Notch has now done about 500 miles since the brake upgrade so everything should be nicely seated to allow a proper brake test to be carried out.
Before moving on the the actual test I made some calculations regarding the smaller diameter pistons of the new EMPI calipers. The original ATE T3 caliper uses 42mm pistons while the EMPI - which is actually a copy of a Girling T1 caliper, uses 40mm pistons. 2mm less in diameter doesn't sound like much but it means 9.3% less force exerted onto the brake pads than the 42mm piston for the same force applied to the master cylinder. On paper this means that one would now have to push the brake pedal harder by a few kg's to generate the same force as the 42mm piston. It also means that the distribution of total force between the front & rear brakes changes by 2.8% toward the rear. As stated in an earlier post - I really can't feel any of this when driving the car - these brakes are a lot lighter and crisper than those on my Squareback which still has the original ATE calipers. Maybe its because the notch weighs less than the square...
![Huh? :huh:](./images/smilies/hum.gif)
On to the brake test. It was done at Safety Brake & Clutch in Randburg using a Bosch brake dynomometer. The machine expresses the braking effort in kg of each road wheel as a function of the incerease in torque on the motors driving the car's wheels as the brakes are applied. Maximum brake effort is achieved just prior to the brakes locking up and causing the wheels to slip on the rollers. Consequently the higher the weight on the axle being tested the higher the indicated maximum brake effort. In the case of a rear engine car where more weight is on the rear axle the rear brakes will therefore indicate a higher maximum brake effort than the front brakes. The opposite will occur when testing a front engine car. This simple test does not show whether the balance between the front and rear brakes is correct although this can be determined if a load cell is available to measure the actual force applied to the brake pedal. None of the brake shops I contacted have such a thing... Anyway, brake efficiency is calculated as the percentage of the total braking effort from all 4 wheels divided by the vehicle's test weight - which is the unladen weight plus that of the driver/technician doing the test.
Total brake effort in kg
----------------------------- x 100%
Vehicle test weight in kg
Figures for the notch are as follows:
645 kg
--------- x 100% = 63.24%
1020 kg
According to the technician who performed the test this figure is very good for a conventional non-assisted brake system and may even improve further as the pads/shoes bed in further. It also complies comfortably with UK MoT requirements.