negative momentum. Ie) you must be travelling in reverse.
braking bias does not determine weight transfer, braking force does. Brake bias only serves as a means of determining the distribution of the braking force to the tires. This is all.
think about it for just a second. If you have a box of kleen-x resting on the back seat of your car and you pull the e-brake, doesnt it slide forward?
i think it does.
it wil only partially hop back after you have come to a complete stop and the vehicle returns to a neutral loading state
the reason that the weight transfer feels less pronounced (or is less pronounced, I should say) with the e-brake is because the braking force is not as strong. You are only using half the vehicles equipped brakes to bring it to a stop, and whats more, the rear tires are sliding throughout this braking - which is less efficient than if they were not. The deceleration from a given velocity to a lesser velocity takes longer with the e-brake, therefore the change in momentum over time is less, resulting in less tranferred weight.
The reason greater deceleration is realized (on most cars) with greater front distribution is because weight will naturally be loaded over the front tires during deceleration, thus increasing grip. If you experience understeer during the braking process it is because too much deceleration is being demanded of the front tires. They become overstressed and slip - steering acts as an additional stress on the front tires.
Moving the bias to the rear demands more of the deceleration to be generated by the rear tires. During deceleration, weight is transferred forward (as mentioned), so rear grip will already be disadvantaged (relative to a neutral loading scenario). With less grip available, braking force induces slip in the rear tires with relative ease. Couple this with some steering input (which you can now do since the front tires are responsible for less braking, leaving more grip available for turning), and the lateral forces induced break the lateral adhesion of the rear tires. TADA, we have oversteer. On a sidenote - this is the basis for a brake induced drift
the exact amount of weight transferred, and the required braking force to induce a state of slip in the rear tires is dependent upon several variables. Those within our control do not exclude vehicle mass, suspension settings, and tire compounds. So you may have to perfect these settings before attacking your brake bias. Elevation changes within the braking zones of the course you are running should also be brought into consideration.
end of story
for the record, this is exactly what i said way back in post #6, just expanded by about 200x
edit: perhaps not end of story
also for the record, it is possible to initiate slip at turn in with greater front brake bias. However, the car setup is trickier. The front must have enough avalaible grip to both brake and turn into the corner without initiating any understeer. If enough weight can be transferred forward without over stressing the front tires, then the rear tires may still break free under lateral loading.
This may be what you experienced with the skyline awdrifter2, especially with the stickier rubber.
It is entirely possible, but for many cars it is not probable.
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