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Groove on New Rotors #5464888 06/28/20 01:06 PM
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bunnspecial Offline OP
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A few weeks ago, I swapped out the front factory pads and rotors on my MKZ. Amazingly enough, with ~75K, the pads still had meat on them(that's a lot of highway miles) but I had a warped rotor that was bugging me and figured that was as good a time as any.

I put NAPA gold ceramic pad and gold rotors on. I've put about 1500 miles on it since then-two ~500 mile round trips of mostly interstate, and a couple hundred around town driving.

Yesterday, in a quick once over, I saw noticeable grooves in both rotors that are deep enough that I can feel them with my finger. As can be seen, these rotors otherwise don't have much wear, with the radial machining still visible.

I'm really particular about cleanliness any time I do brake work. That includes wiping both the rotors and the pads with brake cleaner before and after application, as well as cleaning any part I remove(regreasing as appropriate) and anything around the brakes. I use the good stuff(chlorinated CRC) to both get things as clean as possible and avoid leaving residue.

Any idea what could cause this? Do I need to pull these back down and redo the job with fresh materials, or possibly just give the pad faces a quick sand and clean and hope it will smooth out? Or, alternatively, should I just let it be?


IMG_1294.jpg
Last edited by bunnspecial; 06/28/20 01:07 PM.

2010 Lincoln MKZ-Mobil 1 5W-30
1970 MG MGB Roadster-Valvoline VR-1 20W-50
1974 Austin Marina GT VR-1 20W-50
Re: Groove on New Rotors [Re: bunnspecial] #5464895 06/28/20 01:13 PM
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I noticed the same grooves when I did the brakes on my `06 Odyssey (Wagner Thermoquiet pads and Centric Premium rotors). Although not something you want to see that soon. I think it might be the nature of running ceramic pads and would consider it normal.

Last edited by zfasts03; 06/28/20 01:15 PM.

- 03 Corvette Z06
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Re: Groove on New Rotors [Re: bunnspecial] #5464898 06/28/20 01:15 PM
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hallstevenson Offline
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Are you referring to the difference in color on the inner 2/3rds of the rotor ? I can't make out "grooves" in the picture myself but maybe it's my eyes.

Is this only on one corner or more than one ? If it's just the one, I'd pull the pad and look for debris on the face of it and clean it up.

Re: Groove on New Rotors [Re: hallstevenson] #5464902 06/28/20 01:18 PM
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bunnspecial Offline OP
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Originally Posted by hallstevenson
Are you referring to the difference in color on the inner 2/3rds of the rotor ? I can't make out "grooves" in the picture myself but maybe it's my eyes.

Is this only on one corner or more than one ? If it's just the one, I'd pull the pad and look for debris on the face of it and clean it up.


There are a few "lighter" areas-one a bit in from the perimeter and the others closer to the center. I see similar grooves on both sides. They're not deep, but as I said I can feel them.


2010 Lincoln MKZ-Mobil 1 5W-30
1970 MG MGB Roadster-Valvoline VR-1 20W-50
1974 Austin Marina GT VR-1 20W-50
Re: Groove on New Rotors [Re: bunnspecial] #5464910 06/28/20 01:26 PM
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Trav Offline
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This is all normal, the new pads have different materials in them at different angles in the paste used to form the friction pads. they will bed in and smooth out, leave it be.
Think of it as metal flake in paint some the flakes do not lay flat, they are all over the place.


ASE L1, Master. Deutsch Meisterbrief.
Re: Groove on New Rotors [Re: bunnspecial] #5464911 06/28/20 01:26 PM
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eljefino Online Content
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Let it go. If anything it's slightly more surface area.

Re: Groove on New Rotors [Re: Trav] #5464913 06/28/20 01:31 PM
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hallstevenson Offline
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Originally Posted by Trav
they will bed in and smooth out, leave it be.

Replying to your post for context but 'bunnspecial', did you do any "brake bedding" after installation ? Some feel it's not necessary - just drive relatively normal for a while - while others insist on doing it.

Re: Groove on New Rotors [Re: bunnspecial] #5464915 06/28/20 01:35 PM
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Chris142 Offline
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Normal. No reason at all to take it apart.


02 Wrangler Napa high milage 10w40
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Re: Groove on New Rotors [Re: hallstevenson] #5464922 06/28/20 01:42 PM
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bunnspecial Offline OP
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Originally Posted by hallstevenson
Originally Posted by Trav
they will bed in and smooth out, leave it be.

Replying to your post for context but 'bunnspecial', did you do any "brake bedding" after installation ? Some feel it's not necessary - just drive relatively normal for a while - while others insist on doing it.


On my initial test drive, after making sure they were otherwise working okay, I did a few 20-10 stops, a few 40-10, and then when I found some open road did 60-10 a few times and drove to let them cool down without coming to a complete stop.

In any case, thanks for all the replies. I don't remember seeing this before in the dozen or so brake jobs I've done myself, but if you experience folks say it's normal I'll let it be.

Last edited by bunnspecial; 06/28/20 01:43 PM.

2010 Lincoln MKZ-Mobil 1 5W-30
1970 MG MGB Roadster-Valvoline VR-1 20W-50
1974 Austin Marina GT VR-1 20W-50
Re: Groove on New Rotors [Re: bunnspecial] #5464985 06/28/20 03:36 PM
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Trav Offline
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Probably no need to "bed" those in, you may induce brake squeal with some non performance pads eg Bendix CT-3, made in USA ones didn't care if they were bed in or not but the made in China versions would squeal like a pig with its foot caught. Nothing you can do not except leave it it alone, nothing bad happened.


ASE L1, Master. Deutsch Meisterbrief.
Re: Groove on New Rotors [Re: bunnspecial] #5465077 06/28/20 06:31 PM
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bunnspecial Offline OP
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Fortunately no squeal, so I'm guessing I didn't harm it any with the bed-in.

I tossed the box so can't give country of origin. All I really remember is they were NAPA golds.

Funny enough, I'd had them sitting around 2 years or so. Somewhere around 40K on the car, I put new tires on it, and on fresh tires I started noticing a slight brake shudder. Since my grandfather bough this car new and it live its first ~10K or so driving in the NC mountains, I figured the brakes were probably due for a change and picked these up without bothering to check. When I pulled the wheels and saw over 50% of the pads, I buttoned it all back up and said "I'll live with the shudder-I can't toss pads that look this good." They sat around for another 35K miles before my furlough from work had me looking for projects and I said "These are down to about 10%-I should probably change them."


2010 Lincoln MKZ-Mobil 1 5W-30
1970 MG MGB Roadster-Valvoline VR-1 20W-50
1974 Austin Marina GT VR-1 20W-50
Re: Groove on New Rotors [Re: bunnspecial] #5465095 06/28/20 06:56 PM
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sloinker Offline
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Buy some drilled and slotted rotors so you stop seeing the patterns in the future.


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'14 Dodge Grand Caravan 3.6 Valvoline 5W20 Semi Synthetic
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Re: Groove on New Rotors [Re: bunnspecial] #5465144 06/28/20 07:55 PM
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spk2000 Offline
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Looks normal. I would leave it


96 Grand Marquis 203,000 mi
01 Sable LS Wagon 163,000 mi
02 Montero 191,000 mi
03 Sable LS Sedan 73,000 mi
Re: Groove on New Rotors [Re: bunnspecial] #5465235 06/28/20 09:49 PM
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Avery4 Offline
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Looks fine to me smile

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