Front Rotors


#1

Has anyone had frequent problems with warpped rotors and was able to solve the problem? My rotors warp every few months…


#2

Vehicle, Year, Make.

Some vehicles are more prone then others.

Could also be the replacement rotors you’re using. When I replaced the rotors on my Pathfinder years ago the parts store had 3 different rotors for me. Two were identical…but the third was noticeably thinner. A thinner rotor will warp easier.


#3

2007 Lexus ES 350 - even the original rotors did not last long. A mechanic just suggested that I use ceramic pads instead of semi-metallic. The rotors I bought did not look any thinner - actually, a set I bought looked thicker and they lasted one month…


#4

One cause can be improper lug nut tightening. Pad type shouldn’t make a difference. I’d skip the slotted rotors, there’s little/no benefit to those. You might have a frozen/stuck caliper. A good brake shop should be able to help.


#5

Wife has the same vehicle. 45k miles…and rotors are fine.


#6

How many miles on the car? A loose wheel bearing or suspension component can mimic a brake rotor problem.

Another question might be if the shop is actually checking the rotors to make certain the’re warped in the first place.

If there is no worn suspension component and the rotors are legitimately warped then it could be your driving habits causing the problem.


#7

It’s a 2007 Lexus ES 350 I bought new. It now has 65K miles. I am not an aggresive driver, but this has happened to a TL I had, so maybe it’s me. The rotors are warpped - the car shimmers like crazy. I tried an after set which lasted one month. It seems like every 5 to 6 months, I have to do something to them…


#8

Shimmie or brake pedal pulsation? At this point I would want the runout on the rotors measured for confirmation and to get a clue as to what is happening here.


#9

“Warped” rotors is a misnomer. Oldschool mentioned runout and that is certainly important. Runout is what most people think of when they say “warped” rotors.

If you imagine and old style turntable/record player… run out is the distortion that causes the needle/arm to move up and down relative to the turn table platter. Runout all by itself has nothing to do with vehicle roughness as the brake caliper simply follows the rotor just like the needle follows the vinyl.

What runout CAN do is begin to induce THICKNESS VARIATION. That is, if there were two needles playing both sides of the album at the same time (directly opposite each other)… are they always the same distance from each other? In other words, is the disk the same thickness all the way around the rotor. It’s pretty easy to imagine how vehicle roughness or pedal pulse can happen when the disk is NOT uniform thickness. What’s not easily understood is HOW sensitive some vehicles are. Some vehicles produce roughness with less than 20 MICRONS of thickness variation.

T.V. (thickness variation) can be caused by runout. What happens is as the vehicle is driven (brakes NOT applied) the runout causes a slight rubbing of the disk to the pad… but only one at a time, and at opposite clock position of rotation. This causes one of two things: localized disk wear or lining transfer. Disk wear is easy to imagine, and it causes the disk to be thin at a particular section… therefore causing thickness variation. Lining transfer is exactly the opposite. Friction material is actually added to the iron of the rotor causing a localized THICK section. The effect is the same, thickness changes as the rotor passes through the brake and pulsing the vehicle or the pedal. The more runout (or the earlier the onset of runout) the more apt roughness will develop. Sometimes, a friction material is selected as OEM specifically to machine the rotor back to being true. This causes less roughness but results in rotors that have to be replaced almost as often as pads.

So… what to do. You can have the rotors turned to eliminate the T.V. but they’ll be thin and more susceptible to heat issues. Best thing to do is when replacing pads to do so only with OEM pads… which means going to the dealer.

Incredible amounts of R/D is put into choosing pad material and NVH is the primary driving force behind friction selection. Output is relatively easy to control with brake size. NVH is the killer that resources are being spent on.

Bottom line is friction material selection has a HUGE effect on vehicle roughness.


#10

I assume by shimmies you mean the steering wheel vibrates quite a bit. This points to the front end, but it’s not etched in stone that the rotors are the cause of the shimmy simply because it does this when you’re braking.

Checking rotors for warpage and parallelism is easily done so it should not be a guessing game to determine if they are at fault or if the problem is related to a loose wheel bearing or suspension component.

If one assumes a loose wheel bearing or suspension part is behind this problem it can be explained this way.
When the rotors are replaced or machined you have a straight surface on them. After a short time the rotors may get a couple of thousandths of an inch out of true. Nomrally you may not notice this small amount but if a loose bearing or suspension parts exists this small amount can become magnified and a shudder will develop that not normally be even noticed.

Considering the brake history of this car one would think someone would have thrown a micrometer and dial indicator on these rotors and verified yea or nay as to whether the problem is really the rotors or not.

Warpage is simply mechanic lingo for runout.
“Runout” may require an explantion but “warpage” is pretty much self-explanatory.


#11

“Runout” is actually an engineering term, a measurerment of total surface deviation from a desired parameter over a complete rotation. ASME Y14.5.

Warpage is one cause of runout.

I know, I’m being picky about semantics, I’m guilty as charged. But I’m just havin’ a bit of fun with you. You know I respect your knowledge.


#12

Since you had this problem with your pervious car also, an Acura TL, I have to ask…do you perchance drive with your left foot on the brake pedal?


#13

…or, do you rotate your own tires? If so, do you use a torque wrench to tighten the lug nuts?

Does your mechanic use a torque wrench when tightening lug nuts? If not, that is a probable cause of warped rotors on both of these vehicles.


#14

When you start getting the shimmies or pulsations, try doing a hard brake from 60 or so. Don’t lock them up but brake hard just short of that, and don’t come to a complete stop, when you get down to 5 or 10 mph, keep rolling and accelerated back to speed and repeat one or two more times. You may find it all clears up for awhile. Repeat when the problem returns.