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Opinion on these brake rotors

Hey everybody, I'm looking for an opinion on these brake rotors. They are for sale on Ebay and are probably made in China. Yea, I know... Chinese Junk! But I have bought similar rotors for my Chevy Tahoe in the past and they were bit bit as good as the originals. Hopefully somebody here has tried them and knows the pros and cons.
Here is the link:
https://www.ebay.com/itm/Fit-1990-Porsche-944-Front-Rear-PowerSport-Drill-Slot-Brake-Rotors/272359808782?fits=Year%3A1990%7CSubmodel%3AS2%7CMa ke%3APorsche&hash=item3f69e8df0e:g:-~kAAOSwGXpa2VAD:rk:19f:0
Old 02-03-2019, 11:13 AM
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Doesn't matter where it's made. Slotted and drilled rotors are bad design. Get something solid and you'll be better off.
Old 02-05-2019, 02:13 PM
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+1 to what Danno said

I'm attaching a link to our brake section. Some Meyle brakes would work well and total cost should be close to your link's price.

https://www.pelicanparts.com/catalog/SuperCat/1030/POR_1030_BRKPAD_pg4.htm#item10
Old 02-05-2019, 03:05 PM
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Agree that slotted and drilled stuff is a bad idea for a daily driver or a street driven machine. The stock Porshe 944 brakes kicked ass and were carefully tested when hot, when cold, on various surfaces, at various outside temps, at full load, when empty, etc, etc. Exhaustively tested. Slapping something random on there walks away from the development of the world's preeminent sports car design team. Think random will be better? Think again - carefully.
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Old 02-05-2019, 10:11 PM
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so what is 'bad' about slotted?
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Old 02-06-2019, 05:33 AM
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Quote:
Originally Posted by 911tracker85 View Post
so what is 'bad' about slotted?
While I greatly appreciate everybody's opinion, I also am curious what is bad about slotted and drilled. I thought that cooler and lighter is better but maybe not. If this is true, it will be cheaper to go solid.
Old 02-06-2019, 07:45 AM
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Quote:
Originally Posted by 911tracker85 View Post
so what is 'bad' about slotted?
Quote:
Originally Posted by Mike VS View Post
While I greatly appreciate everybody's opinion, I also am curious what is bad about slotted and drilled. I thought that cooler and lighter is better but maybe not. If this is true, it will be cheaper to go solid.
The drilled ones crack and the slotted ones warp. Ask anyone who’s had these cars on the track and they’ll tell you solid are best. I made the mistake years ago, thought I knew best and against advise fitted drilled rotors and they lasted exactly 3 DE’s before they showed cracks between the holes, totally unacceptable and they weren’t a cheap brand either, Zimmerman iirc. I’ve heard numerous reports of the slotted ones warping and causing brake “judder” very quickly.
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Old 02-06-2019, 09:15 AM
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You definitely don't want drilled rotors ... sure they look cool on the street , but that's about it !
Although i've have good success with the Sebro slotted rotors which i have on my 89 911 with 996TT brakes.
They replaced the OEM Zimmerman drilled units which didn't last very long when i was heavy into DE's with my car at the time.
I use the solid Sebro discs with Hawk Blue pads on my race car and never had an issue !
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Old 02-06-2019, 12:22 PM
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For your consideration...

Research published in the last year concludes:

...in slotted disc the redzones occur at the the edge of the rotor disc which is due to frictional force by the brake caliper. Since there are no drill holes in this type of design the convection of heat is less and hence the temperature is max compared to slotted and drilled disc brake. The maximum temperature for this disc is ~948 degrees C. in using stainless steel as material and for cast iron it is 630.18 degrees C.

Comparing the different results obtained from the analysis, it is concluded that Cast Iron is the best material for both slotted disc, because the thermal temperature and thermal stresses obtained for this material is lesser than compared to stainless steel material.
  • CI disc showed 33% reduction in temperature
  • Deformation was less in CI by 75% compared to SS
  • Slotted and drilled dissipates more heat.

Source: https://inpressco.com/wp-content/uploads/2018/01/Paper1356-60.pdf

Now for the visual learners among us:



Source: https://www.researchgate.net/publication/222532095_Wear_resistance_of_cast_irons_used_in_br ake_disc_rotors

You can also find a good explanation of the differences here: https://www.frictionmaster.com/blog/drilled-vs-slotted-disc-brake-rotors/

Given the relatively low demands our cars put on their brakes any and all options should be fine. Even in the 944 Cup series there is no demand for replacing the factory brakes.

Hope this helps.
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Last edited by curtisr; 02-06-2019 at 02:56 PM..
Old 02-06-2019, 02:50 PM
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I'm a believer now... Thanks everybody, solid disc it is.
Old 02-06-2019, 06:35 PM
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Time to find famous Altima Brake Thread...
Old 02-07-2019, 07:21 AM
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On other note, not sure if available for 944, genuine Porsche rotors with holes are not drilled. The holes are cast in place. This preserves continuous grain-boundaries that drilling would not do. However, you still end up with variable heat-gradients and stress-risers around hole. So even Porsche's own "drilled" rotors will crack. Guess which model this was from?

Old 02-07-2019, 08:30 AM
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In addition to the issues mentioned, road driving includes sand, grit, gravel and other debris not found on a track. So things can get caught in those slots and holes with predictable results. I'm a big advocate of factory parts for brakes where mismatches can cause dangerous handling with emergency evasive maneuvers.

For example. Put ceramic brake pads on the front because you've been told that's where most of the braking force is. Now come around a curve in a country road with cold brakes and a deer jumps out so you stomp the brakes. Those ceramic brakes don't grip well when cold but the factory rears will. So you feel the rear tires coming around and next thing you know you are at full lock and leaving the roadway. Later, when the wrecker is pulling what is left of your once beautiful 944 out of the ditch you will wonder why that happened.

Your brake system was carefully engineered to keep you out of trouble when the worst happens. Modify it with rotors or calipers from another vehicle because it gives you bragging rights at your own risk. I'd be willing to bet my title against your modified 944 that we could give our cars to an independent testing lab to put them through a standard OEM regimen of tests and mine would come out on top. I'd predict yours would win in a racetrack comparo where its predictable gentle curves and lots of heat buildup. But on a track there are no ice patches, deer, railroad tracks, cars pulling from side roads on a cold night, etc.

Go stock for a road car. You'll be glad you did but your friends won't think you're quite as cool as Barney with his cross drilled, slotted rotors from a Lamborghini and fluorescent green calipers from a BMW M3 and ceramic pads from some grimy factory in Outer Mongolia. And Barney will have no idea that you can outstop him by 5 feet.
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Old 02-07-2019, 09:22 AM
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One of the guys at 924board is a brake engineer for bosch (at least when I was a regular there 15 years ago) and I'll never forget a rant that he had about OEM and aftermarket drilled brake rotors. I don't think this thread is it, i'm still looking for it but you get the gist.

924Board.org :: View topic - Drilled rotors?
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Old 02-07-2019, 11:12 AM
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https://www.youtube.com/watch?v=eq9kQ_5L4m8
Old 02-07-2019, 03:01 PM
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