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      12-22-2019, 07:16 PM   #1
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Dimpled & Slotted Brembo Rotors

Just finished installing new front rotors along with Hawk HPS 5.0 pads. This is my first time using non-blank rotors, and during the bedding in process, I noticed a slight rhythmic thumping sound during hard braking. ("Dook-dook-dook-dook-dook-..." ) Is this normal due to the dimples & slots? Or did I potentially screw something up during the install? It wasn't really loud, but noticeable.

Braking performance seemed to be fine...better than the oem pads and rotors that were replaced I think, though it's hard to tell without a longer test drive and some more real world braking situations.
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      12-22-2019, 07:19 PM   #2
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Check for uneven bedding. I have drilled and have no such problems.
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      01-16-2020, 09:39 AM   #3
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Great looking rotors. Where did you get them?
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      01-16-2020, 10:55 AM   #4
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Quote:
Originally Posted by Randy Johnson View Post
Great looking rotors. Where did you get them?
Thanks! I'm digging them.

Amazon

Brembo 09.C398.13 Front Disc Brake Rotor
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      01-17-2020, 02:54 PM   #5
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Test drive

Hi jh_f30,

I'm thinking about doing the very same brake upgrade but only if there is a noticeable performance improvement against OEM.

Could you report back on this thread after you have had a chance to test them out properly and let us know your thoughts on performance then?

That would be a great help, thanks in advance.
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      01-17-2020, 02:58 PM   #6
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Was it the sound of ABS kicking in? My disks make some noise but only noticeable when driving next to a barrier.
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      01-17-2020, 03:43 PM   #7
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Quote:
Originally Posted by longreach View Post
Hi jh_f30,

I'm thinking about doing the very same brake upgrade but only if there is a noticeable performance improvement against OEM.

Could you report back on this thread after you have had a chance to test them out properly and let us know your thoughts on performance then?

That would be a great help, thanks in advance.
Which brake upgrade? Which car and brakes do you have now? What are you looking to do?
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      01-17-2020, 04:09 PM   #8
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Quote:
Originally Posted by longreach View Post
Hi jh_f30,

I'm thinking about doing the very same brake upgrade but only if there is a noticeable performance improvement against OEM.

Could you report back on this thread after you have had a chance to test them out properly and let us know your thoughts on performance then?

That would be a great help, thanks in advance.
Braking performance seems to have improved with the new rotors and the Hawk pads. Though, since I changed them both at the same time, it's hard to say if the performance is attributable to one or the other (or both). From what I've read, braking performance is primarily a function of the pad compounds, the drilled/dimpled and slotted rotors serve different functions than strictly stopping distance.

One thing to note though, the Hawk pads do seem to dust a bit more than the stock Brembo pads I had previously. Noticeably dirtier front wheels during my last wash.
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      01-17-2020, 04:11 PM   #9
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Quote:
Originally Posted by andino View Post
Was it the sound of ABS kicking in? My disks make some noise but only noticeable when driving next to a barrier.
Yeah, same for me. Can't tell unless I'm driving next to something. I noticed a similar clicking-type noise from FaRKle!'s car during our last meetup so I'm thinking it's pretty normal for this style of rotor. I'm not too worried about it anymore.
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      01-17-2020, 04:42 PM   #10
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Quote:
Originally Posted by jh_f30 View Post
Yeah, same for me. Can't tell unless I'm driving next to something. I noticed a similar clicking-type noise from FaRKle!'s car during our last meetup so I'm thinking it's pretty normal for this style of rotor. I'm not too worried about it anymore.
Yeah Farkie's car is a lot quieter than mine but I think mine also makes sounds on braking. Only really hear it when I'm at the track though since my car makes a lot of other noises.
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      01-17-2020, 07:17 PM   #11
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This is a normal noise. Good discussion to read:

https://f30.bimmerpost.com/forums/sh...d.php?t=826559

In short - the air gets trapped in dimples and wants to emerge. As the rotors get hotter, the air also expands quicker and pushes back on the brake pad as the pad floats over the dimples.

I am not a big fan of BMW dimpled / slotted rotors. For daily driving, plain rotors work well.

AP Racing J Hook rotors are much better - the J Hook part vs dimples / slots - and of course more expensive.

https://apradical.stillen.com/brake-...k-brake-rotors
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      01-17-2020, 07:18 PM   #12
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Oh ... Yellow calipers are well matched with exterior red color.
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      01-17-2020, 08:14 PM   #13
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Quote:
Originally Posted by cfm56d7b View Post
This is a norma noise. Good discussion to read:

https://f30.bimmerpost.com/forums/sh...d.php?t=826559

In short - the air gets trapped in dimples and wants to emerge. As the rotors get hotter, the air also expands quicker and pushes back on the brake pad as the pad floats over the dimples.

I am not a big fan of BMW dimpled / slotted rotors. For daily driving, plain rotors work well.

AP Racing J Hook rotors are much better - the J Hook part vs dimples / slots - and of course more expensive.

https://apradical.stillen.com/brake-...k-brake-rotors
Those rotors do look good. Cost was a big factor in my decision. I don't track and its my daily driver. I needed new rotors anyways and was interested largely in the aesthetic of drilled/dimpled and slotted over blank rotors. The price and construction of these and the fact they're Brembos pushed me over the edge.
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      01-17-2020, 08:17 PM   #14
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Quote:
Originally Posted by cfm56d7b View Post
Oh ... Yellow calipers are well matched with exterior red color.
Thanks! Techinically, they're "gold". Specifically didn't go with yellow because of the association of that combo on Ferraris, and a Ferrari my car is not.
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      01-17-2020, 10:30 PM   #15
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Quote:
Originally Posted by BMWILUVU View Post
Check for uneven bedding. I have drilled and have no such problems.
Drilled rotors work much better for street performance. Great bite and they shed water to maintain braking in the rain. Slotted rotors are a great design for very hot track conditions but noise is a common complaint when used as a daily driver.
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      01-17-2020, 11:03 PM   #16
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Quote:
Originally Posted by jh_f30 View Post
Quote:
Originally Posted by cfm56d7b View Post
Oh ... Yellow calipers are well matched with exterior red color.
Thanks! Techinically, they're "gold". Specifically didn't go with yellow because of the association of that combo on Ferraris, and a Ferrari my car is not.
Gold it is!
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      01-19-2020, 09:20 PM   #17
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Quote:
Originally Posted by johnung View Post
Drilled rotors work much better for street performance. Great bite and they shed water to maintain braking in the rain. Slotted rotors are a great design for very hot track conditions but noise is a common complaint when used as a daily driver.
I use solid rotors for track. The drilled is for lookin' pretty on the street.
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      01-20-2020, 06:50 AM   #18
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Originally Posted by BMWILUVU View Post
Quote:
Originally Posted by johnung View Post
Drilled rotors work much better for street performance. Great bite and they shed water to maintain braking in the rain. Slotted rotors are a great design for very hot track conditions but noise is a common complaint when used as a daily driver.
I use solid rotors for track. The drilled is for lookin' pretty on the street.
You're right, besides being functional on the street, drilled rotors definitely look pretty. Guess that's why often see them on Porsche, McLaren, Mercedes, etc.
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      01-20-2020, 08:19 AM   #19
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For whatever it's worth, I think F1 and LMP-series cars use solid rotors. GTE-class race cars I think use slotted. NASCAR drivers don't really use their brakes during a race, so that's moot.
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      02-13-2020, 06:02 PM   #20
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Yo! Long time no see bro! Would you recommend the Hawks HPS 5.0? I just wanted a daily brake pad that is good for some spirited driving in the back roads when I do decide to push the car a bit.
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      02-13-2020, 06:09 PM   #21
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From what I remember, the pads area more of an integral piece when it comes to stopping distance and the slotted/drilled rotors allow the brakes to work longer as the passage ways allow for more air to cool the rotors. I read this many years ago though.. not sure if the science behind that has been proven/disproven as you said LMP and F1 uses solid rotors.. who knows. haha
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      02-13-2020, 06:57 PM   #22
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Quote:
Originally Posted by Calvin36 View Post
From what I remember, the pads area more of an integral piece when it comes to stopping distance and the slotted/drilled rotors allow the brakes to work longer as the passage ways allow for more air to cool the rotors. I read this many years ago though.. not sure if the science behind that has been proven/disproven as you said LMP and F1 uses solid rotors.. who knows. haha
Hey Calvin! Definitely long time! I do really like the Hawks and I'll probably continue using them moving forward. The only caveat is that for me, they seem to dust a bit more than the oem pads I had before. Not sure if it's strictly the pad compound or the dimpled/slotted rotors that I fitted at the same time though; possibly a combination of both.
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