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is on car rotor cutting the best method? #5295560 12/16/19 12:37 AM
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WhyMe Offline OP
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watched a few vids about on car rotor cutting machines. they tout that they do a better job as they compensate for total run out of the whole assembly. seems to be very important for FWD cars especially Hondas.

So are these machines really the best for machining rotors? do they prevent or lessen the chance of pulsatiing pedal and wheel shake?

Re: is on car rotor cutting the best method? [Re: WhyMe] #5295561 12/16/19 12:43 AM
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The Critic Offline
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For most OEM's, machining a rotor on-car is the only method that is allowed for any warranty claims.

It is possible to match the results of an on-car lathe if you use a bench lathe that is in great condition (with a knowledgeable operator), but these are far and few.


2011 Toyota Prius 1.8L - 202K - Valvoline Premium Blue Restore 10W-30
2007 Honda Accord 2.4L - 143K - Valvoline Premium Blue Restore 10W-30
Re: is on car rotor cutting the best method? [Re: WhyMe] #5295578 12/16/19 01:39 AM
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Mainia Offline
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Up in the upper Midwest rust belt, rotor cutting is so 1980s, you just get new rotors. Since cutting them cost almost as much as new ones.


2018 Lowered Hyundai Kona AWD 1.6T
2014 Toyota Rav4 AWD
2005 Honda Civic
Re: is on car rotor cutting the best method? [Re: WhyMe] #5295604 12/16/19 03:16 AM
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New rotors. Turning them isn't worth the hassle.

Re: is on car rotor cutting the best method? [Re: GMBoy] #5295606 12/16/19 03:49 AM
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4WD Offline
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Originally Posted by GMBoy
New rotors. Turning them isn't worth the hassle.


And in many cases you can upgrade to more corrosion resistant discs

Re: is on car rotor cutting the best method? [Re: WhyMe] #5295635 12/16/19 05:56 AM
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Sayjac Offline
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I've had rotors turned off the vehicle on Accord and Civic several times, never an issue. I do prefer using a shop that finishes with a non directional finish or post lathe surfacing over a directional finish. I had it done for brake pulsation and it did work. ymmv

That said, I suppose if one is willing to pay the cost difference for having an on the car turning done, have at it. I'd buy new rotors before I'd do that.

Re: is on car rotor cutting the best method? [Re: WhyMe] #5295654 12/16/19 06:38 AM
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Gebo Offline
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I have never had good luck turning my rotors. Of course, I probably made bad choices in where I took my rotors to be turned.

I only buy new OEM rotors and OEM pads now.


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Re: is on car rotor cutting the best method? [Re: WhyMe] #5295668 12/16/19 06:48 AM
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Donald Online Content
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Many years ago some 4WD vehicles (Ford Ranger) had the rotor integrated into the hub and you had to take apart the entire hub to remove the rotor. In that case on-vehicle rotor machines were used. Today people just get new rotors.


2015 Ford F-250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: is on car rotor cutting the best method? [Re: Mainia] #5295685 12/16/19 07:04 AM
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atikovi Offline
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Originally Posted by Mainia
Since cutting them cost almost as much as new ones.


Not when a new replacement rotor is $500-$1,000.

Re: is on car rotor cutting the best method? [Re: WhyMe] #5295696 12/16/19 07:18 AM
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sdowney717 Offline
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I have only ever bought a set of rotors and that was for ones that were rusted on. I had to cut and split them off with a chisel. I have even taken rotors off and ground them by hand on my concrete driveway to remove a edge ridge. None of the rotors out of some 10 cars have ever caused brake problems. I buy lifetime brake pads and DIY.
They also don't shake, but I do have one Ford Contour that does shake a tiny bit, but they are not warped, they have some hard spots on the metal surface.

I use rotors others would cringe at as they are not perfect and smooth and swear they must be ground and the car stops fine with new brake pads. Take that car into a mechanics shop and they will tell you new rotors or turn them. the car business will kill you with money costs unless you know what your about, and I have wrenched for 40 years and used to be a mechanic at a Chevy dealer, yeah we would make the customer buy all sorts of new stuff even if the original parts were still ok.

Re: is on car rotor cutting the best method? [Re: WhyMe] #5295699 12/16/19 07:19 AM
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Cujet Offline
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It's good to know that if a rotor warps when hot, it's going to warp when hot after it's been turned.

One thought is that the recycled metals are distributed unevenly in the disk. Another is uneven cooling, the metals in one location were "tempered" by a red-hot stop, then keeping the pads clamped on that location while the rest of the rotor slowly cools.

Regardless of why it happens, "IF" you experience heat related warping, replace the rotor.


People who count on their fingers should maintain a discreet silence.
Re: is on car rotor cutting the best method? [Re: Cujet] #5295717 12/16/19 07:39 AM
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sdowney717 Offline
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Originally Posted by Cujet
It's good to know that if a rotor warps when hot, it's going to warp when hot after it's been turned.

One thought is that the recycled metals are distributed unevenly in the disk. Another is uneven cooling, the metals in one location were "tempered" by a red-hot stop, then keeping the pads clamped on that location while the rest of the rotor slowly cools.

Regardless of why it happens, "IF" you experience heat related warping, replace the rotor.

https://www.onallcylinders.com/2017/05/19/6-biggest-brake-rotor-myths-debunked/

Rotors do not warp. I am a mechanic. It is a myth. I did turn one badly once and since it was not true it pulsated and had to get re-turned.

https://www.brakeandfrontend.com/warped-rotors-myth/

https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3043065/1
https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3895543/all/Brakes_Rotors_DON'T_WARP__-__A

Re: is on car rotor cutting the best method? [Re: WhyMe] #5295723 12/16/19 07:50 AM
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ragtoplvr Online Content
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Replace rotors. Here, I mask them off and paint them. Not much snow here in southern joplin

Rod

Re: is on car rotor cutting the best method? [Re: WhyMe] #5295748 12/16/19 08:19 AM
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I have not had rotors turned since my 1988 Dodge Daytona.


Mike
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Re: is on car rotor cutting the best method? [Re: sdowney717] #5295916 12/16/19 11:40 AM
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UncleDave Offline
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Originally Posted by sdowney717
Originally Posted by Cujet
It's good to know that if a rotor warps when hot, it's going to warp when hot after it's been turned.

One thought is that the recycled metals are distributed unevenly in the disk. Another is uneven cooling, the metals in one location were "tempered" by a red-hot stop, then keeping the pads clamped on that location while the rest of the rotor slowly cools.

Regardless of why it happens, "IF" you experience heat related warping, replace the rotor.

https://www.onallcylinders.com/2017/05/19/6-biggest-brake-rotor-myths-debunked/

Rotors do not warp. I am a mechanic. It is a myth. I did turn one badly once and since it was not true it pulsated and had to get re-turned.

https://www.brakeandfrontend.com/warped-rotors-myth/

https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3043065/1
https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3895543/all/Brakes_Rotors_DON'T_WARP__-__A


Thats what Ive found

Rotors dont really warp, pad material imprints on them and causes the pedal to pulse and the wheel to shake.

The phenomena is called non-uniform pad imprinting.

Ive seen a hundred rotors on a lathe and have yet to see one thats warped.

UD


Uncle Dave
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