1. Verify that the joint shaft is not twisted or cracked.
2. Turn the joint shaft by hand and verify that the bearing rotates smoothly and freely.

Drive shaft
Joint shaft removal/installationMazda 6 Service Manual: Replacing a Tire
WARNING
Always use tires that are in good condition: Driving with worn tires
is dangerous. Reduced braking, steering, and traction could result in an accident.
Replace all four tires at the same time: Replacing just one tire
is dangerous. It could cause poor handling and poor braking resulting ...
Mazda 6 Service Manual: Power brake unit inspection
Warning
The following inspection methods are the simple inspection methods
to judge the function of power brake.
If there is malfunction in power brake unit, replace the power
brake unit as a component.
Power Brake Unit Function Check (Simple Method)
Step 1
1. With the engine stoppe ...