It seems to me that GS front rotors need to be turned while on the car. Can someone verify this?

Here's my problem. I had my front OEM rotors turned when I replaced the pads with new OEM pads. Then, when I installed the disc and before putting on the wheel, by manually rotating the disc it will allow you to see that the rotor is not true/flat. You could see it waving on the edge by a tiny bit. To confirm the irregularity, I put a brake bottle on the floor right next to the disc as it slightly touches the top of the bottle cap. Rotating the disc allows you to see and hear that the disc contacts the bottle only in one area- so there is actually a warp.

So I thought it was the machine shop who did a bad job. I took the discs out again and brought it to another reputable shop. When I got it back, its the same story all over again. Driving the car in slow would make you hear the disc touching the pads in certain points like womp...womp...womp. I think I am at a point that I need to buy a new rotor but my curious mind won't let go of this. I've always done my brakes for more than 20 years and this is the first time I've had this problem.

 

The rotor needs to be firmly attached to the hub before you can do the test you mentioned. Normally, that happens when you put the wheel on and tighten the lug nuts. Did you use some spacers and lug nuts to pull the rotor up to the hub?

 

The rotor was firmly attached by putting on and tightening the bolts. I even sanded both mating surfaces to ensure that no dirt or foreign object is embedded and acting like a wedge.

The idea of having the rotors turned "on-board" came from a mechanic- not a Lexus mechanic. He said that some Japanese cars, especially some Honda Accords, are recommended to have discs turned. I need confirmation if such is the case with the Lexus GS.

 

If the GS rotors need to be turned on the car, it's not common knowledge. I know that some shops don't have the proper adaptors for all the rotors on the market, but I would be surprised if two shops can't set up a Toyota/Lexus rotor on their machines.

Can you mark the high spot relative to the hub, take off the rotor and put it back on with the high spot rotated 2 or 3 lug nut holes? See if the high spot follows the rotor or the hub. Sorry I can't be of more help.

 

I believe what you are describing is referred to as disk rotor "lateral runout". Common runout limits on Toyota vehicles is .004" (0.12mm) total. A little runout helps press back the pads from the rotors while driving. Excessive runout causes a pulsation in the brake pedal when slowly applied... Usually, runout decreases as the pads seat to the rotor; thus, truing the rotor..

Answering your "turning on the auto" or "on the car brake rotor turning" question... Lexus last turned mine on the car...
I'm attaching a link with a photo of the "machine"

http://www.brakeinfo.com/html/procutlathe.html

Call around, shops know about the machine your looking for.

Additionally, a Google search of "on car brake rotor turning machine" may provide additional references.

 

I will call around. The fact that Lexus last turned your rotors on the car reveals something. Thank you folks for your help. I will post an update here whatever happens next.

 

I did mark the high spot and rotated the disc forward 2 holes. The high spot followed! It did not make sense to me. But I can't think that 2 machine shops are faulty- I've used both of them for years!!!