Question for Mechanics and Oppos with opionos!

"Meatcoma" (mastapoof) 11/05/2014 at 16:42 • Filed to: Rotors, turning rotors, new rotors

1

54

While I realize the lead pic is not able to be turned, why is it that no shop will turn rotors any more? I've had multiple places that state the metal is too thin to turn. Is this because the rotors themselves are being made thinner or is this just a way to skirt liability and get you to purchase new ones.

Back in the day I remember I used to get a rotor turned at least once before I had to replace them. Anyone know exactly why this is impossible nowadays?

ly2v8-Brian > Meatcoma 11/05/2014 at 16:43

2

Not worth the effort, generally.

MontegoMan562 is a Capri RS Owner > Meatcoma 11/05/2014 at 16:44

2

maybe yours wore down to far before trying?

Party-vi > Meatcoma 11/05/2014 at 16:45

3

Why can't you turn this?

Shankems > Meatcoma 11/05/2014 at 16:45

4

Rotors are cheap, the customer isn't coming back with any pedal judder, and liability is scary.

ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) > Meatcoma 11/05/2014 at 16:47

1

Bit of both I suspect.

I had to tell a parts store to turn my rear rotors when I had to do my rear brakes. I looked up the specs before I went so I knew what the tolerances were. They initially did not want to turn them, but I told them the specs and one turning was not going to put the below safe clearances. I also told them I knew the rotors were installed new and had not been turned previously which I think helped them feel better about doing it for me.

505Turbeaux > Meatcoma 11/05/2014 at 16:48

1

my machinist has specs on everything up till new. There just isnt the metal there anymore to turn. Car manufacturers are fucking cheap these days. Just enough metal to get you to warranty is done

bradleyjames518 > Meatcoma 11/05/2014 at 16:49

1

Replacement rotors are cheap and turning only solves the problem for a short amount of time. They warp again because they can't dissipate the heat as well.

crowmolly > Meatcoma 11/05/2014 at 16:49

2

Auto stores stopped training people how, and they don't have to keep the machine on hand. More stock room and less knowledge needed by workers.

Go to sleep, I'm a Clown > Meatcoma 11/05/2014 at 16:50

2

Low tech ABS right there.

DailyTurismo > Party-vi 11/05/2014 at 16:55

9

Okay. No problem. I turn for you.

RazoE > Party-vi 11/05/2014 at 16:55

0

WHY DIDNT YOU TURN...?!?

BmanUltima's car still hasn't been fixed yet, he'll get on it tomorrow, honest. > Party-vi 11/05/2014 at 16:55

1

There's plenty of metal there!

Alfalfa > Meatcoma 11/05/2014 at 16:58

1

Former machinist here. It's a combination of things, really. First off, rotors are being made cheaper/thinner. Older rotors that can hypothetically be turned have probably already been turned as much as they can take. (Which is usually only once). So there's that, and the possible liability that comes with it. Parts stores are staffing people to turn them less and less, because they don't want to train people and most machinists can find a better job than just turning rotors day in and day out, and working a parts counter on the side. For these reasons, a lot of places won't even touch them.

'Wägen, EPA LOL > Meatcoma 11/05/2014 at 17:01

2

Not enough material on them anymore; plus the replacement part is cheap. Why bother turning when you can replace.

All conjecture below this:

Not sure if anyone else knows better on this, but if cooling vanes have become more and more prevalent over the years: first, this would make the rotor dissipate heat better and lead to less warping, reducing need to turn a rotor; second this makes the rotor wall thinner on new rotors while older rotors would be thicker to decrease the likelihood they warped but the added material also meant that there was something there to turn.

Mr. Ontop, No Strokes, No Smokes...Goes Fast. > Meatcoma 11/05/2014 at 17:01

0

Could someone explain what it means to "turn your rotors?"

JGrabowMSt > Meatcoma 11/05/2014 at 17:02

3

No money in it, primarily really. There's also a degree of uncertainty with the cheap shitty parts on cars today.

From the techs point of view, if they did turn the rotor correctly, but the rotor cracks once the customer has it back for a couple days, well, the shop did a shitty job in the customers point of view. If the shop just puts new rotors on, the parts have a warranty, and if the part fails, then it's covered. The shop doesn't have to spend the time doing the job twice, only once. While most consumers don't exactly listen to it, when getting parts, they'll say whether it's only parts or parts and labor are covered by any warranty. This is more of the big items like a motor or transmission, but shops do whatever possible to retain their credibility, and if that means the customer pays $30 extra for brand new rotors when the old ones were technically "good enough," then they have that $30 in their pocket, and if the new part fails, they don't lose as much time on payroll having to repeat jobs.

That and cheap parts can split or crack far easier. Porsche drilled rotors? My neighbor goes through them often. The rotors develop cracks in them by each of the drilled holes. He gets a handful of track days out of it, and then the rotors are junk. Even a little crack is the kiss of death on those rotors, because a chunk coming off can cause some wicked damage.

So in short, liability and time. Putting on new rotors is minutes. Turning a rotor is more than just minutes, and can be messed up pretty easily by an inexperienced tech that never learned the correct way to not only turn the rotor, but double check everything afterwards.

EL_ULY > Meatcoma 11/05/2014 at 17:04

1

Some cars are replace only (lipped edged design)

Some can be cut but if at minimum specs, they cannot be done. Sometimes they are too warped that by the time you get it clean, they are too thin

EL_ULY > Mr. Ontop, No Strokes, No Smokes...Goes Fast. 11/05/2014 at 17:07

2

One rotors are broken in, they are reflective because the pads and rotor surface are being worn in. When it's time to replace pads, it is recommended to put rotors on a lathe to removed the shiny surface into a semi rough exposed steel surface. This is so the fresh brake pad and rotor can both seat properly.

mcseanerson > Meatcoma 11/05/2014 at 17:07

1

My local O'reillys will do them for $8 a pop.

EL_ULY > ly2v8-Brian 11/05/2014 at 17:07

1

not difficult at all to do. New rotors are most times cheaper

InRatMartin > Meatcoma 11/05/2014 at 17:08

0

Do they refuse point-blank or try talking you out of it?

Meanwhile, back in R of SA, customers often insist on a skim. I allow that to happen, if the brake disk (rotor) is still in good nick - no cracks or chipmarks and above the wear limit. If ridges are involved, they're a handy indicator of how close the disks are to the wear limit. If the disks are fairly new but warped, (up to about 10k km), there should be enough meat left to straighten the disk.

It should never be done on cracked disks (even superficial ones), for that indicates overheating. Skimming (or as you call it, turning) will make it even more susceptible to overheating (the problem that brought them here in the first place), leading to the same problem recurring within a few thousand kilos. It should also not be performed when the disk is at or under its wear limit. Replace...

BZiel > Meatcoma 11/05/2014 at 17:14

4

We still turn rotors in our US shops and also here in Germany, but not very often, for a few good reasons.

First, the prices of new rotors are so low that charging someone $25 to turn one and only get another 10-15k miles out of it before it will have to be replaced vs. $40-60 for a new one makes the choice a no-brainer to most customers.

Second, yes, the construction is getting thinner, so there is much less steel available to work with and still stay within the minimum thickness guidelines after turning. Once you've grooved a rotor on almost any post 2000 car you're looking at a 80%+ chance of needing a new one. Also, we will not turn them to minimum thickness specs and just put them back on the road because we don't want the liability if they fail.

Third, many manufacturers today specifically instruct repairers NOT to turn rotors under any circumstances, especially on newer cars, and advise that doing so may void a customers potential warranty claim.

Hope this helps.

Takuro Spirit > mcseanerson 11/05/2014 at 17:16

1

I once bought rotors for $14 each, for the back of my Talon.

RamblinRover Luxury-Yacht > mcseanerson 11/05/2014 at 17:17

1

My local O'Reilly just did a set for me - $12 a pop. Half the cost of new rotors, but the difference between new size and minimum safe is apparently tiny - only barely enough room to get new pads in (after expansion) with rotors that were turned to only just above minimum.

RallyWrench > Meatcoma 11/05/2014 at 17:45

1

It's very often more cost & labor effective for shop and customer to buy new ones. Turning rotors properly requires multiple passes on each, which takes time. For the increase in labor costs, we can often supply OEM-quality new rotors.

We have a brake lathe, but rarely use it anymore. Some cars, like many BMWs in my experience, are very sensitive to the amount of rotor material remaining. If turned, the rotors are much more likely to develop runout or noise issues than a new set is because less material=poor heat dissipation=improper material transfer between pad & rotor=runout variation=vibration=unhappy customer=warranty repair.

Clay_T > Meatcoma 11/05/2014 at 17:51

1

All good answers here...

I deal with rotors two ways when doing brake jobs.

For rotors on hoopties:

I just use them, unless they are grooved beyond recognition. Anything less than ~2mm grooves is minor.

Take them off and sand the piss out of them with some 100 grit emery cloth to remove all the old pad material and knock down the high spots. Reinstall with new pucks and bed them in good. Done...

Non hooptiess are pretty much the same deal except I'll get new rotors the second time I do the hooptie brake job. By then the rotors are approaching the minimum thickness (down in the gouges, anyway).

That whole shimmy shimmy shake shake warped rotor thing that sends folks off to get their rotors turned usually has nothing to do with the rotors being warped.

Most of the time it's uneven distribution of pad material around the rotor.

Many times, simply going through the bedding process again will clean them up... If you can stand the shaking until things get hot.

Or just sand them good then bed again.

biker > Meatcoma 11/05/2014 at 17:57

3

several places around town turn them, but as many have commented it isnt worth it, not for the difference in cost, & safety.

now I will comment to tell you what almost isnt done anymore, cam grinding brake shoes! anyone know anything about?

well when you put new brake shoes on a vehicle with drum brakes, most of the time they are not a true correct fit. especially if the drums are for an older 60's vehicle & may have been turned 1 or more times before which makes the outside diameter larger. so when you put new shoes on it & try to stop you dont have good brakes, it takes quite a few stops to wear off the brake material to the point where the whole shoe is making contact correctly. so when you cam grind shoes, your removing brake material to make the shoe fit the drum & not need much of a breaking in time.

however the cam grinding phased out with most cars having disc brakes, as well as older brakes being made of asbestos, which worked great, I still have some asbestos brakes for old VWs, in todays times even a vehicle with a drum rear & disc front you wont notice the brake wearing in, however do a brake job on all 4 wheels on older full sized 4 wheel drum brake car, & dont cam grind & try to do a panic stop in first few miles, it will not happen!

bhardoin > Meatcoma 11/05/2014 at 18:01

1

While I was working in a tire shop we'd turn rotors all the time. If we did a brake job, we'd always check the rotor thickness with a caliper, match that to the factory spec, and turning the rotors was standard if you got new pads on it. But we'd always go by the book thickness, or if they were visibly damaged or really warped we'd recommend new ones.

ly2v8-Brian > EL_ULY 11/05/2014 at 18:14

1

that's what I meant. I've used a brake lathe before, easy.

shop-teacher > biker 11/05/2014 at 22:21

0

I learned something new today :)

biker > shop-teacher 11/06/2014 at 08:16

0

I did a search with bing, alot of people called it radius grinding. http://www.bing.com/images/search?…

I have actually had thoughts of picking up a machine to offer the service to old car guys, on some of the forums I am on. its not a big profit item, but would supply a need, and be a few dollars here & there.

I have seen some guys offer this service on some vintage forums, relatively cheap, shipping brakes would be more expensive.

Meatcoma > RamblinRover Luxury-Yacht 11/06/2014 at 09:35

0

So then I assume they are making rotors thinner?

Meatcoma > Mr. Ontop, No Strokes, No Smokes...Goes Fast. 11/06/2014 at 09:39

0

In most cases your pad does not cover the entire rotor and as the metal wears down on your rotor and material wears down on the pad from braking it can create a 'lip' on the outside edge(as well as EL_Uly's description). When they 'turn' a rotor they will remove that lip and make sure the wear is precise. Your rotors can develop a small warp in them, getting them turned sometimes will correct this and give you a factory finish on the rotor surface.

Meatcoma > BZiel 11/06/2014 at 09:40

0

Good explanation, thanks.

Meatcoma > JGrabowMSt 11/06/2014 at 09:40

0

Another good explanation. Thanks.

Meatcoma > 'Wägen, EPA LOL 11/06/2014 at 09:41

0

I can agree with this.

RamblinRover Luxury-Yacht > Meatcoma 11/06/2014 at 09:49

0

This was on a car now 20 years old. If the wear allowed was so low back then...

Meatcoma > MontegoMan562 is a Capri RS Owner 11/06/2014 at 10:18

0

I normally replace them before metal to metal lol

MontegoMan562 is a Capri RS Owner > Meatcoma 11/06/2014 at 10:19

0

haha, I should hope so, though that doesn't mean there's zero wear on the rotors.

Meatcoma > Meatcoma 11/06/2014 at 10:20

0

Some great answers! Thanks to all of you.

Meatcoma > RamblinRover Luxury-Yacht 11/06/2014 at 10:22

0

New pads have more material on them vs older pads as well.

Meatcoma > MontegoMan562 is a Capri RS Owner 11/06/2014 at 10:23

0

Cars eventually stop even with metal to metal!

I can say with certainty I have installed a pad backwards once.... maybe twice but that is all!

MontegoMan562 is a Capri RS Owner > Meatcoma 11/06/2014 at 10:24

0

you installed a pad backwards?!

really?!

RamblinRover Luxury-Yacht > Meatcoma 11/06/2014 at 10:25

0

True, but you'd think they'd stay within factory deviation. I guess the expectation is that they'll be used with new rotors that are undersize for turning after one go-around, but even so.

shop-teacher > biker 11/06/2014 at 10:59

0

I've never heard of it, but it makes sense.

Meatcoma > RamblinRover Luxury-Yacht 11/06/2014 at 11:11

0

Yea but I've replaced rotors that have never been turned and the pads haven't been changed. Maybe the quality of pads/rotors has something to do with it as well.

Meatcoma > MontegoMan562 is a Capri RS Owner 11/06/2014 at 11:13

0

Yea. so it literally was metal to metal. You know within like 3 ft.

MontegoMan562 is a Capri RS Owner > Meatcoma 11/06/2014 at 11:23

0

wow dude.

just wow

Meatcoma > MontegoMan562 is a Capri RS Owner 11/06/2014 at 11:28

0

I was young! I wanted to see how fast I could do a brake job. Needless to say it wasn't very fast once I had to break it down again and flip the pad.

MontegoMan562 is a Capri RS Owner > Meatcoma 11/06/2014 at 11:30

0

hahahahaha no, it definitely wasn't fast at that point

SidewaysOnDirt still misses Bowie > Shankems 12/19/2014 at 10:01

0

Exactly. Some small shops will still do it (needed to get my rotors resurfaced on my AW11 after a hub failure), but the corporate ones for the most part are interested in getting you in and out quickly and they don't want to have to do the work again for free.

SidewaysOnDirt still misses Bowie > 505Turbeaux 12/19/2014 at 10:03

1

You're also more likely to have vented discs these days, which might have something to do with less metal.

Drakkon- Most Glorious and Upright Person of Genius > Meatcoma 01/08/2015 at 09:08

0

Warping can come from many issues, but one is not dissipating heat effectively.

One of the easiest ways of dissipating is just having more mass to work with. But as others have said, rotors keep getting thinner and lighter. By turning the rotors, you have discs that are already in trouble, and they have even less of what you need (mass!). After turning, the warping comes back faster the second time.

wacopalypsenow > crowmolly 01/14/2015 at 14:46

0

less knowledge needed by workers.

Except for their extensive knowledge of fake chrome stick-ons and Lucas fuel additives..

If I get offered fucking Lucas snake-oil one more time...