Brake shake with freshly machined rotors?

Torquing wheel nuts? How? Not from my experience. I've worked on quite a few different vehicles over the years, used both impact and wrench. Not seen a warpped rotor yet. Have had a few rotors pulsing but it always was improperly machined rotors. Use a micrometer and check the thickness around the diameter. Improper torque on wheel nuts will cost you a stud sometimes though .

I also think they should be washed. Soap and water would be fine, or methylalcohol as in spray brake cleaners. I suspect that most manufacturers apply some sort of filming corrosion inhitor to reduce the rusting of shelf stock, and if so that should probably be removed.

It happens, I assure you, and have seen, and been, a victim of it. None of the local tire shops here even have a torque wrench. When I have to use them, I carry mine along and torque the studs myself.

What kind of vehicle? Never seen it happen. I'd like to know how. I've seen wheels with stud broken off. No problem. Now that's difference in torque.

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

Here's my problem with that... it seems to be very anecdotal. I have seen the same kind of problems on properly torqued wheels. My experience with tire shops is very different from yours, though I do not question yours. Mine is that they all use torque wrenches these days, and it has been years since I saw a tech hammer a lug nut on with an impact.

My experiences are that rotors can be of low quality today - especially the budget rotors, and it does not take any amount of heat to warp them. Torqued lug nuts or not, they warp. I've also convinced myself that the cheap pads add to heat in the rotor and that ceramics do a much better job of dissipating that heat, thus reducing warping. I've used both semi-metallic and ceramics on the same model of rotor, and found a distinct difference between rotor anomalies with ceramics.

Contrary to that, I have also gone the route of meticulously torquing lugs, to find no notable difference between torqued lug nuts and those that weren't torqued.

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

The "requirement" for a torque wrench came along with the popularity of alloy wheels. Rattling lug nuts on with an impact was considered to be unhealthy for the alloy wheel. I've heard of cases of broken wheels, but I've never seen one. I believe it might be much easier to create an oblong hole in an alloy wheel than to break the wheel.

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.

Rotors WERE beefier a few years ago, no doubt. I agree my observations are anecdotal, but they have added up to some pretty firm evidence (not proof, but evidence).

One of the Dodge van I personally experienced, a national tire chain installed new tires for me and in about a month the judder was there. Nothing before that. DT had used the torque stix.

I pulled the rotors, had them machined true, and reinstalled them along with new pads. Ran for two years that way with no problem whatsoever. Then back to the same tire chain and -guess what - within a few weeks the pulsation and judder was back. (Cause and effect thinking starts here.)

After than, I adopted the torque wrench only policy and have had no more problems.

I live in a small town. In a larger town, people have seen a torque wrench. Here, they dont have them at all in the tire shops, etc. And the warpage goes on. We had another car, a Buick, that suffered the same problems after new tires were mounted, whereas it had none before....it is was NOT a tire problem.

I have a long list of them. For me, it doesnt take but a few seconds longer to torque the studs, star pattern.

Anyone who wants to ram them on with an impact wrench, go ahead. (I have an impact wrench and use it for some front end work but not for tires. I am not that lazy.) I am convinced it is not to my best interest.

Oh one more thing, in all the cases I have noted, the judder does not occur immediately. It starts days to weeks after the action (new tires, pad replacement, rotation) which I believe initiates it. This, in my mind, supports warpage with heating of the rotor.

If you read the Babcox reports, they mention the problems of hub runout and thickness variation. If that were the cause in these cases, one would notice the shudder immediately. Thickness variation may be corrected by machining the disc, but hub runout wont be - unless the rotors are machined on the car.

And further they mention the possibility of shimming the rotor/hub, or even indexing the rotor with respect to the hub irregularity, to minimize this problem.

It is an interesting subject and, again, you can do what you want (but not on my cars ;>)

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:

I agree with this observation. I have concluded it to be related to semi-metalic pads, as I don't see that now that I've switched everything over to ceramics. I've also upgraded rotors that I use, but even with the upgraded rotors, I found the problem could occur (only not as regularly) with semi-metalics.