machining rotors

[Donald]

Almost no one machines rotors anymore. But I had thought that the machined rotors had less metal and were more likely to "warp". But as we know, rotors do not actually "warp" people just say that. Basically the rotors become of non uniform thickness. Also when rotors are machines how much metal by percentage is really removed? 1% 2%?

So is the real reason why people do not machine rotors because the difference between new thickness and throw-away thickness is very small?

 

[Mopar618]

When the rotors are machined, you're basically just shaving off enough for everything to be equal to the lowest point. So technically, it varies per application.

A friend of mine that I do jobs with quite a bit is still holding on to his brake lathe at the moment, but he doesn't know how long he'll continue to keep it due to the fact that few customers want their rotors machined anymore. Some machine shops will charge about as much to machine a rotor as it would cost to purchase a brand new one.

 

[jeepman3071]

Originally Posted By: Mopar618
When the rotors are machined, you're basically just shaving off enough for everything to be equal to the lowest point. So technically, it varies per application.

A friend of mine that I do jobs with quite a bit is still holding on to his brake lathe at the moment, but he doesn't know how long he'll continue to keep it due to the fact that few customers want their rotors machined anymore. Some machine shops will charge about as much to machine a rotor as it would cost to purchase a brand new one.


Bingo. That is the problem around here.

 

[Hokiefyd]

Originally Posted By: Mopar618
Some machine shops will charge about as much to machine a rotor as it would cost to purchase a brand new one.


I agree that this is the problem, for most consumers. I prefer to buy premium rotors and get more life out of them, so I'm one of the few who actually does search out places that will machine rotors. O'Reillys Auto Parts advertises that they machine rotors, but I don't know the cost. Pep Boys does it for $15 each, and I've had them machine a number of rotors for me. $15 is far less expensive than a new premium rotor. I'd rather have a premium rotor that's been machined a few times than a new white-box special, origin unknown.

 

[scurvy]

There's so little amount of allowable wear on my rotors between 'new' and 'replace', quality replacement rotors made in the EU are amazingly inexpensive & there's zero downtime when I replace rotors with new.

I have access to a machine shop and could turn my rotors for free (i.e., the lathe, inserted tools, electricity are all paid for by someone else) but I never do. It's not worth the time & effort.

 

[Danno]

Originally Posted By: Hokiefyd
Originally Posted By: Mopar618
Some machine shops will charge about as much to machine a rotor as it would cost to purchase a brand new one.


I agree that this is the problem, for most consumers. I prefer to buy premium rotors and get more life out of them, so I'm one of the few who actually does search out places that will machine rotors. O'Reillys Auto Parts advertises that they machine rotors, but I don't know the cost. Pep Boys does it for $15 each, and I've had them machine a number of rotors for me. $15 is far less expensive than a new premium rotor. I'd rather have a premium rotor that's been machined a few times than a new white-box special, origin unknown.

Have you had a premium rotor machined a few times?
I am interested knowing more about the car, mileages turned and pads used.

 

[Donald]

Originally Posted By: Hokiefyd
Originally Posted By: Mopar618
Some machine shops will charge about as much to machine a rotor as it would cost to purchase a brand new one.


I agree that this is the problem, for most consumers. I prefer to buy premium rotors and get more life out of them, so I'm one of the few who actually does search out places that will machine rotors. O'Reillys Auto Parts advertises that they machine rotors, but I don't know the cost. Pep Boys does it for $15 each, and I've had them machine a number of rotors for me. $15 is far less expensive than a new premium rotor. I'd rather have a premium rotor that's been machined a few times than a new white-box special, origin unknown.


Aside from some non rust coating (and not talking slotted/drilled rotors) what does a premium rotor get you? An auto shop teacher at a local technical high school installed a premium rotor on one side and a normal quality rotor on the other side. After a year, they both looked and worked the same.

 

[Donald]

So the main point is that rotors from China are now so cheap that is does not pay for an American worker to machine them?

 

[JHZR2]

Originally Posted By: Donald
So the main point is that rotors from China are now so cheap that is does not pay for an American worker to machine them?


Wow, what an outlook. Sell another fellow countryman out for a few bucks.

My main issue is that I rarely wear out brakes. I drive in a lot of city and stop and go traffic, but I drive carefully, and so brakes just dont wear for 100k miles.

What fails first is some other stupid thing - the last one was one of the pieces that held the brake pad to the caliper - so the pad was a little loose.

I replaced my rotors with known first-world products for little extra money and had the knowledge that they were new. But my rotor hats were BADLY rusted.

Ive seen horrible rust inside the cooling vanes as well. Wouldnt be comfortable with rust in the structural area of the rotor (perhaps Im overthinking it).

 

[dparm]

Some cars just seem to chew up brakes faster. My dad's G35 is notorious for it -- extremely aggressive pads mean new pads and rotors every 20-30k.

 

[Carbon]

Many car brake job deals include turning the rotors in the price. Those shops would much prefer to sell you new rotors.

I suggest getting the specifications for your car's rotors, and ideally take a caliper/micrometer to the brake job with you. If you are not up to that, ask for the used parts back. I did that. I returned with the old rotors and a caliper. He said after turning there would not be enough, and offered to turn one to see. I took him up on that and I ended up a refund for the new rotors that were installed but not needed.

Some rotors will usually have plenty of material left at the time of a brake job, and those can be turned. Some cars typically do not have enough thickness available after having gone through one set of pads. It is worth checking.

Also, it is good to check the thickness on the old pads if the repair facility was the one that told you that your pads were in need of replacement. Modern cars have a noise maker that will sound off in plenty of time. I am not saying to always go down to that point, but it will not hurt. However having them say the spec is 2 mm (spec was 1 mm) and measuring 3.6 mm at the thinnest part of the old pads will cause me to be more attentive the next time.

 

[SwampSurvivor]

I've never warped or worn out a rotor.

I have had rust grooves in them so bad they would shake and wear the pads in a few thousand miles.

I have "resurfaces" a few sets with sand paper and angle grinder

 

[OneEyeJack]

An important part of a modern mechanic's job is to diagnose and change parts with the aid of modern sophisticated tools. When I first went to work as a mechanic in a neighbor's auto repair business I rebuilt engines, bored them out, honed the cylinder walls, surfaced the decks and heads, ground valves and seats, rebuilt water and fuel pumps, soldered and re-cored radiators, welded parts, cylinder blocks and cylinder heads, machined and milled parts and many other tasks that are almost unheard of today at your local automotive service garage. I went through training in the garage supervised by the owner. Every time I learned a new skill it was on to the next new skill. It's no surprise that re-surfacing rotors is no more when they can be swapped for new rotors. In the future brake rotors will probably be designed with built in hubs and wheel bearings installed to eliminate subtle problems that are hard for someone changing parts to figure out. Cars of the future will all probably become increasingly modular with more and more parts combined into replacement assemblies than need only be swapped with simple tools. The mechanic's job has completely changed and is a good fit for young people growing up with smart phones, tablets and the Internet. Soon your smart phone will be your connection between your car and your mechanic and you'll both be speaking the same language. If there's a problem your phone will tell you and will also be able to give your mechanic real time information to help him keep your car in top shape.

 

[SteveSRT8]

Originally Posted By: dparm
Some cars just seem to chew up brakes faster. My dad's G35 is notorious for it -- extremely aggressive pads mean new pads and rotors every 20-30k.


Exactly. This is a PAD issue, not a ROTOR issue. As long as the rotor meets the specs from your mfgr then iron is iron.

As Donald said wisely above, exactly what do you get with a so-called 'premium' rotor? Admittedly there is some real junk out there but most reputable parts houses aren't going to sell you a liability suit...

 

[Kruse]

Originally Posted By: Hokiefyd
O'Reillys Auto Parts advertises that they machine rotors, but I don't know the cost. Pep Boys does it for $15 each, and I've had them machine a number of rotors for me.


I think the O'Reillys near me charges $7 for a car rotor and $10 for a truck rotor. And it might be rare, but rotors DO warp, as well as being non-uniform.
I do all of my own mechanic work on my vehicles, but I was out of town and had a wheel bearing instantly fail on my Aerostar that wiped out my rotor. A shop that I had never done business with before put on a new rotor (along with bearings and a seal) and I was on my way. About two weeks later, I had a pulsating pedal. I instantly suspected the new rotor and I tried to take the wheel off with a cross wrench. I couldn't do it. I tried with a breaker bar and couldn't do it. I had to get a cheater pipe on a breaker bar to get the lug nuts off. (I'm 6'6" and 250 lbs. I'm no weakling) The "mechanic" had obviously turned up his impact wrench to full power when he put the wheel on.
Anyway, as I watched the rotor being turned, it was on obvious warp, thanks to his idiotic "repair" on my vehicle. Sometimes, they do warp.

 

[Rock_Hudstone]

Originally Posted By: Donald

Aside from some non rust coating (and not talking slotted/drilled rotors) what does a premium rotor get you? An auto shop teacher at a local technical high school installed a premium rotor on one side and a normal quality rotor on the other side. After a year, they both looked and worked the same.

Wouldn't want a tech working on my car trained by that auto shop teacher.

There is quite a bit of difference between premium rotors and the white box specials as someone put it.

A premium rotor is (or should be), almost identical in design, fin count and casting to factory, in addition to better metallurgy.

Although, as with many overseas made rotors, premium or not, I have my doubts about the metallurgy these days.

 

[Kuato]

Originally Posted By: Hokiefyd
Originally Posted By: Mopar618
Some machine shops will charge about as much to machine a rotor as it would cost to purchase a brand new one.


I agree that this is the problem, for most consumers. I prefer to buy premium rotors and get more life out of them, so I'm one of the few who actually does search out places that will machine rotors. O'Reillys Auto Parts advertises that they machine rotors, but I don't know the cost. Pep Boys does it for $15 each, and I've had them machine a number of rotors for me. $15 is far less expensive than a new premium rotor. I'd rather have a premium rotor that's been machined a few times than a new white-box special, origin unknown.


The labor is exactly the same, so the price difference is between cost of the rotor and the machining. I've found that if you take your rotors in hand to have them turned, that you can get them done for $15-20 each.

 

[dparm]

Originally Posted By: SteveSRT8
Originally Posted By: dparm
Some cars just seem to chew up brakes faster. My dad's G35 is notorious for it -- extremely aggressive pads mean new pads and rotors every 20-30k.


Exactly. This is a PAD issue, not a ROTOR issue. As long as the rotor meets the specs from your mfgr then iron is iron.

As Donald said wisely above, exactly what do you get with a so-called 'premium' rotor? Admittedly there is some real junk out there but most reputable parts houses aren't going to sell you a liability suit...




Just a better warranty, that's all.

 

[Donald]

Originally Posted By: Rock_Hudstone
Originally Posted By: Donald

Aside from some non rust coating (and not talking slotted/drilled rotors) what does a premium rotor get you? An auto shop teacher at a local technical high school installed a premium rotor on one side and a normal quality rotor on the other side. After a year, they both looked and worked the same.

Wouldn't want a tech working on my car trained by that auto shop teacher.

There is quite a bit of difference between premium rotors and the white box specials as someone put it.

A premium rotor is (or should be), almost identical in design, fin count and casting to factory, in addition to better metallurgy.

Although, as with many overseas made rotors, premium or not, I have my doubts about the metallurgy these days.




The auto shop teacher is quite knowledgeable, had his own shop for years and a college teaching degree. The rotors he compared were a "normal" one from NAPA and a premium. Normal is what he uses most of the time for customers when he had his own shop. He did not set out to find the cheapest Chinese rotor possible at Big Lots.

 

[Ken2]

Iron isn't just iron. There are different grades and qualities of cast iron. I don't know if any rotors get any premium grades of cast iron. There are different alloys of cast iron with various carbon and silicone contents and possible alloys with nickel, chromium, and molybdenum to increase hardness. Certain casting techniques result in a harder surface. The cast iron can be aged or heat treated for stress relief. Or, none of the above.

I saw an example of "high tech" cast iron at a diesel engine factory in Switzerland where I trained. The Swiss are a very proud people, and the Swiss at this factory admitted that they did not know how their Japanese licensee could produce cast iron cylinder liners with longer service lives than the Swiss could figure out.

So--premium cast iron brake discs are possible. Whether the rotors sold as such actually are better or just higher prices and perhaps a longer warranty might be another story.

And, we know that a vehicle with a lighter unsprung weight will handle better, and lighter rotating assemblies will brake better and accelerate better. Lighter, skinnier brake discs will perform better and cost less to make. And they'll have little or no extra material to allow for refinishing.