Tires with unequal contact and grip on the road cause unequal braking. Make sure the inflation and tread pattern of the right and left tires is about equal.
When the vehicle has unequal loading, the most heavily loaded wheels require more braking force than the others.
Loose front wheel bearings permit the rotor to tilt and to have poor contact with the linings. This causes eratic braking. Refer to Wheel Bearing Adjustment in Front Suspension.
Misalignment of the front end, particularly camber and caster, causes the brakes to pull to one side. Refer to Wheel Alignment Specifications in Wheel Alignment.