Older convertible vehicles can be prone to vibrations but when you also have brake pulsing, it may not just be the flexible body causing the issue. SureTrack community member wilhiteauto had an older Audi Cabriolet in the shop that had brake pulsation and a shimmy at highway speeds. The replaced all the brakes but still had the issue. They posed the question to the community, and with the help of fellow community member DAG1365 and others, they were able to resolve the issue quickly.
The following Community Fix summarizes the interaction between members of the community that led to the solution.
Vehicle
1994 Audi Cabriolet 2.8L
Title
Vibrations at low and highway speeds, turned new brake rotors.
Complaint
Customer complains of vibrations and pulsing of brakes.
Diagnostic Steps Performed/Parts Replaced
Test drove vehicle and at low speed you can feel the brake pedal kind of pulse, and at highway speeds you get a bad shimmy/vibration. Found bad tie rods and replaced. Inspected all other front end parts and could not find any noticeable problems. Pulled front rotors off and cleaned all mating surfaces and did not change problem. Also checked the balance of the tires and got them rebalanced. Also checked for out-of-round tires/wheels all are good. Replaced all brake parts including pads, rotors, hoses, calipers, and master cylinder. Still no change. Running out of ideas and looking for any other input.
Best Answer from Community Member DAG1365
Have you checked run out of rotors to make sure they are not out of round or need machining flat? Have you checked cradle/frame mounts, engine not moving (mounts), be sure ball joints and control arm bushings are good. Does system have ABS unit? If so, you may try to drive with ABS module unplugged.
Cause
Had the new rotors checked for run out on brake lathe and found that they needed to be turned to correct it.
Correction
Turned rotors on brake lathe to correct run out issue and vehicle vibrations and brake pulsing is gone.
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