Our Mazda CX9 needs the front brake pads changed. I inspected them today and I have very little pass material left on the front brake. Changing the pads myself is not a problem, the only thing I’m unable to do is turn the rotors myself. Usually when I change pads I take the rotors off and bring them down to our local NAPA and they’ll turn them for me.
I inspected the rotors and they appear to be in great condition. The only issue I detected was perhaps a slight glazing, but they are smooth as a baby’s butt when I run my hands across them. So, is it acceptable to just replace the pads without turning the rotors? If so, then it’s a quick job, I’ll just need to remove the old pads, push back the pistons and drop new pads in. I shouldn’t even need to bleed the lines (someone correct me is I’m wrong on this part).
Thanks in advance. The local repair shop wants 200 clams to replace the front pads. Granted, they’ll turn the rotors for that price, but if I don’t need to turn the rotors I can do it for well under a $100.
Absolutely acceptable and actually even recommended to leave the rotors be if they don’t show problems (gouges, too thin, warped). There should be no need for bleeding.
It’s best to use syntheticbrakegrease for where the pad backing plate meets any metal part.
If you don’t machine your rotors, then your new pads will squeal. Even if your finger can’t detect the grooves and waves on the rotor, rest assured that they are indeed there. Especially if your old pads are well worn down. Additionally, new pads on old rotors will wear both the pads and rotors rapidly.
I always recommend replacing rotors, rather than machining them. Removing metal reduces their thermal mass, thus increasing susceptibility to brake fade. Also, it’s something you can do on your own, versus machining the old ones. You can probably get the parts for cheaper than a shop will charge you to turn the old ones.
YMMV, I guess. I’ve replaced pads without turning the rotors, without squealing, and without rapid wear.
Also, always replacing rotors seems a little extreme. As long as the rotors are within spec for thickness, they likely don’t have to be replaced. Also, cost to replace is very dependent on the vehicle. On my Japanese cars, rotor costs weren’t high, but on my German cars and motorcycles they $ure were expen$ive.
That was generally true 20+ years ago, and may still be true with cheap pads, but is not the case with modern high quality pads.
Not in my experience. They may wear a little faster (a few percent) than with new rotors, but not rapidly – unless you’re using cheap pads or the wrong pads.
I’ve been doing my own brakes for 30 years and I have never once turned the rotors while changing pads.I don’t use el-cheapo pads, and I have never ever had a problem with squealing or excessive wear.
I did replace one set of rotors but that was because the pads had worn down to metal on metal and had gouged the rotors.
Gary T would know better than I do, but I was under the impression that you really don’t want to turn the rotors on a lot of newer cars. In an effort to reduce weight and cost they make them about as thin as possible and they often won’t have enough material left after turning.
I as well have never turned rotors and was also recommended not to do so. Not because it wasn’t necessary but that turning the rotors would typically render them past their spec and would then require replacing them.
A mechanic told me that it was a common ploy for the “brake shops” to say that the rotors were warped or some such, then suggest that they be turned, and then they’d come back and say that now the rotor was out of spec. So, after you spent all that money to have them turn them, now, you had to buy new rotors anyways.
The car manufacturers were telling people to change the rotors when changing pads… but its also known they had lots of inferior rotors out there… put there by the manufacturers.
The clue may be that the rotors put on the car by the manufacturer were inferior, so change them with the first set of pads … so that the manufacturer doesn’t pay for the problem, the consumer does.
Just an aside: Because of inexpensive imported Chinese auto parts I have not had a rotor or drum turned in a decade. They are always cheaper to buy new than get turned!
Shops do not exist to rip people off. They reply on repeat business, so they want happy customers. They also do not do things that are illegal, and fraud is generally illegal. I worked in a shop that did brakes, and sometimes we would tell people the rotors needed replaced, because they couldn’t be turned, and people would ask us to try turning them anyway, so we’d say that if they were out of spec, we would not put them back on the car, because it wouldn’t be safe; they’d have to buy new rotors, and still pay for turning the old ones. Most people would just ask for new ones at that point, but some people would want to old ones turned anyway. When they got told the old ones were not out of spec, and they needed new ones, they would sometimes ACCUSE us of ripping them off, even though they’d agreed to all of it ahead of time.
For the OP: do what you feel comfortable with, but know that the safest thing is to turn the rotors, check the spec, and put them back on only if they are still in spec (if they are out of spec already, don’t bother to turn them). If they are so warped it is visible, don’t bother to turn them.
Most shops don’t, but there are some that routinely oversell.
I think this is a bit misleading as worded. It’s not any safer to turn rotors if they don’t need to be turned due to gouges or warpage. It may even be less safe in that turned rotors are necessarily thinner than they were before, and the reduced metal mass can’t dissipate heat as well. It is certainly true that if they are thinner than spec, or will be thinner than spec after turning to correct a problem, they should be replaced rather than reused.
Bottom line, if the old rotors are thick enough (measure with a micrometer, as mentioned), flat enough (no brake pedal pulsation), and smooth enough (no gouges deeper than 0.060"), it’s generally better to use them as is than to turn them.
The only thing I have to add that hasn’t already be said: I went to replace the fronts on an old Nissan truck (damn fine unit!) and called to get a estimate on turning rotors. $80! :eek:
30 years ago, we replaced our pads, and never turned the rotors unless we wore right through the pads and ran metal-on-metal.
Then they stopped fitting asbestos pads. I have sintered metal pads now. Sintered metal pads are better – they grip better when hot or wet – but they are harder than the old asbestos pads, and they wear the rotors faster.
Worn rotors wear your pads faster, but not like they used to, using asbestos pads on worn rotors, because pads aren’t as soft and weak as they used to be.
I didn’t replace or turn the rotors last time, because I wouldn’t trust my dealer as far as I could throw the dealership. I have got squealing now, which I assume means I am also having greater/faster wear, so maybe I was wrong. (Wrong about having the rotors done. Not wrong about not trusting the dealership).
There are certain models of cars where using the el-cheapo semi-metallic pads will result in squealing. You would think that if you take the car to a dealer or a reputable big name shop that they wouldn’t put the crappy el-cheapo pads on, but sometimes they do.
We had this problem with an old Nissan Stanza that we used to own. Mrs. Geek wouldn’t let me do mechanical work on her car when we first met. Then she had this squealing problem after getting the brakes done. She paid a lot of money to have rotors turned and coatings put on. Finally I went out and bought a set of better brake pads and put them on, and the problem went away. After that, I was allowed to work on her car.
Your problem could be the rotors or it could also be the pads.
I don’t trust dealerships either. I’ve had too many problems with them over the years.
I grew up working on cars, but didn’t make it my trade (got into IT instead). Still, I’ve known and know car repair people and when doing a brake job it was/is considered SOP to *always *cut the rotors/drums regardless of their condition. Cutting them didn’t make it the ‘deluxe’ brake job, not cutting them made it the amateurish, shittier one. The fact that the rotors/drums are perfectly smooth is the reason you get them cut. They’ve been polished so smooth that the pads/shoes don’t ‘grab’ as well. If they were in good condition you might just do a fine cut (usually you did a rough & a fine cut) but the point is to make the surface microscopically less smooth so the pads grip better.
We would often do them without cutting the drums/rotors, we called it a ‘pad slap’, but only to our own cars if we were broke or a friend’s who was a cheapskate.
And good luck trying to find drums/rotors (or most any car parts) that aren’t made in China. You’d have to go to the parts dept at a new car dealership and you’ll literally pay five times the price (and they still might be Chinese). And Chinese car parts are generally not badly made. They’re inexpensive because their labor costs are about one 1/100 of ours.
If I may continue this hijack, can anyone recommend a brand or manufacturer of brake rotors? The Whatever Autozone Sold Me front rotors I installed about 20,000 miles ago on a Mazda3 are already showing signs of heavy wear, with substantial grooves and pulsing that’s starting to get serious.
