Kirk930

Well, the verdict is in.........warped rotor, or really badly machined......bought a dial indicator and it's all over the place as the disc rotates......up to .006"

I measured the other rotor and less than .0015 variation from high to low. From a baseline there was a fluctuation of about +/- .00075"

How would a warped hub show in this case? I'm assuming there is no problem with the hub because there was no pulsation before.

I'll exchange it tomorrow and we'll see.

I could probably change rotors blindfolded by now!

69gaugeman

You can put the dial indicator on the hub itself and rotate it. You must remember that any runout on the hub is multiplied due to the distance to the brake pad surface.



You can mark the high spot on the rotor and the bolt on the hub. move the rotor one bolt hole and notice if the high spot moves with the rotor or stays at the bolt marked on the hub. If it follows the rotor, then the rotor is the problem. If it stays with the bolt then it is the hub. If the total amount of runout changes as you move around the bolt holes, then it is a combination of both. If that is the case you might be able to match up the low on the hub and hign on the rotor to get to zero.

Also note that if you feel you need to have the rotor machined, if you may be able to just have the hat faces machined to the brake surfaces. Just make sure they do not take off more than .005 or .006" and that they do the hub mounting face and the wheel mounting face of the hat. (it is easier to do for some machine shops and vibration is much less of an issue)

69gaugeman

I just realized you are in burlington. If you would like I could stop by and take a look with you. ( I am in Guelph Monday to Friday)

Kirk930

Rod,

I may take you up on your offer if I still have a problem with the new rotor. Hopefully they have one in stock today.

I'll let you know how I make out.

Thanks!

Kirk930

Installed the new rotor, triple checked everything, and threw the dial indicator on.........same problem.......same runout .005 max

Drove the car and sure enough, pull to the right without braking, and pulsation under braking.

Warped hub or bad bearing install???

I'm contemplating professional help......I hate to admit defeat, but I only have so much free time to waste!

69gaugeman

My offer is still on the table. I will be in Windsor today and tomorrow. Call my cell if you want help. 519.567.7019

Most likely a hub issue.

The pull to the right though indicates a caliper or alignment issue. We can check that all out.

Kirk930

Could the pull not be caused by the rotor/hub runout......from drag on the right wheel?

911rudy

Did you check the hub as Rod explained? Also make sure there is not some foreign matter between the rotor and the hub like and old washer or piece of gravel. When you turn the rotor mounted on the hub is the seam between the two symetrical all the way around? This would tell you at once if there was any thing between the two. Also, when you rotate the hub by hand is there any difference in feel as you turn it. This would indicate a bearing problem and could account for the pulling. Try rotating the other side and see if there is a big difference between the two. One last thing is to layout a grid from rear wheel to front with the steering wheel neutral and then check the measurement from the rear to the rear of the other front tire and then check the same for the front edge of the front tires. This will give you a rough estimate to see if there has been a pot-hole-from-hell encounter with one of the wheels. Good luck.

Kirk930

I made sure there was nothing on the mating surfaces. I even sanded the very slight surface corrosion off of the hub mounting points. The seam appears symetrical. Rotating the hub with pads removed feels uniform. The other side rotates much the same.

The thing is, there was no pulsation prior to changing the rotors. After changing the rotors the pulsation/pull appeared. I then changed the bearings (which I had planned on doing anyway) and same problem. If the hub was warped would it not have shown up before the rotor change??

I have not tried changing the mounting of the rotor on the hub and taking measurements yet as explained by Rod. I've spoken to my mechanic (who is within walking distance to my office) and he will take a look at it later this week, possibly later today.

69gaugeman

I have seen people machine the rotors while mounted. This would explain that issue. Do you still have the old rotors? You could replace them and measure it up to see what they show.

Kirk930

Rod,

I still have the old rotors. I was planning on having them machined as a "backup" set.

I had the car into Refined Motorsports yesterday. The rotors were both checked, and the right side completely disassembled twice. The rotor was mounted 180 degress different on the hub to see if there was any change. There is still a pulsation (seems a little better) and the tech is puzzled - might be the hub.

I'm not really sure how much time he spent on it as it looked quite busy in there.

69gaugeman

Just let me know if you want to spend some time on it. Give me a day's notice and I will bring some tools that will allow us to check out every thing.

69gaugeman

Any word on the brakes? Has it been resolved?

Kirk930

Hi Rod,

No, the brakes still have the pulsation..........I haven't had any time lately to mess with it more. I've just been living with it.........not very confidence inspiring though.........

Would a warped hub/improperly seated bearing not show as a vibration when driving without braking. If so, then it must be the rotor again...........maybe I got two warped ones??? Doubtful though.

I've since replaced the rears too.

PorscheMD

Is it possible that you got the washer for the mounting bolt that secures the caliper to the hub and the spacer that goes in between the calipaer and the hub mixed up? I believe they are different thicknesses which would cause the caliper to be offset in relation to the rotor which in turn would cause the inner pad to drag and cause a pull.