RDA slotted and drilled disks

by **gtsti7** » Sun Feb 10, 2013 5:28 pm

I know rda are not as good as dba, but I'm looking at getting front and back rda drilled and slotted for my 07 lib sti. Is there still a high chance of if cracking if I don't take it to the track? Thanks

by **dawesy** » Sun Feb 10, 2013 6:50 pm

From what a guy was saying at a brake and suspension place that rda have changed their manufacturing process to similar to dba weather the quality is as good duno but apparently theyre on the improvement

by **HyRax** » Sun Feb 10, 2013 8:30 pm

I've cracked cross-drilled rotors on the street myself - doing a downhill run of Macquarie Pass (NSW). Never again will I buy cross-drilled. It's pretty factor only that cannot handle any remotely serious driving.

And before you ask, they were not cheap rotors either. They were DBA's (their old gold and silver street series, which is mostly just bling-spec anyway). It doesn't matter the brand anyway - cross-drilled promotes micro cracks which very quickly turn into major cracks if the rotor cools unevenly. They are simply not worth it if you like to do the occasional spirited run through a twisty mountain road, especially if you're on a steep downhill run.

by **ferret89** » Sun Feb 10, 2013 8:41 pm

HyRax wrote:I've cracked cross-drilled rotors on the street myself - doing a downhill run of Macquarie Pass (NSW). Never again will I buy cross-drilled. It's pretty factor only that cannot handle any remotely serious driving.

And before you ask, they were not cheap rotors either. They were DBA's (their old gold and silver street series, which is mostly just bling-spec anyway). It doesn't matter the brand anyway - cross-drilled promotes micro cracks which very quickly turn into major cracks if the rotor cools unevenly. They are simply not worth it if you like to do the occasional spirited run through a twisty mountain road, especially if you're on a steep downhill run.

^ this

Thats pretty much what I heard, drilled rotors leads to cracked rotors. Slotted are the way to go

by **gtsti7** » Sun Feb 10, 2013 9:34 pm

Thanks guys, I thought it was an exaggeration when I heard from others. Can you please explain though why AMG BMW And other good brands put drilled in their sports cars then? Are their quality much better than dba? I am set on only slotted now, but I'm just curious why good car brands use drilled on performance cars if they crack?

by **xyz** » Sun Feb 10, 2013 10:02 pm

^^ I've always wondered the same

by **J0HNATH0N** » Sun Feb 10, 2013 10:43 pm

if you are going to go slotted then atleast make sure you go the 4000 series for DBA or the equivalent in other brands. I was told by DBA that they are heat treated or something and will allow more of a hammering....

by **HyRax** » Sun Feb 10, 2013 11:15 pm

gtsti7 wrote:but I'm just curious why good car brands use drilled on performance cars if they crack?

Because those rotors are usually made of carbon not iron.

Even those running iron rotors generally have much larger rotors than a typical Subaru, sometimes with aluminium hats, so they dissipate heat far better than a smaller one-piece rotor. Less stored heat, less thermal shock, equals less micro cracks which reduces the chance of a major crack.

by **Deep Heat** » Mon Feb 11, 2013 2:12 am

dawesy wrote:From what a guy was saying at a brake and suspension place that rda have changed their manufacturing process to similar to dba weather the quality is as good duno but apparently theyre on the improvement

RDA rotors are very good for the money. I had a set on my liberty and a set on mum's commodore. I've got them very hot and they didn't warp or crack. One thing I noticed was that they wear faster than DBA rotors probably because the RDA have less carbon in them.

by **cruisn** » Mon Feb 11, 2013 5:14 am

The RDA's are not drilled, theyre dimpled.......ie, not drilled right through.

Im running them.......

Theyre equivalent to DBA street series rotors which also arent heat treated. Depends what sort of driving you do as to what you need.

by **HyRax** » Mon Feb 11, 2013 7:28 am

cruisn wrote:The RDA's are not drilled, theyre dimpled.......ie, not drilled right through.

<squints closer at image on screen>

Hmmm... I do believe you are right. Who on earth advertises dimpled as drilled?

In that case there's no problem. These rotors would last much longer in an abusive situation than drilled rotors would.

/thread.

by **senator** » Mon Feb 11, 2013 8:10 am

gtsti7 wrote:Thanks guys, I thought it was an exaggeration when I heard from others. Can you please explain though why AMG BMW And other good brands put drilled in their sports cars then? Are their quality much better than dba? I am set on only slotted now, but I'm just curious why good car brands use drilled on performance cars if they crack?

Thermal cracking occurs on cheaper rotors due to the veins between the rotors faces not being thin to disperse the heat.

The rotor below is Audi RS5/R8 OE rotor which is crossed drilled, but look at the how the outer rotor is mounted to the centre hub…… minimal material unlike what RDA & DBA.