Brake Rotor Runout Measuring
 

I replaced my front rotors over the weekend because I have had issues with brake vibration during previous track days. When I looked in the FSM for the torque specs I saw where they recommend testing the mounted rotor runout and adjusting the rotor position on the hub to find the position with the least runout. I didn't have tools to measure runout but now I feel like I should especially since I have the sport brakes with fixed calipers and 14" rotors.

Before I go down the rabbit hole on this, any suggestions on which dial gauge and mount to get? I have seen in other threads where people mention testing runout but no details.

Per the 2012 FSM maximum runout measured on vehicle for both sport and non-sport brakes is:
Front .0014in, .035mm
Rear .0022in, .055mm


I used the Centric 125.42100 rotors and didn't have any vibration on the test drive but I want to verify runout.

I've always had good luck with Starrett gauges.

I use a magnetic base dial indicator and a heavy iron vise.

The vice sits in the floor, and wont move easily since its 30 lbs.

I then stick the magnetic base to the vise and orient the indicator to the rotor.

In the photo, I am checking tire run out, because the car had a shimmy in the steering.

Tire was 1/4” out of round.

So, you get the idea ..

Top of the gauges are Starrett, Brown & Sharp. Which I have both, plus a cheaper CDI. All are 1 inch travel. You can get cheaper gauges that won't break the bank. A good way to measure rotor run out. Remove the tire, remove the rotor. Clean the mating surface of the hub and rotor to remove any dirt, etc. Install the rotor and lugs. Torque the lug nuts. The best place to mount the gauge base is on the steering knuckle. But because it's aluminum. You have to clamp it into place. Can't use a magnet base. You can get the gauge at AutoZone, Advanced Auto etc.

Google

https://www.google.com/search?q=meas...hrome&ie=UTF-8

I'm going to go by Harbor Freight and pick one of these to try out. Can always return it if it doesn't work for me.

clamping dial indicator

Or this

machinists dial indicator

magnetic base

So I bought the clamping dial indicator from Harbor Freight and measured the runout on my new front rotors. I used a feeler gauge to validate the dial indicator. My thinnest feeler gauge was .002" and the dial indicator read .002".

Max runout is .0014" which is not much. I was just over .001 on my passenger side and .002 on the divers side. I pulled the divers side rotor and changed positions with respect to the hub a few times and got it down close to .001".

I wish I had the dial indicator before I pulled my old rotors off so I could have measured the runout on them because I did have some brake vibration on the track that I do not think was a pad bedding issue.

For people who have measured their runout after having brake vibration, how much runout did you have?

You might be breaking new ground asking for rotor run-out. Not much out there.

I will keep measuring the front runout when I have the wheels off since it only takes a few minutes.

I went to replace my rear rotors and measured the runout of the old ones and they were both around .001". Well below the .0022" limit for the rear. They have very little wear and no visible cracking so I left them on and didn't change them.