I have a 2017 genesis G 90 that will occasionally suffer from brake fade and vibration. I drive a lot for work and often through mountain passes with steep inclines and declines. I do notice on my left front rotor there are two significant lines that may be caused from embedded buildup underneath the brick pad rotors. From previous research I’ve noticed that rotor warping may be a myth and getting the rotors turned versus buy new rotors and pads is a preferred alternative. What is this community’s opinion on rotor warping and turning rotors versus buying a new set? I will include a picture of the left front rotor in question.
I don’t know any parts stores that turn rotors anymore…
The reason is, the cost of replacing rotors has dropped where it just about approaches the cost of turning rotors. Rotors on the vehicle are so thin from the factory to save weight that turning isn’t worth it.
And most importantly, the proper finish has to machined onto the rotors in order for the brake pads to bed properly. New rotors have this proper finish
Tester
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I haven’t had rotors turned because of what @Tester said above. But for some unknown reason I had my Taurus rotors turned, probably because I was feeling rebellious. Few months later I have minor warpage. If you use brakes a lot, turning them seems to me wouldn’t be a good idea because of heat damage.
It seems to be pretty much consensus here that purchasing new replacement rotors is the better choice for modern vehicles. In any event it may be nearly impossible to find a shop who has the equipment to turn rotors anymore, for this same reason.
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Save the old brake rotors, after you collect a dozen or so of them take the rotors to the scrap metal yard, they will pay you by the pound for brake rotors.
The shop I work at has 4 brake lathes, replacing brake rotors every 10,000 to 25,000 miles can be costly.
Napa still turn rotors here. Some cars have rotors so cheap that it doesn’t pay to turn them. Some cars have $100 rotors.
Warpage is no myth, however brake pad material buildup on the rotors especially in areas where road salt is used can mimic it. Rusty rotor surfaces can grab pad material.
A bigger question is brake fade, this may mean you are getting the fluid so hot you are boiling it and could lose braking altogether.
On long steep grades you have to learn to use your transmission to slow the car downhill.
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It might be a caliper issue. Is it hotter than the other side?
When in the mountains, on the roads you describe, at the minimum, turn off the overdrive. Driving two lane roads in the Appalachians I locked out 5&6 on my 6 speed transmission, made driving much more controllable.
… and downshift to 3rd or 4th gear. Brake fade is almost unheard-of on modern cars, and if it is taking place that suggests that the OP is “over-using” the brakes. Holding the car back to some extent by downshifting will cause him to use the brakes to a lesser extent.
Also, if the brakes have genuinely been fading, that suggests that they have become extremely hot, and that means his brake fluid needs to be flushed.
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But then he can’t do 80mph , he only has 20 minutes to get that pizza delivered.
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I think it usually works out better to get new rotors.
As others have asked, are you downshifting properly on the downhill sections?
In your situation, you’ll want to make sure that you change your brake fluid according to the maintenance schedule.
Mountain driving can be hard on brakes. That’s why they often have a brake temperature checking station halfway down from Pike’s Peak. If your brakes are too hot they make you wait until they cool down so you don’t lose them.
As others have said, check to make sure you don’t have a stuck caliper. The next time the brakes fade, get out and carefully touch a lugnut on each wheel. If one wheel is significantly hotter than the wheel on the other side, you’ve found your stuck caliper. You can also do this with less risk of pain with an IR thermometer. You can get them at places like Harbor Freight for around 20 bucks.
Beyond that, check your driving style. A lot of people ride the brakes all the way down the hill. That’s fine for actual hills, but if you do that in the mountains you’ll boil your brake fluid. Use the transmission to keep yourself at sane speeds while descending. Back when I lived in the Rockies, it wasn’t unusual for us to run the 3,000 foot descent from the peak in 2nd gear.
+1
And, for those who say that this will damage the transmission, all I can say is that I have been downshifting on steep downgrades for all of the 54 years that I have been driving, and I have never needed to do transmission repairs on any of my cars.
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Rotors can warp, but I do think that is rare. Generally if you are feeling a pulsation in the brake pedal and maybe a vibration in the steering wheel, it is due to a build up of resins on the rotor from the brake pads. If the steering wheel is shaking back and forth (left to right) violently, then the rotors are actually warped.
Low quality, low priced brake pads have a higher resin content and tend to contaminate the rotors more quickly. Low cost rotors that have more porous casting can also absorb those resin residues more easily.
Brake pads a made by mixing the friction material with resins and pressing them, sometimes under a vacuum, into shape and baking them under pressure. Better pads will have less resin and more friction material but require much higher pressure to make sure the resin surrounds every particles of friction material and there is no air in the mix. This makes the pads last longer and work better and withstand higher temperatures.
When I get the pulsing, also called shuddering, my first step is to make a couple of hard stops, just short of lock up from 60 mph down to about 5 mph. After two of these, the shuddering will usually stop as the high heat generated will burn off the residues from the rotors. In your case I would be careful as that picture looks like the pad on that side might be getting thin and maybe time to replace.
W.r.t turning rotors, it may be worth it if the shop has a lathe capable of doing on-the-vehicle turning, that can help correct for issues with tolerances on other parts of the braking/suspension system building up and causing a warping-style feeling in the pedal.
If you’re actually remove the rotors to turn them on a bench lathe, don’t bother. Not only is the extra cost for new rotors not significant, but since it’s hardly done anymore, my thought is that there’s too much of a risk of some inexperienced parts guy doing it wrong (and then you’re getting new rotors anyway).
Pulsation/vibration is due to thickness variations of the metal.
Tester
Your article isn’t quite accurate. I spent a few years in the metal casing industry and according to metal casters theory, rotors can warp.
After casting, metal can and usually does have stresses due to uneven cooling in the mold. As the metal is reheated, and it does not have to be reheated to the casting temperature, the stresses can cause the metal to change shape (warp) slightly to relax the stresses.
One way to avoid this is to season the casting before machining, which is to heat it up to a preset temperature (varies with various alloys) and let it cool. I doubt that cheap rotors are seasoned before machining. Cast Iron generally doesn’t have as much stress as say cast aluminum, but it does have some.
That’s not my article.
That’s a Brake & Front End article.
Tester
Thanks for the help everyone, I appreciate the input and will most likely be doing a rotor and pad replacement. I do use my transmission to slow down on the declines but not as often as I should.
I’m getting hungry for pizza now … lol …