ArandA4

<center><img src="http://pictureposter.audiworld.com/37389/rotor_runout.jpg"></center><p>So I was getting this vibration during braking at about 35 mph and this was on newly turned rotors. We measured the rotors after turning and they were pretty true so I suspected the hub had some runout.

Went to Harbor freight and bought a dial indicator and multi position base. Hooked it all up and set the magnetic base on the upper portion of the wheel bearing housing.

A couple things on the setup:

1. Since the rotor is held on by the wheel and lug bolts, I bought some 3/4" nuts to prevent the lug bolts from going through the rotor and hub and hitting anything on the back side.

2. I removed the brake caliper just to make sure rotor and hub could turn easily. Probably not necessary, but easy enough since the caliper is held on by two guide pins.

3. It's probably not too crucial to get the dial indicator truly normal to the rotor surface because I was just trying to index the rotor to minimize runout. Still, the more normal (perpendicular) the better.

So I measured the passenger side front and got close to .008 of runout. Many say that you can feel pulsation with anything above .001 or .002. After measuring, I'd remove the three bolts holding the rotor to the hub and rotate the rotor to the next hole position and repeat. Got the runout down to between .002 and .003.

On the driver side, runout ranged from .002 to .003 for all positions.

After test driving following all this, I have to say the pulsation is pretty much gone. Still, this little exercise showed me there's probably something going wrong with my passenger side hub/bearing. I'll deal with it in time, but for now I'm happy with this cheap DIY job.

<a href="http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=623">Dial Indicator</a>

<a href="http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=5646">Multi-Position Magnetic Base</a>

washburn33

Audi doesn't recommend turning rotors

quattrofrog

Duhhh and stock ones are $90 each. Expensive by design if you ask me.

ECS Tuning-Tom

Brand new either Brembo or Jurid, both of which are equal if not better than OEM units<ul><li><a href="http://www.ecstuning.com/stage/edpd/pagebuild_v2.cgi?make=Audi&amp;category=Braking&am p;model=B5%20A4&amp;submodel=Quattro&amp;engine=1. 8T">A4 1.8TQ Brake Page</a></li></ul>

Ram@S4-MTM

They match rotors on the car to match the hub exactly.<ul><li><a href="http://www.procutinternational.com/index.html?html/awards/release08061999b.html~mainFrame">Pro cut on-car lathe</a></li></ul>

birdsong

Any reason other than they want the money for new ones?