Scarmiglio

O.K. but follow me for a second. When you brake in a normal car (or truck), there is some nose dive. This shifts the weight (and center of gravity) down over the front wheels and off of the rear wheels. A car with a stiff suspension doesn't nose dive nearly as much, and therefore the rear wheels have more weight over them, and can better participate in braking.

I'm not stating this as fact, it's just how it has been explained to me.

B8 Turbo

I would say from actual personal experience that the stiffness of the spring rates, especially front, do play a part (maybe not astronomical) to braking due to the CG of weight transfer. I previously had stock shocks & springs. Whenever I do hard or sudden braking, the nose dive adds another forward motion and I felt really insecure by the softness. Then I switched to coil-overs, the feeling is more secured. Before the switch, I had replaced a leaky master brake pump, SS brake lines, fresh rotors, and better-than-stock-pads, the feeling is still dictated by the nose dive. I guess spring rates still plays an important role.
Unlike some of y'all, I don't have sources or numbers to back it up. This is based on my what happened to me and my tendency to blame it on worn parts like the shocks!

carguycw

You are confusing cause and effect. The weight transfer causes the suspension to compress, not the other way around.

Scarmiglio

Not really. The stiffness of the suspension has a major impact on how much of an effect is caused.

carguycw

No, it does not. You are equating nose dive with weight transfer; they are not the same, nose dive is a *consequence* of weight transfer.

Here is an illustration: Picture two 8' long planks sticking out from a platform. One is made of 2" thick wood. The other is made of 6" thick steel. When you walk out to the end of each plank, the wood plank will bend a LOT more. However, your weight is constant, and the length of each plank is the same. Therefore, the force you exert on the end of each plank is equal. The wood plank bends because it's not as stiff as the steel plank; it's NOT because you weigh more or exert more leverage when you're standing on the wood plank.

The situation when a car brakes is the same. The force exerted on the front and rear wheels is a function of the mass and physical dimensions of the vehicle and the rate of deceleration. The stiffness of the suspension is a CONSEQUENCE of the weight transfer. The same amount of weight transfer will occur regardless of the suspension stiffness.

There's one small catch to this: the center of gravity of a vehicle will shift slightly forward when the nose dives; however, the shift will be VERY small on a car with a low center of gravity and relatively long wheelbase, like a Protege. It will only make a big difference on a vehicle with a short wheelbase and a high center of gravity, such as a jacked-up Jeep, a motorcycle, or a mountain bike with front suspension.

Scarmiglio

OK, that makes sense. So, in effect, a better suspension makes the car feel more controlled under braking, but doesn't really improve braking (at least, not much)?

Rando

OK i'am a newby here but the stiffiness of the supension DOSE make a diffrant in braking or turning. Lets look at it this way. A flat pice of metal siting on four points at each corner will have a equal amount of weight on all four points. now angle the metal up on one of the points and the weight shift the the oppist cornner. Now on a car the weight moved to one tire will alow for more traction and les traction on the oppist cornner. That is why you have atiroll bars and use weight jacking the try to keep a car in a nomal state during cornning. It is not the brake itself but the add weight or down frorce that will help the tire to have more traction. The stiffer supension will help the car from shifting the weight and distrubuted to all four corner thus will have all four tire to have and more equal amount of traction.

Rando

BTW I love these food fights. This is what make this forum on of the best i seen. and glad to be on it.

carguycw

It can have a large effect, but it's because of reduced camber change during braking, not because of weight transfer. Reread my original post on the topic.

Rando

Sory, after I read my post i don't think i made it clear, but here is the just of it. Stiffier supension help control the weight transfer wich will help to keep all four tire on the ground with more even traction and help to keep the back wheels from looking up.

carguycw

NO. Reread my earlier posts. The stiffness of the suspension has ALMOST NOTHING to do with the amount of forward weight transfer! Nose dive is just a CONSEQUENCE of weight transfer. It does not change the AMOUNT of weight transfer.

Your illustration shows what happens when you move the center of gravity, which basically does not apply to braking. When the nose dives, the center of gravity shifts *slightly* with reference to the wheels, but not enough to have a measurable effect on traction. ALMOST ALL of the traction change when the nose dives is due to camber change when the suspension compresses!

The story is the same during cornering. The total amount of lateral weight transfer is a function of the car's mass, the vertical and horizontal location of the center of gravity, and its track width- the same as the equation for braking, except applied sideways. Fancy that. Playing with spring and swaybar stiffness will change how much of that weight transfer occurs at each end of the car, but the TOTAL weight transfer DOES NOT CHANGE.

Rando

[QUOTE]Originally posted by carguycw
[B]

Playing with spring and swaybar stiffness will change how much of that weight transfer occurs at each end of the car




less weight on a tire = less traction
less traction = less braking power for that wheel

carguycw

One other thing to add to muddy the waters...

Although the stiffness of the suspension has almost zero effect on braking (as I've already explained), lowering the ride hieght WILL improve the potential braking power of a FWD car. The closer the center of gravity is to the ground, the less forward weight transfer occurs, distributing the braking power more evenly between the front and rear wheels (the front wheels are overloaded on FWD cars, wihch hurts braking).

To clarify, the suspension does have an effect on braking, but only due to ride height, NOT stiffness.

carguycw

When you are CORNERING. I was talking about changing the suspension stiffness and distributing the weight from front to rear WHEN TURNING. When you brake, the stiffness and geometry of the left and right sides is the same unless you are using really strange suspension settings. When we are talking about weight transfer forwards and backwards, stiffness is irrelevant.

Let me rehash...

When braking or accelerating, the force exerted on the front and rear wheels is a function of the mass and physical dimensions of the vehicle and the rate of deceleration ONLY.

Rando

I think that you might be geting weight transfer mix up with garvity pull (Gs) or inertia. if you have car swith no supension, there will be no weight transfer. Weight transfer can only be done if you chang the hight on a conner. You can not chage the inertia of a object unless you change the mass or speed.