For the real techies out there !!

What is the nature of the resultant forces transferred from the caliper to the frame of the vehicle under heavy breaking?

Is it a function of the geometry of the suspension? If so, what are the key elements?

Does it matter if the caliper is mounted forward of rearward of the hub, or for that matter below the hub?

Specifically in a C5/C6 are the resultant forces under braking such that it causes front dive, front rise or squat (both front and rear dive), or perhaps the reverse of squat with both front and rear in rise?

Are these forces significant is real world track conditions?

 

My head hurts.

 

I would say that caliper placement is irrelevant. Front end is going to dive if only front brakes were applied, whole car would squat if only rear brakes were applied and somewhere in the middle when both are applied.
It has more to do with the brakes stopping the wheel rotating and said wheels placement on the body. If you stop the wheel and the tires hold, physics dictate that the remaining energy will try to rotate everything else around the hub.

 

A hint or a misdirection?

Think of the relationship between the centerline of the hub and the mounting points of the control arms. Won't the force transferred to the frame be a function of the relative distances from the hub centerline to each of the 4 mounting points?

 

Any car, not just a 'Vette increases the downward force on the front during braking. The harder you brake, the greater the downward force. The general feeling is that the weight of the car goes forward during braking and rearward during acceleration. The reaction of the caliper to the frame gets lost in this shuffle, and I think the previous poster is correct that the location of the caliper WRT the frame really does not matter. The reaction goes through the suspension then reacts with the fram at pivot points. This would remove any moment and convert it to a vertical focre to the frame. The frame should be very stiff with respect to the forces from braking. Otherwise, the fenders and other attachments would be cracked and distorted. What you try to control is the weight [inertia] of the car vs the traction of the tires. That and that alone determines whether you get to where you want.

 

rotor placement is not as critical as rotor diameter. a larger rotor has more leverage which transfers more stopping power to the suspension, and finally the frame. the corvette has quite a strong frame due to the hydroformed design of it. i have installed quite a few of the baer eradispeed two piece rotors on the c6 and the braking power picked up considerably. have you noticed the larger diameter rotors on the zr1? and the c6r race team cars? the other reason the larger diameter rotors work better is heat dissapation. remember, brakes change forward motion into heat. when you get rid of heat faster, you will stop quicker before fade comes into it. note the air ducts in the wheel wells of the c6.......

 

I've read that the engineers put the brake calipers towards the middle of the car to reduce rotational inertia. Simple physics states rotational inertia in minimized by moving the weight closer to the CG rather than away from it. This helps the car turn quicker.

Rather than look at the forces being transmitted through the suspension to the frame, look at the car as a whole. You've got a braking force applied at the contact point between the tire and the road. You've got a center of gravity (CG) several inches above the road. That means you're going to have a rotational torque on the car that's going to want to force the nose down and raise the rear up. The higher the CG and the harder the braking, the more the torque. The downward and upward deflections are going to be dependent on the spring rates and damping factors of the shocks.

This force is very significant at both track speeds and street speeds. Under hard braking, the front contact patch gets larger with more apparent weight on it while the rear gets smaller with less apparent weight. This increases the turning ability of the font tires and decrease the traction at the rear which can cause the back end to slide out. High Performance Driving schools will teach you to manage these reactions.

- Mark

 

hence, the smaller rear calipers so the rear braking does not out power the front causing handling problems.

 

Learned this on the old bicycle with f/r hand brakes. The front brake stops you and the rear brake keeps you in line.

Both work together for control in stopping.

 

The correct answer to this question will take a detailed suspension analysis -- way too involved for a forum post! The forces are considerable, that's for sure -- especially if using grippy tires.

The suspension geometry is part of it, but the key elements are front/rear static weight, height of the center of gravity (CG) and wheelbase. Actual suspension arm geometry affects how much of the total load is transmitted by each member.

Caliper location will not change the torque reaction into the chassis members, but it does play a role in overall CG (F1 cars mount the calipers practically at the bottom) and steering rack location. There are some minor benefits to certain locations relative to forces, but that analysis is usually reserved for top-level racing cars.

The front will always dive and the rear will rise. Certain geometric arrangements can reduce this (front anti-dive and rear anti-lift), but too much of that stuff causes other problems that are much more difficult to resolve.

Yes.

Chris