Brake rotors, machining / turning

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I'm having issue with run-out!

Typically I do not put a run out gauge on turned Rotors or new OEM. But decided to in this case, on just one to start with. Well ended up put run-out dial gauge on all. Procedure is to remove rotor and turn to new position on hub, if out of spec, or just wanting to hit the sweet spot (closes to zero). This is time consuming to say the least.

I just had a near new set of NAPA rotors turned. I would never buy these myself for a 100 series. But since they were install by PO less than 2k miles ago along with NAPA pads, by Midas. I decided to replace PADs with OEM and just have the rotors turned to make sure true and had good bedding surface for new pads. I did not do a good run-out inspection beforehand. Other than, just put dial gauge on 1 front rotor. Found it out of spec, without really marking each few degrees, to get a good reading. I saw hot spot, imperfection along with bed in rust in spots. So just had all turned.

What I found after have machine turned off vehicle. Was all rotor out of spec. With rears I did remove each rotor from hub and turn to all 5 position. Closest I could get was 50% above max limit out of the spec.

Each side rotor run-out was near the same, more out on rears than fronts. But pattern the same. I'd get 0.00 mm (zero) for about 20 degrees of 360 degrees. Than as I continued to turned rotor 360 degrees. Run-out would start increasing form zero to peak of ~0.25 to 0.27mm at ~ 180 degree point of 360 degrees of disk surface. Than start dropping back to zero as I continued to turn to starting point. Very symmetrical pattern from one side to other side of vehicle, numbers near a match also. Also ran up back side rotors (back disk), which matched front disk (opposite numbers).

Now since they're all freshly turned, it cannot be uneven deposits of pad material or uneven metal surface of disk right!

So questions I have:
Is the brake lath in need of calibration?
Is it's attachment to hold rotors in lath issue?
Is it lathe operator error?
Is it the rotors themselves, can't be trued-up as axis is off?
Or what?
 
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awesomeissquid

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Is it your brake lathe or are you taking it to a shop? If its yours there is typically a way to check for and correct runout to true the system up. If it is a shops lathe, I would assume they are maintaining the equipment. If the lathe is running true then it should be machining the rotors true to the mounting surface.
 
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No It's a brake lathe at a parts store where of the two guys are trained on it. I asked them if it had been calibrate, they had know idea. The manager of the store is have manufacture come in and calibrate. Or so he said he call them. They had just moved from another local (the whole store) and bough lath with them. It's been in use for over a decade that I know of.

I felt the same. That lathe should take out warp-age and true up rotor disk to hub relationship!

But what if at center hub mounting point, relation to disk is off by ~.5 degree due to poor manufacturing rotor? Rather than the axis of lath set up or calibration. Then could it be fixed into a calibrated lathe dead -on. But off center without hope of turning? My thinking has been lathe would center mount point to true up disk. But perhaps my thinking was/is flawed? (More than usual..LOL)!


Useless info to conversation:
I had another machine shop near them, turning for me. Machine shop suddenly closed. Young couple bought the location and turned into a Auto repair shop. They had kept the machine shop's brake lathe and did turn my rotors. Man did this guy, now independent mechanic, did do great job. He used diamond non directorial bits. Really took the time needed to get perfect. Even marked the thickness and run out on finish rotors. They charged me double any shop/parts store would. But I gladly paid extra for good job. Unfortunately they became to busy to take on the extra work, unless I pay shop rate for time. Which is about $120 per rotor. I totally understand, but can buy OEM new for that!
 
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ramangain

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isn't that about the same cost as new rotors though? I quit turning rotors years ago and started replacing instead.
Start a new sport ... brake disc golf. Aim to replace those flimsy frisbees on every college campus! They say the aggregate population is getting more overweight and out of shape; this should help. Maybe apply for a NIH grant?

#sharktank
 

hoser

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I did Dealership $90 each rotor.
Eek.. yeah, that is no bueno. It would probably be the fix but finding the root of the cause is a lot more fun (and expensive!). :) I also don't turn rotors anymore. Run them as is or replace.
 

flintknapper

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If the rotor were mounted off axis or had been badly warped...then it should show up as different thicknesses in the rotor (about its circumference). Measure with a pair of calipers in different spots and compare. Ideally, turning rotors should be only to remove scoring or a lip that has formed. Not to 'true' the rotor (though a small amount is permissible).
 

abuck99

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Start a new sport ... brake disc golf. Aim to replace those flimsy frisbees on every college campus! They say the aggregate population is getting more overweight and out of shape; this should help. Maybe apply for a NIH grant?

#sharktank
They make good tent tiedowns
 
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isn't that about the same cost as new rotors though? I quit turning rotors years ago and started replacing instead.
Yeah and new OEM may be way I go. The advantage of on vehicle is grind, frt hubs (bearings) don't need pulling apart. They also say it gives the truest turn.
Eek.. yeah, that is no bueno. It would probably be the fix but finding the root of the cause is a lot more fun (and expensive!). :) I also don't turn rotors anymore. Run them as is or replace.
Yeah, very pricey. I always turn, with some exception. Like very good rears. For now I'm running as is.

But trying to understand if this happened. Is it bad manufacture of cheap NAPA rotors? (i'd never buy). Or is this issue with Shop's brake Lath?

I have about one set of rotors turned each month. Shop is having it's lath looked at now, by manufacture. Said they'd pay to have mine done elsewhere. But labor and time to pull is issue. On vehicle save me the time. But I really don't want to hit shop for that cost (they've been good to me)

If the rotor were mounted off axis or had been badly warped...then it should show up as different thicknesses in the rotor (about its circumference). Measure with a pair of calipers in different spots and compare. Ideally, turning rotors should be only to remove scoring or a lip that has formed. Not to 'true' the rotor (though a small amount is permissible).
I found a spec I call, T8 .02mm. Measurement taken at 8 point spaced evenly around disk. Max allowable 0.02 difference. In this case I did not do T8.

I did run-out back side of disk. Run-out match front to back, just opposite as should be.. Which indicates T8 is in spec.

FSM states: Replace or grind "On-car brake lath" if run-out out of spec.

Brake rotor disk front.JPG

I didn’t think you could do this with FT 4WD
I had on vehicle grind done once on my 01LC, at my Local Toyota Dealership ~18 years ago. They did a supper job. Front brakes lasted for 90K miles, rear 45K. Wear was very even on all pads and rotors still looked good.

If done right it is the best. It takes out some of the axle hub and wheel hub variation.
 
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flintknapper

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I found a spec I call, T8 .02mm. Measurement taken at 8 point spaced evenly around disk. Max allowable 0.02 difference. In this case I did not do T8.

^^^^

Paul are you saying .020" (Twenty Thousandths) here or something else?

I ask because the manual only allows for a bit under Three Thousandths (.0028")
 
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^^^^

Paul are you saying .020" (Twenty Thousandths) here or something else?

I ask because the manual only allows for a bit under Three Thousandths (.0028")
I stated in MM. Front run-out limit is .07mm, rear is .10mm

The T8 as I call it, is noted as 0.02MM in my notes. Don't recall where I found that back some years ago. In fact while I was doing this particular run-out a few days ago. I looked for where those numbers came from, but did not find (yet). But like I said, I did not do the T8 measurement. T8 is variation thickness from back to front. Just run up both back & front side on my run-out dial gauge.

What I do; Is write measurements on the front of disk as I'm turning disk. Then I switch gauge to back side of disk and run again. This time writing on outer edge. This gives run-out of front and back sides disk. If they're not equal and opposing, I'd than do a T8. They were equal and opposing. So I did not check T8.

For rear, I mark axle hub with #1, at point e-plug hole is aligned to. Than remove lugs (Started w/3 lugs on, than had all 5 on at 76ft-lbf) and pull off and turn rotor 1/5 turn. Torque on lugs and run-up on dial gauge again. Mark axle hub as #2. I keep removing and turning, note of highest reading at each 1/5 turn. Then place rotor on number mark that had lowest reading. Those giving me lowest run out possible.

These picture are after test done, and after caliper put back on. Test is done caliper off, so I've space to put gauge on back. If you could see under caliper, it's my zero marks, just about same width of caliper, which isabout 20-30 of 360 degrees surface area. Both side (LH & RH) had near identical pattern.

5 = .05mm. 10 = .10mm, 20 =20mm run out from zero point. This is LH side.

IMG_1560.JPEG

RH rear the marks are now to worn from my wiping with de-grease to read in picture.

IMG_1562.JPEG


Here's a LH frt where I used the point 0.00mm, some spots others not, like you can see .10mm., .08, 7 = .07.

IMG_1567.JPEG

RH frt
RH frt.jpg
 

flintknapper

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I stated in MM. Front run-out limit is .07mm, rear is .10mm

The T8 as I call it, is noted as 0.02MM in my notes. Don't recall where I found that back some years ago. In fact while I was doing this particular run-out a few days ago. I looked for where those numbers came from,

That's the measurement I was wondering about.....because I had never seen it referenced anywhere and thought maybe it was a misprint.

.02mm is significantly less than .001" and that would be a hard amount to detect without some really accurate tools.

I have to admire your dedication to getting things right. Good job.
 
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Well, I don't know I've got this right, but thanks!
This T8 (as I call it) has somewhat taken away from what I'm trying to figure out.


What I'm after here. Is this excessive run-out:

Brake lathe issue?
Or
A manufacture of rotor issue, one that a lathe can't correct?
 
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Some may find this interesting: On vehicle rotor machining.

One particular 06LC restore I did, "Snowy". I offered the buyer, to do a brake job while front wheel hubs off doing a wheel bearing service. I like having rotor turned and install new pads, if pads don't look like they'll make to next (30K miles) wheel bearing service. That way I can have rotors turned on a lath. He declined my offer. Said he could just slap in pads in his driveway. As I rule I don't just slap in pads, especially on front rotors. Rotors would have to spec out perfect, even the T8.

Vehicle history showed, a local INDY Toyota shop installed aftermarket rotors and OEM pads. I spoke to shop on there're choice of parts. They said they have issue with aftermarket pads, but not aftermarket rotors. I feel just the opposite is true.

Once I had "Snowy" ready for deliver, I test drove. My test drive was over 300 miles, up and down mountain passes. With some very long down hill stretches. I had no issue with anything. Brakes worked just fine. But Snowy's new owner did have steering wheel pulsing back and forth issue. Dang, why did he have issue with steering and not me on test drive. He sent me below video.


I notice in the video, RPMs low and MPH dropping. Also brake lights, from vehicle in front of him. I asked; "are you using brakes to control down hill speed"? He said YES!

I spoke with Toyota front end specialist, a master mechanic at my local Toyota dealership. Showed him the video. He asked two question:
1) Were brakes hot? YES!
2) Were these aftermarket rotors. YES!
He said they have a lot of issues with warped aftermarket rotor, when hot. We can debate all day what warped means, but save that for later.

Well, I drive using transmission to control down hill speed. It's just second nature to me, since I've driven in the Rocky Mountains all my life.
Snowy's new owner is from the east coast (flat lander), where driving style is different. So he was unfamiliar with engine/transmission braking.

So I suggested he take Snowy to Dealership and have "on vehicle brake rotor disk grinding". He did, and issue went away.
 
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flintknapper

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Well, I don't know I've got this right, but thanks!
This T8 (as I call it) has somewhat taken away from what I'm trying to figure out.


What I'm after here. Is this excessive run-out:

Brake lath issue?
Or
A manufacture of rotor issue, one that a lath can't correct?

Or both. Hard to know. Its a wonder it isn't more of a problem than it is....when you consider how critical the relationship of the parts must be.

A perfectly straight rotor will show 'run out' if mounted to a hub that is out of spec. All it would take would be some rust/debris between the mounting surfaces. I know you are fastidious about having things clean and right....but your average mechanic/shop could give a damn and want to move as many vehicles through the place as fast as they can.

Proper torque of the rotor to the hub (where applicable) needs to be done. If wheel bearings are loose or untrue the whole assembly will contact the brake pads continuously. Likewise the entire assembly will run untrue to the spindle. Lots of potential pitfalls once the whole assembly is mounted.

But your question involves just the rotor itself and how it might turned unevenly on a Lathe (which is certainly possible). If the technician didn't clean the back of the rotor, if the machine is old, if not centered correctly, properly tightened, vibration damper used...etc.


Your Local parts store tech is unlikely to take the care this guy does:




If you're lucky.....probably get something more like this:


 

Njck22

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I’m spoiled with cheap local dealership parts, at 65$ For oem fronts or 85$ for rear it’s not even a question.

maybe once I have 4 pairs a machine shop will cut me a deal to surface. Otherwise, iron is pretty easily recycled right?
 
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If the rotor centers are not fitted properly to the cones of the brake lathe, the rotor can be machined on an angle with respect to the hub face. This can be prevented by checking the run-out off the hub area of the rotor before machining. In case of improper chucking, you will only find a single high and low spot as the hub face and rotor face will be on non-parallel planes. From the pictures it looks like they is wavy pattern: multiple high and low spots.

You can start by checking the run-out of the wheel hub. For the rear, check the face of the hub without the rotor. Since small deviations get amplified by the rotor diameter, you want to make sure it runs perfectly true. Because the fronts are unique for these cars, you can check it with axle hub and rotor combined.

If the hubs do not run true, the rotor will not run true either. This is what an on-brake vehicle lathe is designed for. It will make the rotor run true, regardless of hub run-out.

Were the front rotors machined with the axle hub in place? From the pictures it looks like the high spots coincide with the 5 mounting bolts of the axle hub? Is there a chance that the rotor is deformed by bolting it to the hub after the machining?

Other reasons for wavy surface can be ringing during machining. From the surface finish, it does not look like that is the case.
 

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