Turn rotors?

hyundai
veracruz

#1

Dealer says rear pads on my 2008 Hyundai Veracruz Limited AWD are down to 8mm and should be replaced soon. My regular mechanic says turning rotors is needed as well. Question-is it necessary to turn rotors if we are not yet down to metal?


#2

Rotors are all metal, so I’m not sure what you’re asking.

If you replace rotors, and then turn them, what you are doing is shaving perfectly good metal off of a brand new part and therefore significantly shortening its life.

If you turn rotors without replacing them, what you are doing is making the rotor thinner and therefore more prone to warp, which is why you turned them in the first place.

In short: I just replace rotors. They’re cheap, and it lets me go longer before I have to fool with the brakes again.


#3

Rotors are made entirely of metal. The PADS are not. On any brake job the rotors should be “turned” or machined smooth in order for the new pads to seat well and wear evenly. Today’s rotors are thinner and lighter and usually are replaced after the second turning.

A good brake shop will do these things since they don’t want you coming back saying that the brakes squeal or stop with grinding noises and vibration.


#4

Most rotors are so thin these days it’s not worth turning them. They will be too thin afterward and prone to warping.

If the rotors need work, replace them. If they’re not badly scored you could probably just put new pads on and leave them alone.


#5

I agree but then again I use a lot of aftermarket parts and do the work myself.


#6

Check your owners manual. If your brakes have wear indicators, they’ll make noise when you need new pads. At that point I’d replace the pads and the rotors, just get good quality ones.


#7

Thanks, all. the manual says that we have wear sensors, so we will keep an ear out for that screeching noise…


#8

The philosophy behind turning rotors is to remove any uneven surface to provide the longest life for your new pads. If they feel the rotors can be turned do it, it will provide the best braking.


#9
[b] Today's rotors are thinner and lighter and usually are replaced after the second turning. [/b] 

  More often today it is recommended to replace the rotors every time you replace the pads.  The difference in price is just too little to try and squeeze a little more life out of them, only to end up paying to replace them soon anyway.

#10

DOWN to 8mm??? 8mm is right around half life for a typical set of brake pads. You probably don’t have anything to worry about for another 20k miles or so, unless you are very hard on your brakes. If you like to wear your pads down to the metal, at that point you will probably need to replace the rotors anyway. Grinding the brake pad backing plate into the rotor will destroy it in very short order.


#11

Nobody turns rotors anymore.

First, the cost of turning a rotor almost equals the cost of a new replacement rotor.

Second, as mentioned turning rotors makes them thinner making them more suseptable to warping.

And third and more importantly, when the rotor is turned there’s no way that the proper finish will machined onto the rotor so the brake pads properly embed into the rotor. This then causes brake noise.

That’s why nobody turns rotors anymore.

Tester


#12

I’m in agreement with Tester about rotors seldom being turned anymore. It’s not a matter of not being able to; it’s a matter of economics.
Flat rate manuals often give about .8 to an hour to machine one rotor and that does not include the labor charge or removing and replacing it on the vehicle. Multiply that hour X the shop flat rate and it’s often more than the cost of a new rotor.

There are 2 ways of turning rotors also. One is the quick and easy method. The other is the much slower and correct method.
Many people who turn rotors believe the best method is to set the lathe on FAST, dial in about .020 cut on it in one shot and have at it. This is not the correct method.


#13

Sometimes I will find new drums or rotors in the box with the kind of machining you are talking about, ok4450. This is especially bad with drums and I will often machine .002-.005 off of a new drum before installing it. The first test drive with outrageous vibration and shoe slap was enough to make me do this before installing any new drums that had a rough or threaded finish.


#14

The dealer is talking about replacing worn parts, while the regular mechanic is actually suggesting you wear the part a little more, which you don’t want to do. I guess the mechanic has the equipment to turn rotors and it’s not getting a lot use these days. I side with the dealer.

The reason you want a certain amount of thickness in your rotors is that the rotors absorb most of the heat created during braking, and dispels that heat into the air while you are not braking. Rotors are heat sinks. Brake pads are composed of materials that tend not to absorb heat. Depending on what kind of roads you travel, this can either mean very little to you or become a life and death situation. If you tend to brake very little, and for short periods, on relatively flat roads, rotor thickness is not so big a deal. If you routinely travel very steep roads (downhill) and need to use lower gears and need to brake frequently and for long periods, you want nice thick rotors and pads. Very hot rotors cannot provide enough friction to slow a vehicle on a steep decline.
I get it that you mean by your question, do you need to turn or replace the rotors if they are not scored but are getting thin. The answer is no to turning the rotors. Rotors are cheap enough to just replace them new if they worn or rusted or warped, less than $100 for a pair. The answer is yes to replacing them if they are thin. Since you are asking about rear brakes, one thing to check is whether your emergency brake is holding the car in place on an incline while the car is in neutral. You need that to pass inspection.
The other (more important) reason you want to replace them if they are too thin is that the rear brakes need to work just as well as the front brakes in order to ensure even braking front and back, which prevents the front brakes from engaging the ABS too soon during sharp or wet braking.

In most cars, the rear rotors are the easist to replace, but you have AWD, so I guess that the replacement will be as much work for you as the front rotors would be. But if they don’t seem as important as the front rotors, be assured they are worth the effort and extra cost. Rear brakes need to work in concert with the front brakes.


#15

Thanks Joseph; I’m slowly coming around to the idea of just replacing them when I do a brake job. That’s what we did on my wife’s car with 110,000 miles on it. It still had the original rotors (my wife brakes carefully!), and it was only the second brake job.


#16

Ask your mechanic to inspect your rotors including measuring the thickness to compare to new. If the rotors are not significantly worn, are not deeply grooved, your brakes do not pulsate when applied at high and low speeds, the swept surfaces on the rotors are not reduced by winter salt corrosion and the vehicle stops without veering to one side, you can run with your old rotors. Shallow rotor grooves are harmless but take it a easy at first to let new pads bed into the shape of lightly grooved rotors.

I change my pads when the friction material is about the same thickness as the metal backing.

It is the policy of pro mechanics to either turn or replace rotors whether needed or not to reduce the possibility of a comeback complaint. It’s easy insurance for them at an additional cost for you.

I have the original rotors on a car with well over 200,000 miles. That is only one example but demonstrates that rotors can be reused without machining them.