| > Where does the warpage come from? You're sandwiching steel between
| > There is nothing to give or bend.
| They can both bend.
| When you tighten a lugnut to 100 ftlbs, it can apply thousands of PSI
| to the rotor/hub, more if using an impact wrench.
| Steel, cast iron etc all bend easily under such forces.
The torque applied to the lug nuts does not have to bend /warp the
rotor. All it has to do is apply uneven pressure to the rotor. After
that heat will finish the job much the same as heating a metal plate or
rod while applying pressure to it. With the materials they are using
today it doesn't take a bunch of panic stops to do it. Heavy traffic,
coupled with the driver riding the brakes could well cause the problem.
My Safari started showing signs of warpage after the first aftermarkrt
brake job. I think I will buy all new OEM parts and do the job myself.
New rotors, drums, pads and shoes.
The only foundation of a free Constitution, is pure Virtue, and if this
cannot be inspired into our People, in a great Measure, than they have
You are sandwiching aluminum between steel. My guess is that the hub
flange gets warped when the studs or threaded holes are pulled with
excessive force into the fairly soft aluminum. The aluminum between
the holes does no bend and thus the flange, and rotor warps slightly.
Steel rims are not susceptible to this as it is much softer between
The studs/hub flange/rotor is steel. On that you put an (soft)
aluminum rim, which often has a solid flange, and you clamp that with
I think an analogy is if you put a flat sponge on a table and a flat
piece of (printer) paper on top of that. Now spread your fingers and
push them down against the paper. Watch what happens to the paper as
you increase the force. The rim is made of soft material like the
If the clamping force against the rim had been even, instead of
concentrated around the bolt, this would not be a problem. The flanges
would not deform.
Got it - sorry for being slow. If the difference in torque was very
dramatic from one stud to another, or more so, if one stud was dramatically
tighter than all of the rest, then I could see a problem. Not so much with
the more minor differences being spoken of here. Plus - you don't have a
sponge, as in your analogy. You have a steel rotor. Mounted to that is an
alloy wheel. Both have more rigidity than your analogy. Reasonably
tightened lug nuts aren't going to present the same kind of pressure that
your analogy suggest, against a very flexible material.
Right, keyword is "reasonably". I have seen them go from just over finger
I wont argue the issue, but will continue to do what I do, as I believe it
to be overly nit-picky than rambunctious with wrench. I have seen it
many times, and that is good enough for me.
Uneven clamping forces in the assembly, along with the natural stretch
of fasteners, along with the thermocycling (especially extreme changes
like water puddle quenching or pad bake at the end of a really long
stop and mashing the pedal down for a long time, which causes localized
hot spots and pad material transfer). The three things you can control
as a driver are 1) driving through less puddle with smoking hot brakes
2) not holding the pedal down hard after a long hot stop - creep a few
inches a couple times and lightly hold the brake pedal instead 3) torque
your own wheels to spec. The only thing a tech can do for your car is #3.
I do believe you could also perform #4 on a horse.
I've found that if an automotive engine is missing, it's usually due to an
ignition problem, such as old plug wires or a weak coil. Conversely, if a
horse is missing the trouble is often in the fuel system. Try administering
additional oats, perhaps augmented by a few carrots and sugar cubes.
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
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
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
and judder was back. (Cause and effect thinking starts here.)
After than, I adopted the torque wrench only policy and have had no more
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
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
rotation) which I believe initiates it. This, in my mind, supports warpage
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
It is an interesting subject and, again, you can do what you want (but not
my cars ;>)
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)
There could be hard spots on the rotors. And perhaps while it was
sitting the area where the calipers were that did not rust is now
either harder or softer then the rest of it from that, although I
would not give that high odds. I had a impala back in the 70's that
did what you were describing and they only fix that worked was new
Just a suggestion: when you take a car in for warranty work, never
ever tell them 'how' to fix it. When you suggest a repair technique,
that is what the do, nothing else, because that is what you asked for.
Instead, give them the symptoms, make sure they can duplicate these
symptions and say: "Fix it, warranty". Heck, even if it is not
warranty, don't suggest how to repair a fault! People make this
mistake over and over--the shop must do what you suggest even if they
know it won't fix the problem, and they cannot fix anything else
because you asked for a specific action to be performed.
Never assume. Let the shop/mechanic find teh problem.
Well, first, a warranty repair should be done ASAP after the flaw is
noticed. Don't wait for other problems to appear. Second, don't assume
what is causing a problem. Now the dealer can say the did what you
asked, and will be reluctant to do more.
Possibly bad rotors, as you suspect. They could easily be warped, or
have excessive runout. Can't say until diagnostics are performed.
And when you do tell them you want something, ALWALYS get a price. I
learned that the hard way....I asked them to replace the brake
retainers figuring they couldn't be more then a couple bucks each.
When I got the bill I was about to call for the manager to figure out
why it was $70 higher then I expected till I saw what they price was
for the brake retainers......
When you suggest a repair technique,
Not sure where you are, but consumer protection laws in most states
govern this, and when a customer asks for a specific fix or action,
they are required to do it. I've never seen a shop that would do
something else, they risk the customer's rath and a complaint to the
state if they do so.
That would be something like going into a bakery and asking for a loaf
of white bread, being given a loaf of whole wheat (because it is
healther) and that substitution being OK.
Clearly the OP didn't, or he would not have specified a repair that
was ineffective and probably unnecessary. I saw no indications of
technical skill, no indications of any diagnostic process other than
'assume', 'assumed' and probably a bit of guess and by gosh.
Again, no, this is not the way things happen. At least in most states.
You ask for something specific, that is *exactly* what they must do,
or do nothing unless you say so. So often it is inpossible to
determine whether the customer's request is reasonable or going to
resolve any problem, so the shop will do what the customer
requests--provide that loaf of white bread.
Oh, hell, you can disagree. I'm respected in my field, and know what
I'm saying (and when someone comes to me and asks for a specific
repair or process, I make it a point to impress on the customer that I
cannot ensure that the repair will do anything other than cost him/her
The OP would have been much better off just taking it in and saying:
"Here is what happens, please fix it", instead of suggesting repair
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