Category Technical Talk

In this section, let’s take a look at one factor that determines the location of your car’s brake calipers.

First, we look at the front wheels. You may find many front-wheel-drive cars have their front brake calipers in front of the axle, that is because for FWD layout, the engine is usually transversely placed in front of the axle. With such layout, the steering arm can not be placed in front of the axle because the transversely placed engine acts like a wall to block the passage of the steering shaft. Therefore, the steering arm can only be located after the axle, which means there is no place left for the brake system at the same location...

Brake calipers are essential to your car’s ability to stop and are arguably one of the most important automobile brake parts. Some car’s brake calipers are in front of the wheel axle, while other cars have the brake calipers behind the axle.  For example:

– Toyota Camry, Honda Accord: front brake calipers in front of the axle; rear brake calipers behind the rear axle.

– BMW 2/3/4 series, Ford Mustang: front brake calipers behind the front axle; rear brake calipers in front of the rear axle.

– Porsche Cayenne, Infiniti G37: both the front and rear brake calipers are in front of the corresponding wheel axles.

– BMW 5/7-series, Audi A8, Mercedes-Benz S550: both the f...

In this section, we will take a look at the last type of automobile suspension, which is usually used for rear wheels.

In the H-arm system, one end of the arm is connecting to two locations of the car body; another end connects to two locations of the wheel hub. The H-arm alone can limit 4 degrees of freedom, so it need another horizontal control arm to limit one more degree to make the whole system with 1 degree of freedom.

However the above design has non-optimal wheel movement trajectory, most automaker will not use such design without modifications...

Now let’s take a look at the third type of automobile suspension: the MacPherson type system. For simplicity, you can consider the MacPherson suspension to be the double wishbone suspension with the upper A-arm replaced by a vertical strut, whose upper end is rigidly fixed to the car body’s strut tower.

In the following chart, the one highlighted as “Original” is the most original MacPherson suspension. Of course there are multiple variations...

Suspension Design: Double Wishbone

In part II we briefly analyze the first type of suspension: trailing arm. Now let’s take a look at the second major type: double wishbone suspension.

This type of suspension uses two “A” shape arms, one place on the top and the other in the bottom. Because each A arm can limit 2 degrees of freedom, so the two A arms together limits 4 out of the total 6 degrees of freedom. Therefore we still need one more restriction to make the whole system to be 1 degree of freedom.

For front wheels, the extra restriction is the steering arm; for rear wheels, car designers usually use a toe angle control arm.

In the below chart, the one labeled...