Brake shake with freshly machined rotors?

What?

Ive seen it happen on lots of different types of vehicles. To name a few I have seen recently, Chevrolet truck, Chevrolet Impala, Toyota SUV, Dodge full size van, etc etc.

None of these cars had any judder until locals fitted new tires or rotated tires, and hammered on the lug nuts with an impact wrench. The judder came on days to a few weeks after the work, and were cured by machining the wobble out of them. I think heating of the discs which are unevenly torqued down induces the distortion.

Whatever happens it is real, and it is avoidable.

I'm going to call you on that. Take a look at your rotor and hub. That hub is SOLID. It has to be since it houses the bearings. Now the hub goes over top followed by the wheel. Against a machined surface of the hub. Even with two opposing bolts the rotor has to run true to the hub. How can it possibly warp a rotor?

I'll keep doing all my own tire repairs and machining rotors. I've never bothered with a torque wrench. My impact would never break a stud and I have a pretty good idea what torque I'm getting if I do them by hand. I just finished correcting a poorly machined rotor on my dad's car that was done by a local shop. It was out by several thousands on the diameter. I have my own lathe. Set it up with dial gauge on inside and machined the other to match. Back on the Lumina, test drive and vibration gone.

The reason I understand that shops use a torque wrench is they don't want a broken stud and it removes the guess work out. Any jockey can do the job then and the shop isn't libel

There are internal stresses in rotors, and rotors themselves are of different designs. The ones I've seen are hollow between the sides for cooling/weight purposes. I can imagine that uneven stress on the center can affect the outlying metal. Too many people report bad torquing causes rotor distortion for me not to believe it happens. Like you I don't bother torquing when I change tires. Never have. And the only time I had a warped rotor was right after I ran hot brakes through a deep puddle. I think some rotors aren't affected by lugnut torquing, and others are. Best not to find out which are which.. But I'll probably continue to roll the dice if the rotors are cheap.

--Vic

Yes and heat I will believe. It could drive the rotor to wobble enough that the pads can't follow. But that would take a fair amount of heat to warp a hunk of steel that heavy.

Baloney. I'd like to know how many wheels I've done over the years. I'm not running a shop by any means but I've done a lot of work on vehicles and machinery. I'll argue to the cows come home on this one. Heat sure, but that's an entirely different matter.

They can believe it they wish. Old wives tale. I don't. Suspect it's any easy way to convince people to replace with new. Anyone without real experience with the tools can't argue. And the shop is clear. And that's the most important part for a shop. You can't offend a customer with new parts.

Ah ok. I'll buy that. I don't feel it's absolutely necessary but no harm in taking a few extra minutes. I've heard bikers say they won't touch their alloy rims personally for fear of damaging the metal which could lead to fracture later on. Seems a bit of a streatch but I'm no biker and losing 50% of your rubber at highway speed doesn't have a lot of appeal to me.

It's more fun to argue about brake system flushes and how brake fluid is constantly sucking up water until your MC starts overflowing.

--Vic

lol

You can do what you want. I am telling you what I have found, and you can take it or leave it. No hard feelings.

I hope you're being facetious. Otherwise I call BS.

Another Bad one for warped rotors from air hammers is Chrysler Jeep products, they warp bad and easy.

Mike

2000 Cherokee Sport 86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00 'New' frame and everything else in '09. Some Canadian Bush Trip and Build Photos:

Discuss your situation with a *quality* shop and go from there.

If you take your car in and ask them to machine the rotors and they dont ask you why, never go there again! A *good* shop will ask a ton of questions before service to determine what will fix your car, and a *good* tech take the

75 or 80 seconds it takes to toss a mag base on before he tears it down.

Finding a brake shimmy is auto shop 101 freshman year. Dial indicator on the rotor, hub if necessary.

So many shops and customers are their own worst enemies...

HTH Ben

Also... there is a tsb that says that rotor runout must be .002 or less... Sounds like an on-the-car brake lathe would be best...

TSB # is 00-05-22-002L

HTH, Ben

Wow... This post sums up the sorry state of the industry quite well...

I agree, in my particular case I am limited to two shops, if I take it anywhere else I pay out of pocket. just wanted to post to see if anyone had any other things to check just out of curiosity.

I will see if I can take it back on Wed. while I am in a meeting at the office...

nate

Somebody needs to give me the theory behind this phenonomon. The rim itself has nothing to do with it. The only device which comes into contact with the rotor is the caliper and pads. The piston side of the caliper should move with fairly little pressure so scratch that idea. The whole caliper should move if there were pressure on the outer side. Besides it would take a fair amount of pressure to bend the rotor. Only if the rotor were loose and something got behind to cause wobble after tightening then yes. The run out of the rotor would wear the rotor surfaces on opposite sides and opposite diameters, with consequent uneven thickness. Most of the rotors take some effort to remove after a few years of service so I don't see tire service causing problems. Finding a hub improperly machined from the factory is very unlikely given today's manufacturing standards. Removing a rim for tire service is not going to change the dynamics of the rotor.

Somebody has to show me an actual case before I'll buy it. I've been around too long.

It has everything to do with 'it'... Remember, this is with alloy wheels, not steel ones. There's a reason: steel rims are rather flexible, alloy ones are not, the center hub is much more rigid.

Oh, not in 99% of the vehicles on the road. Almost all have the rotor sandwiched between the rim and the hub. Check yours, and you'll see it. Exceptions are very exotic ones such as the Hummer H1 (inboard brakes on all for corners), the vette, some Jaugar models, and some high-end sports cars. Most common vehicles have rotors sandwiched just as described.

Humm...

Virtually everything above is either outright wrong, or misstated.

How long you have been around is insignificant if you stopped learning at 15. But, hell, in your world everyone else is wrong and you are right.

OK so how does a rim affect the rotor in either case? As you state most are sandwiched between. Forget exotic vehicles. How many of us drive such things anyway?

I know that.

You don't say WHAT's wrong.

On any of the common wheels most of us drive I've not seen it yet.

I've had it happen to an ordinary audi with alloy wheels about 15 years ago. I had new tires installed and the shop had hammered the wheels back apparently on full blast with the impact wrench, and I had a terrible shimmy.

I tried to torque the wheels properly at home, but could not get the bolts on one of the wheels loose. I cracked a socket trying to undo the bolts.

I went back to the shop and with the long hose they had on the IW they could not get the bolts loose without waiting for the compressor to build full pressure in the tank. When they torqued the wheel properly the shimmy was gone.

I always hand torque the wheels after this and I have never had a problem with it again.