Vibration during braking


mtup
10-06-2012, 12:52 PM
My daughters g5 has a vibration issue on the left front when braking from 40mph and up. I have inspected everything on both front sides and can find nothing wrong including ball joints, tie rod ends, rotor, sway bar, loose struts. The only thing I found is her LF strut leaking. I checked for slack by turning the wheels with and without a load on the front end and it is tight as can be. No slack or movement up and down either Her car just turned to 100,000 miles. Any ideas?

gmtech1
10-06-2012, 02:09 PM
Vibration when braking is usually a warped rotor issue. What kind of shape are the brake pads in? You may want to replace the pads and either have the rotors resurfaced, if they are thick enough, or just replaced the rotors. Aftermarket rotors are fairly inexpensive for these cars.

mtup
10-06-2012, 02:15 PM
Thanks tech. I took the caliper off, put the car in neutral, put two lug nuts on to hold the rotor and spun it using a screwdriver as a dial indicator. The rotor was perfect while holding the screwdriver probably .010 away. Could stabilizer bushings cause this?

gmtech1
10-06-2012, 02:24 PM
No, the link will not cause this. Brake pulsations can be caused be a rotor being .004" of a inch out. Not something you would be able to see with a screwdriver. This is made worse when the rotor get some heat built up in it.

Tech II
10-06-2012, 09:05 PM
GM Tech1, I thought max rotor run out was 0.002?

gmtech1
10-06-2012, 09:09 PM
Tech II, you are correct! Thanks for the catch!

mtup
10-07-2012, 08:53 AM
Actually, there was no runout. I used the .010 to illustrate how close the end of my screwdriver was. My first thought was the rotor until I drove the car. I forget to mention that the steering wheel vibrates back and forth when braking from higher speeds and there is no pulsating brake pedal. The vibration is on the left front. After I put the wheel back on and drove it again to maybe get another idea what it was, it was better and the vibration was much less. My daughter drove it to do her daily running and came back and told me it was better. Now I am suspecting lower control arm bushings. Is this a problem in these cars? Looking at them, they look fine.

Tech II
10-07-2012, 10:42 AM
My money is still on the rotor......

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