Some years ago I believe brake pads were replaced, rotors were milled down if possible and replaced if they were too thin.
Now I am being told it is cheaper to replace the pads and the rotor at the same time.
The rotors start out around 10 mm, I hear recommendations to replace the pads when they have 2-3 mm left on them.
My question is - if I replace the pads with material left and the only downside of leaving them on until they are totally gone is scratching the rotor which I’m going to replace anyhow, why not leave them on until there is no material left?
The upside, obviously is I get more miles on the discs before replacement.
Thanks to anyone who answers this
John Neglia
I meant the pads start out at 10 mm, not the rotors
John Neglia
One downside is: if you delay until the mounts are scraping the rotors, then you have very little braking ability left and that’s bad in an emergency.
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It appears that you are replacing the pads and rotors yourself. That’s what I do. I find that waiting past the wear indicators scratching the rotors means that I have to check the pads more often to make sure when there is just barely pad material left. If you do that on all four wheels, it takes a long time. You can spend that time doing something else if you just replace the pads and rotors when the wear indicators tell you to.
If you have a shop do the work, I would replace pads and rotors together. The labor amounts to quite a bit and I had both done on my Toyota at 61,000 miles. I’m now good for another 60,000 miles!
Maintenance can be carried to the extremes and “If it ain’t broke don’t fix it” is argued by some to be a great way to save money but not for me. I rotate tires about every 10k miles and closely inspect the brakes then. If I can’t be certain that they will last till the next service I replace them. But I don’t replace rotors if they show no noticeable wear. And bleeding/flushing the brakes is part of the routine.
I’m glad to throw away 2 to 3mm of brake pad to avoid a brake problem that would likely occur at a bad time.
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My wifes Lexus has over 200k miles and I’ve replaced the brake pads on the front twice and the rears once…and NEVER have I replaced the rotors. Contrary to what many brake shops will have you believe, rotors don’t need to be replaced every time you replace the pads. I’ve had vehicles go past 300k miles on the original rotors (several sets of pads), and they were fine.
Rotors are cheap, but on some vehicles the rotors and hub assembly are one piece which makes replacing the rotor very labor intensive since the hub is pressed in. Not too many are built that way anymore, but they still do exist.
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There’s no one right answer to this. Some cars can go through 3 sets of brake pads before rotors need service or replacement. Some cars the rotors will be scored beyond reuse by the time the first set of pads wear out. Some manufacturers specifically state that pads and rotors be replaced together as sets. Some rotors cost $150 or more so resurfacing for $40 each makes sense. It all depends on the vehicle and the driving conditions.
As far a replacing brake pads at 2mm of lining, that shouldn’t need much explaining. Brakes that are grinding have failed. It’s generally understood that replacing parts before they fail is wise. I mean you don’t wait to replace a battery until it’s failed.
Exactly. And a failed battery means the engine won’t start. Failed brakes, on the other hand…
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Actually I think a lot of people do.
Since you have to jack the car, put it on stands, remove the wheels and inspect the pads… a LOT of work to just walk away from 2 mm of pad life AND you get to listen to the squealy tab for the last 2-3 mm of wear? Just change 'em, life’s too short, IMHO.
As for the rotors; Yes, Chinese rotors are cheap (and crap). Better rotors cost more but resist warping and last longer so re-using them may be an option. Turning them can cost nearly as much as new cheap rotors.
BUT, if the rotors are relatively smooth AND thicker than the minimum thickness (molded right ON the rotor) and as long as you don’t mind a little grinding or squealing noises until they bed-in and smooth out, you are good. Shops replace them with every pad change to minimize customer returns for noises.
The money saved running them until they are metal to metal is not worth the risk… my 2 cents.
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I have a jump pack in the back of my SUV waiting for the day my 5 year old battery won’t start it. But I have lots of room to carry the jump pack and my wife doesn’t drive the SUV.
Thank you Bill,
I had not considered that
john
I don’t replace my rotors unless they’re warped and thin, I just replace the pads, and since I have to take the pads off to assess the wear, and because they’re cheap, it’s just as easy to replace them as it is to check them. (I can’t see the inner pads until I’ve removed the caliper.)
How far your rotors go depends upon what kind of rotors they are, what kinds of pads you use, and how hot you get the rotors. My wife bought a 330i with 50k miles on it and the rotors were already badly worn (past spec) with OEM BMW pads. I bought a 325i wagon that the original owner had fitted with slotted ATE rotors. Those rotors now have 180k miles and when I recently replaced the pads, the rotors still looked like new. The front left rotor has warped, unfortunately, but they are not worn at all.
It also depends on the quality of the work when you get a brake job. The last time I let a shop do my front brakes, the rotors were warped right away. Evidently, they machined them poorly. I went back and had them re-machine them. I’ve been doing my own brake jobs since then, and I’m on my third set of pads using the same rotors.
On a slightly unrelated note, I still have the original drums on the back of my Civic, after 19 years and 300,000 miles. They’re so old the screw holes that are put there to help remove the rotors have flaked away to where there is virtually nothing left. They’re just rusty and stripped out. I don’t know how they got the drums off the last time they replaced the shoes. I usually do my own brake work on the back too, but since the pistons were leaking, I let a shop do the work when they replaced the pistons.
That’s true, if both are worn enough to be replaced. There’s not much extra labor time required to replace the rotor if done as part of a brake pad job. There’s not much downside to wearing the pads beyond the 2-3 mm point as long as they get replaced before metal on metal is reached. Once you reach the point of metal on metal you’ll experience greatly increased stopping distances. Pad material that’s worn so much to become super-thin might heat up and melt away during aggressive braking is another concern. Brake pads on my car last such a long time and great distances that I don’t bother to try to finesse the replacement timing to quite such a degree myself. When the pads look to be 75-80% gone I replace them. I only replace the rotor if it is close to the minimum spec dimension, as the rotor doesn’t seem to wear very fast on my cars. On newer vehicles as I’ve been told here the rotors tend to be pretty near the limit from the factory, so they often need to be replaced with nearly every pad change.
Thanks. Mike
It seems that there’s a wide variance on quality of rotors and pads your response was very helpful to me thank you
John Neglia
Agreed. I think almost everyone does.
Some advise (seems to make sense, but I have no way of knowing how much) that the friction material provides a thermal barrier that helps slow excessive brake heat from getting into the calipers where it can age seals and fluid and cause fading if fluid boils. Thinner pads provide less thermal protection so if I’m planning mountain driving I’ll replace the fronts at about half way, otherwise let them go to ~ 1/8in. and consider it cheap insurance. I haven’t had any problems taking rotors to their minimum spec., but have always used either the mfgr’s parts or a quality brand, same for pads. Have never turned a rotor, just deglaze them with emory paper (used wet) and only if it seems needed, with no problems or noise. Check, clean and lube the caliper sliders, have had uneven pad wear due to sticky sliders.