Hi ya all!

Quick question as I saw this question posted online and there is quite the debate over it with two answers going back and forth. I have never done the job but I would like to know the answer for if I ever do.

The question is simply this: Is it normal for the brake disc (specifically the front one) to wobble when just removing the tire? Meaning let's say your just changing the tire, so you undo the lugs, take the tire off and that is all...but you are able to hold the disc and make it wobble back and forth?

Like I said, I have never taken a tire off my car (Jag X-Type) yet nor needed to fix brakes, but in my mind (I have done the job many times on previous cars) one would think there should NOT be any wobble or play with the disc since the piston should be expanded out in the caliper and the pads should be seated nicely against both sides of the disc (rotor). The only reason to me it should wobble is if the disc is warped or the pads are on their last legs. That is my "theory" on it.

However the counter theory is the wheel and lugs itself tighten everything up so the disc does not wiggle back and forth?

So which is the correct answer? Any thoughts....

peace out,
daddylogan

 

As I have done many time, the answer is: Yes, the pads hold the rotor nicely in between them but not tight and when the lug nuts and the tires are removed, there nothing hold the rotor tight to the hub, it will loose and wobble, but you can't remove the rotor without remove the bracket, caliper and the pads.

 

daddylogan, like Thanguar said, the rotor is just sandwiched between the rim and the hub assembly. So, with the tire/rim removed, the rotor will just float on the hub and wobble like you are seeing. The same it true for the rear wheels too. Most manufacturers have gone to this setup as it is a cheaper way of doing things. Also allows them to make parts that are more universal to fit over more product lines. that way, if they wanted to use the same hub on say a Corvette and a Camaro, all that needs to change is the rotor, not have to have a whole rotor/hub assembly for each car.

 

The tire lug nuts hold the brake rotor in place so once they are removed, in theory, the rotor will be loose. In my experience the rotors will be rusted onto the wheel hub so they need a good whack to break them loose. I see your point about the brake pads but they will be retracted slightly because no hub, bearing, or rotor is perfect so there is some runout which pushes the pads away from the rotors very slightly. Also the pads only constrain the rotor from axial movement, not radial. The rotors should be free to move a bit without lug nuts in place which is exactly why you need to put lug nuts back on to measure for warped rotors.

 

Good enough answers for me! Thanks guys. From my younger days of doing this job I guess I always remembered my disc being pretty sturdy...but maybe that was rust and the "stuck/weld" factor with mine? LOL

peace out,
daddylogan

 

daddylogan, this is one of the differences that has happened over the years. The older cars didn't have a driveshaft going to the front wheels. So, you simply had a spindle and the rotor housed the wheel bearing in it. The newer cars have a lot more moving parts there and to help simplify things repair wise, they separated the hub and rotor. Nothing like having to pull the rotor off and then put the rotor on top of a bunch of wood blocks to then start tapping the race out of the rotor. Those were the days.

 

Well, I'm old enough to remember the little "screw on washers" that had concave/convex shape with small slots from the lug bolt side out halfway from center to edge. They held the rotor snug when the wheel was removed. And some fun getting them off when they rusted in there good.

Then there was also on some, the rotor hold down bolt (1) that held the rotor snug.

 

The

 

 

Those metal washers aren't that bad. Granted, I tend to just grab them with a pair of needle nose pliers and break them off. Makes removal really easy. mainly there to help those on the assembly line. As for the bolts, never really ran across those in my years.

 

I just want to added a note: Volvo had the screw to hold the rotor in place with the hub, it be nice if every cars have that.

 

Why? Pray tell.