re: "Google Wallet may be making a return" (and "Why is it so complex

1. A test that didn't exist until 2013.

1. A test that no manufacturer is required to pass.

As I have stated, you can have a *warped disc* and *not experience* judder, shudder or the like. You see, a warped disc does *not* lead to a

Correct. If the actual disc warps, you will get the same kind of runout as you experience with the disc not sitting flat on the hub. I have had runout of that nature on discs that are *integral* with the hub. In most cases, but not all, that runout is caused by incorrect wheel nut tightening.

These days, given the disposable nature of discs, it is probably advisable to dispose of discs rather than trying to dress them up on the lathe. Back in the day, discs were a rather expensive item, these days not so much.

You look at *several* symptoms, not just the runout alone.

Inability to discern the difference - common issue.

Don't think we had the Toyota Tundra in this part of the world.

Using either a micrometer or dial indicator, I can measure variations to half a thou. I could go better but I would need to spend a lot more money on the equipment and it simply isn't necessary. Nor do they make brake specific measuring equipment to, say, 0.0001" accuracy.

See above.

Yes, this excerpt is *classic*.

My 2008 Mustang GT shakes at around 60-65 mph when braking. The Hurst five-speed stick shakes, too. When this is happening, the steering wheel moves from side to side.

I have had the *shimmy* (steering wheel moves from side) without any other symptom such as Judder or shudder. A lot of people used to confuse the issue with wheel balance or other steering defects and spend a fortune chasing the real fault. The clue was, and is, in the fact that the issue only occurs under braking, sometimes even very light braking.

Well, yes, uneven rapid cooling of the disc, that would do it.

That said, my only experience of warped rotors is with the non-ventilated variety.

Isn't it amazing how Arlen continues to argue with someone who quite obviously has lots of hands on experience with the subject...

...because he's "well-educated".

:-)

I recall my first vehicle with disc brakes. The rotors were thick, heavy, and massive. The pads were very small. The rotors never warped (or deformed, or whatever someone wants to call it) but the pads had so little surface area that they wore out quickly and could overheat on steep downhills if the driver didn't downshift to use engine braking.

It was not a great brake design but it was pretty simple to change the pads, and I had to do that often.

Yep, done that, seen the warp, many, many times!

I liked the way he did that final non-directional finish. I used to do it the hard way, that looked easy in comparison.

You're preaching to the converted. Well, not so much *converted* as

Oh, I understand that you understand.

But it's great that you've replied, as Arlen/Andy/....who knows how many others...

...has me killfiled for providing exactly this kind of clarity.

I'm up to 120,000 kilometres without any regenerative braking.

Looks a lot like *warp* to me. ;-)

I don't think I would be bothered even starting to machine that one - binned!

The comment that goes with it very nicely matches yours:

'"No such thing as warped brake rotors." I've heard that saying spread around quite a bit. "What you're experiencing is merely uneven brake pad transfer." While pad transfer is a phenomenon that exists and one that I've encountered, I spent 8 years as an automotive technician and witnessed warped rotors regularly, this case being one of the worst. Be assured I setup the brake lathe properly and no tricks were done to make this appear any sort of way. I even double and triple checked my setup to prove to myself that this rotor was indeed as warped as you are seeing.'

It is actually so the rotor can *hold more heat*. It's all about

- it's related to the above point. Also, the thinner the disc, the greater the likelihood of warping related to strength and heat holding capacity..

Yep, as oft stated, I've felt it, seen it, measured it, machined it.

People who think rotors warp also firmly believe the earth is flat. There is no discernible difference between those two belief systems.

They're both imaginary; they're both strongly held; & they're both wrong. All the professionals, in this case, Raybestos Training, say so.

Within a short period of time after that replacement, the vehicle came back again with the same complaint of pedal pulsation.

Today what we are going to do is dispel the myth of warped rotors and show you the diagnosis procedure to help eliminate pedal pulsation.

Many technicians will diagnose pedal pulsation as warped rotors. Let's dispel that myth right now. *Rotors do not warp.*

_There is no brake system that runs 2,300 degrees._

Let's take this apart and see what the issues are that causes the thickness variation.

Typically, every time a vehicle comes into a shop with a complaint of pedal pulsation, the technician looks at it as warped rotors. As I mentioned before *rotors don't warp* but what causes a pedal pulsation is disk thickness variation.

Disk thickness variation is caused by excessive lateral runout. Let's take a look at this rotor and see if we can identify some areas that have caused this condition.

When we look at the rotor, you can see some black marks in the rotor. Typically what that is, is friction transfer from ceramic brake pads.

Ceramic brake pads lay down a coating of friction material. That has been laid down unevenly which ends up being thickness variation, causing pedal pulsation.

When you turn the rotor around the other area you want to look at is the mounting area.

We can see a big rust buildup on the hub area.

As you can see on this hub there's a lot of rust buildup. This rust can cause excessive lateral runout which induces thickness variation.

Let's get this cleaned up. Then we can either replace the rotor or machine it."

Note I'm quoting _reliable_ sources, not bullshit youtube videos from some teenager in NJ who can't mount a rotor on a lathe straight.

The fact remains that rotors don't warp. Anyone who believes they do also likely believes the earth is flat.

Most people persist in owning completely imaginary belief systems. Like I've been saying, intuition is a terrible thing indeed.

Let's stop this nonsense since no amount of facts, logic, and reason will convince some people the earth isn't flat.

Most people believe their intuition only, & not in any facts.

Dude:

You've been told by a professional in the field and you've been presented video evidence.

You're a complete and utter ass.

You can get thickness variation in a rotor that has *no* pad material deposition. The most typical cause is the creation of *hard spots* in the rotor that typically wear *less* than the rest of the rotor. Those hard spots are created by the rotor being *overheated*.

The problem with hard spots that cause thickness variation is that you are often unable to *machine* the rotor. What happens when your lathe tool hits the hard spot is it deflects and rides over the hard spot. In these cases the rotor can only be *ground*. Of course few brake shops are equipped to grind rotors and the cost would be prohibitive given the general cost of a new rotor. The problem anyway with hard spots is that unless you go deep enough to remove the hardened area, the problem will recur. Also, by then the rotor will likely be *undersize*.

I beg to differ. Had you ever done any rotor machining with a decent brake lathe, you would know that it is very difficult to screw it up. That disc on one of the videos was quite clearly warped. On another, the machining process clearly showed the warpage as it cleaned up. I too have seen this exact same thing very often when I have been machining rotors.

I believe in what I see, what I feel, what I measure, etc. And I have seen warped rotors, I have cleaned up and put back into service lightly warped rotors and I have rejected rotors too far gone to clean up. And yes, I have seen all the other types of rotor faults too and, what's more, I can differentiate.

And Arlen will continue to insist that his "education" (which he won't substantiate) trumps your real-world experience and knowledge.

Maybe we’ll get to see some more of his book pictures.