Do I need to Turn Rotors when changing Brake Pads - What does Resurface Rotors Mean?

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Should you replace or resurface your rotors when doing a brake job?

Like brake pads, brake rotors don’t last forever. The rotors wear every time the brakes are applied. The rate at which rotors wear depends on a lot of variables: the type of brake pads on the vehicle, the metallurgy (hardness and quality) of the castings, how efficiently the rotors cool themselves, the type of driving the vehicle is subjected to, the braking style of the driver (aggressive or easy) and exposure to moisture and road salt.

Semi-metallic brake pads usually contain a very high percentage of chopped steel fiber, so they typically cause more wear on the rotors than most ceramic or nonasbestos organic (NAO) brake pads. On vehicles where rotor wear is a problem, switching to a “softer” friction material (such as ceramic or NAO) may solve the problem — provided there’s a choice of friction materials available for the application.

The quality of original equipment rotors can vary from excellent to questionable. Most carmakers insist rotor quality is extremely important. After all, the rotors are part of the brake system and safety is paramount. Yet some original equipment rotors come from the factory with hard spots, inclusions, impurities and other junk in the cast iron that undermines their durability, wear resistance and performance. Good metallurgy is critical because it affects the friction qualities of the rotor as well as its strength, hardness, sound characteristics and even its corrosion resistance.

As a rule, most original equipment rotors used to be designed with enough thickness to go two or more pad replacements. But on some cars today, the rotors are thinner to save weight and cost. Consequently, the rotors may be worn down to minimum thickness specifications (which is usually marked on the casting itself) by the time the first set of brake pads need to be replaced — or even sooner in some cases.

The minimum thickness specification is an important dimension because it is the minimum thickness that provides safe braking. As a rotor wears and becomes thinner, it has less mass. This reduces the rotor’s ability to absorb and dissipate heat. It also reduces the strength of the rotor, increasing the risk of cracking or even breaking (rotor failure).

That’s why the thickness of the rotors should always be measured every time the brakes are serviced. If a rotor is worn down to the minimum thickness specification, or cannot be resurfaced without exceeding the dimension, it must be replaced. In some states, this is the law.

Great article on rotor science:

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Good info. Especially about advantages of a seasoned rotor.One would assume a new rotor would be best. Apparently not. Thank you.

tsabo
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Dont forget to look for the minimum thickness of your rotors before getting them resurfaced, you should find a decimal number in milimeters (mm) somewhere on the rotors, when resurfacing you will lose some thickness and they may not be useful after that. Use a caliper meter to measure out the thickness.

Ben-nxyy
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Def what I was looking for! The seasoned part makes perfect sense… thanks mate!!

adelk
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there may be a cutoff point though. When "resurfacing" you are losing mass on the rotors...the same energy will be applied to the rotors as before...with less material from the rotor resurfaced there is more heat created than before for the rotor to endure....

jayman
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I would just replace the rotors every other brake job. Here in Chicago, by that time the rotors have some pretty significant rust from the salt.

stevenschoenfeld
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In my experience, if there is no pulsation when braking but there is a little scoring, it isn't necessarily time to have them turned. The new pads will quickly wear to the surface of the rotor as the rotor mates with the pad. There will actually be more friction surface, which isn't a bad thing. Of course, you have to use your head and ask yourself after checking with a micrometer or dial caliper if the rotor thickness is still above the minimum and/or the surface grooves are not excessively deep. A clue that the rotor is due to be replaced is if the outer wear margin on either side is leaving a pronounced ridge. New rotors are very reasonably priced and a snap to install, so when in doubt, just replace them. I have been through this many times. The incident that encouraged me to do my own brake jobs (about six as of now) was that I was cheated by a locally respected tire store that told me the rotors needed turning and I gave them the go ahead. If they have mic'd them before turning they would have known immediately that there wasn't enough meat on the rotor for turning. They came to me with the news that they tried but, alas, new rotors will be needed after all, so I got to pay for the turning AND two new rotors. Been doing my own ever since. Good thing it's fun to do, eh?

williamthomson
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Great job explaining. Got right into it brief thorough and simply understandable!
Thanks!

meklitsolomon
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I agree i have new front Pads & Rotors with only 9K miles on them (slide pins lubed) and they vibrate when braking at high speeds! The key word here is now they are "Seasoned" so i agree I'll have them turned and install a new set of pads to resolve the vibration issue vs. getting new unseasoned Rotors which may end up vibrating again.
Thanks for bring this to my attention... my faily new Rotors have bern giving me hell.

djuanejackson
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Consider three things before resurfacing.

Original thickness ( most front rotors have more pad contact surface to be able to turn. Some cheap rotors especially rears which may be originally cast just slightly above the minimum thickness.

Rotor material: how well the materials used during casting were mixed, heat treated and allowed to cool properly.

Rust preventative coating applied: Most modern rotors have some sort of rust preventative applied at the factory before being shipped. Black is a common due to the fact that as the rotor contacts the pad the rest of the rotor should still have the protective coating applied but the pad/rotor contact surface will turn metal. Some have the same coating applied but maybe clear and although not seen the coating is there.

Zinc is a common ingredient used in this step.

Not sure if it is still done but they used to spray a small coating of oil on the rotor and seal in a bag to prevent rust during transit. The coating is obvious but the bag prevents the protective coating from being absorbed by the rotor box weakening the box structure.

In general I would not expect to be able to turn modern rotors more than once and another resurfacing 20-30K miles later might be at or below minimum thickness after resurfacing.

Yes there are crooked shops out there but this is one that is a major safety item and they will not budge.

stephencannon
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Who disliked this video? The people that sell brake rotors maybe! Great info. Thanks!

SoulFire
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Turning rotors is one of the biggest fleecing jobs in modern automotive maintenance. Sure there are times when it's needed. Some mechanics are raping people with the idea that every brake job requires turned rotors. Rediculous. I've run metal to metal a few times on different cars and never turned the rotors. Guess what happened? Not a damn thing. No amount of hard braking or downhill braking changed the performance of new pads on old rotors. Now I did have an issue with one car when I first replaced the pads. The worn rotor grabbed a bit more. After a while though, smooth sailing. Show me proof, real world proof, that non turned rotors make a difference for the average driver. It doesn't exist. The automotive maintenance industry is one of the most under handed and rife with falsehoods. If brakes are broken, they will let you know. Don't drink the koolaid.

shawncox
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Hate to be the voice of dissent; but depending on your driving habits, it's sometimes perfectly fine to NOT resurface a rotor when doing a brake job.  How do I know this?  I did the first brake job on my Ram at 68, 000 miles, and bought new Wagner (a good name) rotors.  I immediately had brake shudder for the first time ever.  Every time I applied the brakes at more than 45 mph, the car shook.  I took the job apart, applied new high-heat synthetic grease to the slide pins, and made certain that the hub onto which the rotor was attached, was wire-wheel cleaned and like new.  Still same issue.  I put my old, NOT resurfaced rotors back on, and problem solved.  When I took the rotors back to the automotive shop and explained what I did, they exchanged the rotors for a new pair.  I now have a new pair on "the shelf" and will maybe use them in 80, 000 miles when I do my second brake job.  Appears the new rotors were garbage.  And to think. . . I did my research and bought a name that was second or third on the list of "reputable manufacturers."  Come to think of it, next brake job, I might just have my Mopar original rotors resurfaced for the first time.  Anyone want to buy a new set of Wagner front rotors for a 2015 Ram 4WD diesel?

freddiemercurious
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Great advice. My Dad was a master mechanic... He told me years ago... when you do your brakes be sure and turn your rotors, 2 flat surfaces will stop much faster and brake pads will last longer. I have a spare pair of rotors for the front and rear.

redwhiteblue
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Unless your rotors are warped or seriously scored or very worn, which is very unlikely, there is never & need to replace or turn rotors! It's just a big $$$ con!! One can tell if they are warped because when you break, you will get a thumping/jerking stop. This is also a very rare thing now that most rotors are vented. Old solid type rotors could get very hot & warp if your calipers got stuck. Not very likely today because of improvements in design!

rrtv
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The problem with turning rotors is that you thin the metal every time you turn them. They become weaker with every turning, making them more apt to warpage. On my own vehicles I don't turn rotors, merely replace the pads (pads are cheap) and clean/grease the sliding pins. NEVER had brake rotor problems, ever.

dynamarkets
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Metal has built in stress that can be relived with heat. I agree with what you said, once the stress has been relived it should take higher heat to stress it again.

One-eucn
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I’ve changed pads without doing anything to the old rotors. They usually squeak for the first few hundred miles until they wear in, but usually it ends up working just fine. Squeaking is of course unacceptable in a business unless the customer is informed.

stephenmartinez
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how much is the cost for the rotor resurfacing ... do you know

droope
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You have three options. You can just put the pads on. The pads and rotors will adapt to each other real quick with proper break in.

aluisious
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Replacing rotor labor is about 50 per wheel. A pair is 100. New Rotors costs about 100 to 120. Brake pads about 120 part and labor. Total about 340. If resurface rotors, how much does it save?

Fried_chicken_burger