XJ ( X351 ) 2009 - 2019

Rotor Replacement Necessary?

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Old Nov 13, 2021 | 01:10 AM
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Freddy J's Avatar
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Default Rotor Replacement Necessary?

Gentlemen, I'm told that the rotors on our X351s cannot be turned i.e. resurfaced because they're to thin. Is that true? I have a slightly warped rotor on the front that drives me crazy when I lightly press the brake pedal. The pads are only 1/2 gone. Can I get the original untouched rotors resurfaced or do I have to buy new rotors? And then a front brake job while I'm at it, of course.
 
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Old Nov 13, 2021 | 03:15 AM
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Originally Posted by Freddy J
Gentlemen, I'm told that the rotors on our X351s cannot be turned i.e. resurfaced because they're to thin. Is that true? I have a slightly warped rotor on the front that drives me crazy when I lightly press the brake pedal. The pads are only 1/2 gone. Can I get the original untouched rotors resurfaced or do I have to buy new rotors? And then a front brake job while I'm at it, of course.
Are you sure the disc(rotor) is warped? There are other causes of brake judder and warped discs is low down on that list.
I'm not aware that the brake discs for the X351 are any different from any other brake discs so can't think why you couldn't get them skimmed. But in the UK, even Brembo discs are relatively cheap so makes sense to fit new ones.
 
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Old Nov 13, 2021 | 04:00 AM
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A lot depends on how worn your discs are. Skimming in a clever machine to restore trueness is OK provided it doesn't take the disc below the minimum thickness. All discs have a defined minimum thickness and this is especially important with vented discs.
 
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Old Nov 13, 2021 | 04:10 AM
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It depends to a degree on which brakes you have.
The official JLR brake rotor minimum thickness specs are ridiculously conservative, a whopping 2 mm less than new, see the attached jpg.
This is from the 2010/2011 XFR (X250) Workshop Manual but the same specs apply to the X351.
I suspect you have the 355 mm front brakes and the 326 mm rear brakes, in which case the minimum specified thickness for the front brakes is 30 mm and for the rears it is 24 mm.
Grab a Vernier caliper and measure the thickness yourself, easy enough to do.
Then allow around .25 mm for turning/resurfacing/skimming.
If the rotors will still be in spec after skimming then there is absolutely no reason why they can't be skimmed.
I had the rotors skimmed on my old 2010 XFS (same 355mm and 326 mm brakes) shortly after I bought it in 2013, in preparation for fitting new pads, and I had zero problems.


 
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Old Nov 13, 2021 | 01:13 PM
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What is often thought of as warped rotors are actually deposits from the pads fused to the rotor. The Internet has sites that discuss the symptoms and cures. Maybe try this before proceeding with machining or replacing.
If you find that replacement is necessary, I can recommend the (Chinese) Carquest painted rotor, p/n YH200535P at $113 w/free shipping, assuming you drive moderately. The hat and fins are painted a heat-resistant grey. I've had mine for a year, and they still look great. The premium Advance Auto Parts pads completed my job and I have no complaints.
In addition to pads and rotors, get replacement ABS sensors (LF and RR). They are inexpensive and often cannot be reused.
 
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Old Nov 13, 2021 | 01:27 PM
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Originally Posted by Baltobernie
What is often thought of as warped rotors are actually deposits from the pads fused to the rotor. The Internet has sites that discuss the symptoms and cures. Maybe try this before proceeding with machining or replacing.
If you find that replacement is necessary, I can recommend the (Chinese) Carquest painted rotor, p/n YH200535P at $113 w/free shipping, assuming you drive moderately. The hat and fins are painted a heat-resistant grey. I've had mine for a year, and they still look great. The premium Advance Auto Parts pads completed my job and I have no complaints.
In addition to pads and rotors, get replacement ABS sensors (LF and RR). They are inexpensive and often cannot be reused.
I think you mean the brake pad wear sensors. You shouldn't have to touch the ABS sensors (which are on all four wheel hubs).
 
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Old Nov 13, 2021 | 02:06 PM
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Correct. My bad.
 
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Old Nov 16, 2021 | 10:55 PM
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Thanks for the comments, guys. Appreciate the spec sheet. I'll see about pad deposits. I've had warped rotors before and know what it feels like in the steering wheel. I'll look into finding a shop that will skim the front rotors. My shop only replaces them.
 
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Old Nov 17, 2021 | 06:51 AM
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I personally don't believe that discs (rotors) warp. Not with everyday road use and certainly not the ventilated ones. Skimming may well cure the brake judder but only because the surfaces are being cleaned up of the burnt-in brake material.
As far as possible, don't sit stationary with your foot pressed on the brake pedal, especially if you've just had to do some heavy braking (coming down a steep hill for example). That's a sure way to burn the pad material into the disc surface. Try to learn to use the parking brake when you can.
 
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Old Nov 17, 2021 | 10:00 AM
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Yes replace the wear sensors if you get the dash indication. If you change the pads early you can reuse the factory wear sensors. You can also connect the two wires together and bypass the wears sensors permanently if you don't want to mess with them anymore.
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