[hyperv6]

First off Warped rotors are a myth.

Two things happen that causes this.

#1 The most common cause are brake pads not bedded in. When new brake pads even on new vehicles need to be bedded in in a series of tops to Coat the rotors with pad material evenly. This prevents pads from leaving pad material unevenly on the rotors that creates the pulse of the rotors as the surface has embedded material on it in uneven spots.

Often using the brakes hard off a off ramp will get them hot and as you sit at the light the pads deposit material on the rotor if it has no coating.

Go to any major pad company and in their tech section it explains how and why to bed your brakes.

Replace or light cut the fotos to Coleman them. Racers use a set of aggressive pads to clean the rotors in practice.

#2 the second cause is a hub bearing that has a little too much play. This will let the rotor wobble a little and bounce off the pads wearing it uneven. While many think it is warped it really is just worn uneven in thickness. It is called RTV Or rotor thickness variation. Note that this was not an issue in the past when roller taper bearings were used. Today they used roller bearings that are more efficient for more mpg but can wear or can be damaged more easily.

Highway miles will cause more uneven wear than city driving.

People on the web claim warp but cast iron can warp in very extreme cases it is rare to very rare. Just look at exhaust manifolds and racing brakes that get red hot and never warp.

You can find this issue on most brake company tech sites.

Also google warped rotors br Caroll Smith and he wrote a very good story and NASA one of. The best chassis guys in racing.

-Warped- Brake Disc and Other Myths

I hope this helps as so many Blame warp cut or replace rotors and only to have it return. Cutting is treating the symptom but not fix the cause.

Some will want to disagree with me but this is not my opinion here this is what I have been taught by major brake mfg I deal with at work.

Also vented rotors do noting but look good. They do not cool. And if not made right can fracture. Look at all major racing series used solid rotors with groves for cleaning the surface of the pads. The solids are the best heat sink to draw out heat from the pads to prevent fade. The key to good brakes is to transfer and disapate heat. Holes in the rotors removes heat sinks abilities.

The real reason to make holes was to out gas pads but today that is no longer needed. Also it was for less unsprung weight on race cars for handling.

Drilled rotors like Willwood states is for cosmetic reasons only.

I hope this will help. I used to think warp too till I went trough training and now I have no issues.

 

[hyperv6]

Yup ...sounds like warped rotors. Curious of what 'adjustment' they made. Squeezing usually means the pads are just a bit too close to the rotor - proportioning might be off ( per say).

Also....check the torque on your wheels. If the wheels are torqued too much, it can warp the rotors.

Yes if there is a warp issue it is often torque related but mostly to small or light rotors. Honda rotors are known for this and are sensitive enough the recoded cutting them on the vehicle just as a growing number of other mfg.

 

[hyperv6]

This is exactly correct. Warped brake rotors used to be pretty common - about 50 years ago. C'mon , guys, it's time to move in to the 21st century. If you haven't taken the time to read the linked article, you should. It's short, but loaded with good info. And Carrol's been dead for a long time now, so it's not really new info.

If the rotors were warped, it wouldn't matter whether they were hot or cold. They'd just be warped all the time.

As said above, it's most likely brake material deposited unevenly on the rotor. You don't notice it much when they're cold, because pad material works better when warm/hot. A lot of time you can look at the rotor and sort of see an outline of the pad.

Most modern brake rotors can't be cut. They're already pretty thin to begin with, and there's no extra meat there to work with. But, you can resurface them. Use 80 grit sand disc in a drill motor. Give them a nice even surface, and make them shiny. It only takes a few minutes. Do both sides of each rotor.

It wouldn't hurt to put a new surface on the pads, either. Since the pads are out, clean the backside and use some Disc Brake Anti-Squeal goo.

Then bed the pads in as if they were new.

Or, just drop it off at the dealer and let them fix it.

Yes for sure things are not like they used to be.

Back in the day things were much different than today. Today systems may look the same but materials and sensitivity are much different today.

I need Togo bed my new Denali pads today. I just picked it up yesterday. Most mechanics are also behind times as few bed pads.

 

[hyperv6]

Warped rotors aren't a myth....they exist.

Perhaps the word 'Warped' is the wrong term. Mind you....if a rotor is even slightly out of round - its considered WARPED and needs to be turned or replaced. Rotors get OUT OF ROUND for a variety of reasons. From cheap-azz &/or thin monkey metal rotors that can't withstand the heat to bad wheel bearings, poorly functioning calipers, bad proportioning, bent wheels, and the list goes on.....
Depending on the 'thickness' of the rotors and how 'out of round' they are - will depend on whether they can or can't be turned.

I've had my own fair share of 'out of round' rotors - from wheel bearings, bent wheels, to Manufacuturers cheap parts & poor setup.

The one thing is true - no matter what you believe..... If you have a vibration when you drive and especially while putting on the brakes - you can't ignore it.

Don't tell me tell the brake mfg's.

Rotor thickness variation is uneven wear not warp.

To be honest most well trained people do not even turn rotors much and if they do they do it in car.

Just because a rotor has run out does not make it warped. It is due to wear.

You can get a rotor red hot on a race track and it will not warp. Even a stock rotor like many weekend racers us.

More often they crack as cast iron only gives so much.

Some thing else to consider too is calipers are floating and when applied even with a rotor out of spec it will move with the rotor unless the thickness is compromised by wear.

 

[hyperv6]

While there are many things that can cause a shudder like warped rotors. (that isn't a warped rotor) I have to say I have turned (machined) hundreds (if not thousands) in my career that were absolutely, positively, warped. Saying warped rotors are a myth is just ludacris.

Did you check it for thick ness variation?

Putting an uneven rotor on a lathe it will cut and sound like it has a warp but the rotor is worn uneven due too much play in the hub.

Like I said if disagree with the warp myth then tell EBC, Willwood, Bendix, Powerstop, Hawk, Rabestos and many others you disagree. I am measly the messenger.:grin2:

I do see often people cut rotors and repeat the same issue because they never bedded pads or check hub play.

Cast iron can warp but it is very rare and seldom seen on rotors more often it will show cracks if deflection that far out.

If it does happen it is due to torque on a very small rotor.

 

[hyperv6]

I get what the problem can be with hub looseness or uneven torque and such. But I mean when you put the rotor on the lathe it looks like a potato chip. I really don't think they wear that way. Too bad I'm retired now so I can't look at it now. I do like the idea it is only wear from loose bearings or dirt on the mating surface or whatever. But after seeing hundreds of rotors like that I just don't buy it. Also, how could it be wear when it happens after one panic stop? Seen that too. I suppose it could be pad material on the surface of the rotor? Anyway, interesting stuff either way. I suppose it could be an optical illusion, but I just don't think so. Maybe it depends on the type of rotor too? Don't know.

Nothing personal taken here we are good. This is not my opinion but what the MFG teach and state.

Now there are issues also that are specific to some systems.

Like the system GM uses on the Older Malibu, HHR and other GM Fwd cars. The bracket that holds the pads has stainless clips but the cast iron bracket rust and enlarges then binds the caliper wearing out one pad and the in side of the rotor just rust and looks like a mess.

Now I see many good mechanics miss this stuff as they think the brakes look the same but the have changed much.

Bearings. Material of the pads howthey mount etc.

It sounds like you have been around for a while. You may note much of this was not an issue till Fwd came around with the ball bearing hubs. Also since then even Rwd uses the same type bearings now.

It takes so little to be out to cause issues. Even needing a curb can set it off.

Either way that is what is taught and stated.

 

[hyperv6]

So I pulled the tires and cleaned the rotors. Guess there was a little material build up somewhere because they do not shudder now when I brake. Thanks again for all the info as always!!

Good to hear. Beware it could come back with warm weather. It may be gone now but there may still be a spot that could collect the material again. If you got it all you will be fine if not it may reappear.

Variations of rotor contrition and pad material along with driving habits and locations can all be a variable.


You can go out and bed the pads now. The pads do not need to be new. It will cost the rotors and help prevent it from returning.