Rotors

[Kenm3.3tt]

What mileage were you at when you first got your rotors resurfaced? I'm currently at 30k and feel a small lip on the edge.

 

[HerbieTheCar]

Getting new front rotors and brake pads at 31k miles.

 

[ScottFree]

Hmmm how can I put this delicately?
The short answer: It ain't broke, don't fix it.
The long answer: I haven't had a rotor turned in almost 20 years. It is no longer economically justified. There are a couple of reasons for this. First, "back in the day" of early disk brakes, rotors tended to be overbuilt for a number of reasons. They had a lot of "meat" on them (ie extra metal). This has radically changed as governments mandated better MPGs and people expected better handling cars. Reducing the weight of the rotors is an easy way to accomplish both of these. Reduce the weight of anything between the road and where the suspension attaches to the car (the "unsprung weight") generally improves handling. You reduce the rotor weight you can then also use smaller wheel bearings and lighter control arms and smaller springs etc etc... all this reduces the weight even more. That improves fuel mileage and handling and reduces cost. It's a win win win. Ok, class dismissed. There just isn't any extra "meat" on a modern rotor. Rotors in general should last 60-70K miles depending on your driving style and the amount of stop/go traffic. At this point they will not be reusable or turnable because to do so will generally make them too thin to be safe (there is a manufacturer minimum thickness) They will have to be replaced. Your rotors are about halfway there. The lip is a result of normal wear and tear. If you are very concerned about this, remove the rotors. The minimum thickness will be stamped on it somewhere. Using the appropriate "pointed tip" micrometer measure the thickness of the rotor in the deepest surface groove on both rotor surfaces. Using these numbers calculate the thickness the rotor will be after it is machined. Compare that to the minimum thickness number. Make the appropriate judgement call considering how much metal you will lose in resurfacing. Will you exceed the minimum thickness? If you double the amount wear at 30K miles this would be a good indicator of how much wear to expect at 60K miles. Does it make sense to remove metal now or just wait another 30K miles knowing that you will have to replace them in either case. Any decent brake shop has the tools and can do this math. Resurfacing one rotor generally runs $40 - $80. That is if you remove them from the car yourself and bring them in. You are also going to need new pads for those shiny rotors at additional $$. New rotors from RockAuto are about $50. Kind of a no brainer if you ask me.

 

[Yeti]

You mention rock auto. I am a big fan but wonder why they are much less expensive than my local auto parts store. Ordered all four rotors and pads for the boys Subaru $180 including shipping and tax. My local parts stores were over $350 Any idea?

 

[AnalogMan]

Front rotors resurfaced at 9000 miles. Brake pulsation started around 4000 miles. The front rotors had a run out from 29.8 mm down to 28.6. They were both resurfaced, right front down to 28.4 and left front down to 28.3. Both rear rotors were fine, within spec.

In over 45 years of driving and having owned dozens of cars with disc brakes, I've never had rotors get warped so quickly.

I hear you about modern cars not having any excess on the rotors to allow resurfacing. A friend with a BMW told me it's not recommended to resurface the rotors on his car, but to replace when needed. Even though only 1.5 mm of material was removed from my rotors, I sense for a brake disc that's a lot. I'm wondering how close to the limit they are now.

I don't need a crystal ball to see new rotors in my near future. But they won't be OE Kia parts.

 

[oddball]

Most parts stores around here won't resurface anymore. They say "the machine is broken", but really they either just don't want to mess with it, or no one is left that remembers how to do it. But yeah, it's usually not worthwhile anymore.

You mention rock auto. I am a big fan but wonder why they are much less expensive than my local auto parts store. Ordered all four rotors and pads for the boys Subaru $180 including shipping and tax. My local parts stores were over $350 Any idea?

Funny, isn't it? Usually shipping causes things to more-or-less equal out. e.g., a single item + shipping at rockauto is about the same as the item at the store, so buying in bulk or getting an assortment of stuff from the same warehouse is where you save money. Rotors have been the exception. My expectation is the store markup for their transport, storing, handling, etc is just higher. All store brands are likely Centric or one of the lower tier manufacturers.

 

[Kenm3.3tt]

Hmmm how can I put this delicately?
The short answer: It ain't broke, don't fix it.
The long answer: I haven't had a rotor turned in almost 20 years. It is no longer economically justified. There are a couple of reasons for this. First, "back in the day" of early disk brakes, rotors tended to be overbuilt for a number of reasons. They had a lot of "meat" on them (ie extra metal). This has radically changed as governments mandated better MPGs and people expected better handling cars. Reducing the weight of the rotors is an easy way to accomplish both of these. Reduce the weight of anything between the road and where the suspension attaches to the car (the "unsprung weight") generally improves handling. You reduce the rotor weight you can then also use smaller wheel bearings and lighter control arms and smaller springs etc etc... all this reduces the weight even more. That improves fuel mileage and handling and reduces cost. It's a win win win. Ok, class dismissed. There just isn't any extra "meat" on a modern rotor. Rotors in general should last 60-70K miles depending on your driving style and the amount of stop/go traffic. At this point they will not be reusable or turnable because to do so will generally make them too thin to be safe (there is a manufacturer minimum thickness) They will have to be replaced. Your rotors are about halfway there. The lip is a result of normal wear and tear. If you are very concerned about this, remove the rotors. The minimum thickness will be stamped on it somewhere. Using the appropriate "pointed tip" micrometer measure the thickness of the rotor in the deepest surface groove on both rotor surfaces. Using these numbers calculate the thickness the rotor will be after it is machined. Compare that to the minimum thickness number. Make the appropriate judgement call considering how much metal you will lose in resurfacing. Will you exceed the minimum thickness? If you double the amount wear at 30K miles this would be a good indicator of how much wear to expect at 60K miles. Does it make sense to remove metal now or just wait another 30K miles knowing that you will have to replace them in either case. Any decent brake shop has the tools and can do this math. Resurfacing one rotor generally runs $40 - $80. That is if you remove them from the car yourself and bring them in. You are also going to need new pads for those shiny rotors at additional $$. New rotors from RockAuto are about $50. Kind of a no brainer if you ask me.

So does rock auto sell the OEM parts? Thanks for all the info

 

[Kenm3.3tt]

Getting new front rotors and brake pads at 31k miles.

Gonna do the same. thanks bro