My 95 conv brakes dont have the stopping power that it should. I believe my rear brakes arn't working much at all. I installed rear pads on it last year, checked them recently and they look like new. I have read something about adjusting the rear brakes by using the parking brake? Also i read if it gets too bad you can adjust then with a small allen screw on the rear rotors. Any have any sugesstions? Thanks

 

You can adjust the rear brakes if you have drum brakes on the rear. There is a star wheel adjuster that is supposed to self adjust with the parking brake. I'm not familiar with the corvette setup on a 95, but a lot of cars that have rear disc brakes use a seperate parking brake shoe. Check and make sure that your caliper slides are clean and lubricated. Also make sure you don't have a hydraulic problem ie. dirty fluid or air in the lines.

 

On a car like the C4 the rear pads should last about 50% longer than the front pads. The fronts will do anywhere from 60%-80% of all the braking, depending on the rate of deceleration. If you look at the equations at the end of this post you'll see that the ratio is dictated by the lay-out of the car, not the size of the brakes.

What you want, is too have both the rear and the fronts reach "lock-up" at the exact same time under all circumstances. This is impossible without EBD (electronic brake distribution). Hence, the conservative nature of the rear brakes. You don't want the rears locking up prematurely.

Be VERY careful when it comes to making changes back there. Upgrading the rears to increase braking power, not just feel, can be a double-edged knife. More braking power to the rears will only do you well if;

1. the balance is woefully off and the rears are under-utilized, if you can lock-up the rears your already at full potential or

2. you have increased the weight the rear tires carry, the grip of the rear tires and/or minimized the weight transfer to the front.

Putting more powerful brakes on the rear alone do nothing more than cause you to lock up or go into an ABS event sooner. You must increase the rear tires load to benefit from an increase in the rear brakes power. Otherwise, the rears should be looked at only from a "feel" standpoint.

Basic "start-off" Equations for brake balance
Equations: (for ease and consistency try and use meters and kg)

NOTE: Equation 1 does not mean more weight you have more stopping force, it is just to calculate the stopping force required. As you can see in Equation 8, the larger the stopping force is the larger and more aggressive the brakes need to be or can be.

1.
stopping force total = weight of car * longitudinal coefficient of friction of tires

2.
Front Force = (weight front + total weight) * tire friction * height of CG * (1/wheel base)

3.
Rear Force = (total weight - rear weight) * tire friction * height of CG * (1/wheel base)

4.
% front = Front Force/Stopping Force

5.
% Rear = Rear Force/Stopping Force

6.
Area of Master Cylinder * pedal ratio = M
Area of front or rear piston= N
Mechanical Force Ratio= M/N

7.
mechanical force ratio front = mechanical force ratio * %front
mechanical force ratio rear = mechanical force ratio * %rear

8.
Stopping Force = pedal force * brake pad coefficient of friction * mechanical force ratio *
(1/radius of the tire) * brake rotor effective radius
.....solve for the parameter you need


As far as making the system (all disc-brake) more rear bias you can:

1. Install pads with higher friction
2. Larger rotor
3. Calipers with a larger piston

Or the most common is change the proportioning valve to increase the rear brake pressure cut-off. The proportioning valve only lets a certain portion of the pressure through to the rear wheels so that the front wheels apply more braking force. If the proportioning valve were set to 70 percent and the brake pressure were 1,000 pounds per square inch (psi) for the front brakes, the rear brakes would get only 700 psi in comparison to the fronts 1000psi.


Only you can decide for yourself if you need more rear brake. I just hope this info helps you in making an informed decision.

 

thanks for the replys.. has anyone ever heard of using the parking brake on later C4s adjusts the rear brakes? like backing up used to adjust the old drum brakes. I read this in one book. Then it said that if they are too far off.. then u have to take the rear caliper off and adjust a little allen screw. Well i did this yesterday and adjusting the allen screw does effect the parking brake and im not sure yet if it helped the actual rear brakes to work better. Im not trying to get these brakes to work any better than they was engineered to.. they just dont have the stopping power they should.. and the rear pads dont look they have worn a bit in the last year.. Thanks all

 

From what I read you must use the emergency brake 60 times before it will begin to adjust the rear brakes. If you dont know the history of the car I would start using the ebrake and see if it has noticable effect on your car.

Ray

 

I don't know of any rear caliper or front that's adjustable. The drum-in-hat parking brake is adjustable. But that's a seperate system.


I think you may be looking for this:

http://www.dougrippie.com/drm/brake_...eBias%20Spring