Impreza WRX rotors - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Flasher · 07-05-2016, 11:32 AM

So I heard in the German FT86 forums somone suggesting to use the 2002 Impreza WRX rotors as an upgrade option. The user stated, that those rotors are proven to be "better" by experience. He mentioned Brembo 09.9077.10 which are in fact the same size than the "original" Brembo 09.A921.14.

Does anyone know what the difference between the two is and why the WRX rotors should be better?

wparsons · 07-05-2016, 11:40 AM

I don't know which year range is applicable, but the WRX rotors are the exact same part as the factory FRS/BRZ/GT86 rotors.

I would ask how they were better by experience... longer wear? There's nothing wrong with the stock rotors, I got over 100k km's on mine with lots of track use.

Flasher · 07-06-2016, 03:15 AM

Quote:

Originally Posted by wparsons

WRX rotors are the exact same part as the factory FRS/BRZ/GT86 rotors.

I'm not so sure about that - I checked the technical drawings for the FT86 rotors (Brembo P/N 09.A921.14) and I noticed that the WRX rotors (Brembo P/N 09.9077.10) have a wider gap for ventilation (7.5 mm vs 9 mm). Brembo also mentions that there are fewer ventilation fins in the WRX rotor.

Quote:

I would ask how they were better by experience... longer wear?

I don't know. I guess they tolerate more aggressive pads? Due to the wider venting gap I would also assume, that cooling is improved?

wparsons · 07-06-2016, 11:31 AM

Quote:

Originally Posted by Flasher

I'm not so sure about that - I checked the technical drawings for the FT86 rotors (Brembo P/N 09.A921.14) and I noticed that the WRX rotors (Brembo P/N 09.9077.10) have a wider gap for ventilation (7.5 mm vs 9 mm). Brembo also mentions that there are fewer ventilation fins in the WRX rotor.

Is the rotor thickness the same on both? If so, the ones with a wider gap actually have less thermal capacity due to less metal. They could end up running hotter despite having more air space.

Quote:

Originally Posted by Flasher

I don't know. I guess they tolerate more aggressive pads? Due to the wider venting gap I would also assume, that cooling is improved?

Per above, if the rotor isn't thicker but the inner air space is increased you've removed thermal mass and in the process given the rotor less material to wear off before it becomes too thin. 1.5mm isn't a huge amount, but it still less metal to wear and/or absorb heat.

Which of the rotors is a newer revision? I would bet the WRX parts are old, and have been replaced across the board by the new FRS part, even for WRX fitment.

Flasher · 07-06-2016, 12:50 PM

Quote:

Originally Posted by wparsons

Is the rotor thickness the same on both? If so, the ones with a wider gap actually have less thermal capacity due to less metal. They could end up running hotter despite having more air space.

Per above, if the rotor isn't thicker but the inner air space is increased you've removed thermal mass and in the process given the rotor less material to wear off before it becomes too thin. 1.5mm isn't a huge amount, but it still less metal to wear and/or absorb heat.

Which of the rotors is a newer revision? I would bet the WRX parts are old, and have been replaced across the board by the new FRS part, even for WRX fitment.

So this is the WRX part

And that's the FT86 part

Dimensionwise the parts look identical except for the gap in the middle. As for the age of the parts - the WRX technical drawing has a more recent date (2014 vs. 2013). Dunno if that is also applicable for the design, or just the drawing.

cdrazic93 · 07-06-2016, 04:12 PM

So as wparsons was mentioning, the diagram seems to show the FRS rotors actually having more rotor material to be used than the WRX rotors. The 1.5mm difference is given to the rotor side of the equation, giving the FRS discs a slight thermal edge. Ofcourse this is 2002 WRX brakes.

Flasher · 07-08-2016, 09:39 AM

OK I know that bigger rotors are better performing due to the bigger surface, higher heat capacity, and better cooling but does that also apply for rotors with only a weight difference?

I assume that you can put more heat in heavier discs, while the lighter rotors have an advantage in cooling?

ZionsWrath · 07-08-2016, 10:02 AM

If they changed it to add more material there must have been a reason. It would have been cheaper to use the existing old part.

Just my opinion.

07-05-2016, 11:32 AM	#1
Flasher Smartass Join Date: Jan 2013 Drives: Toyota GT86 & Impreza STi Location: Germany Posts: 105 Thanks: 60 Thanked 17 Times in 10 Posts Mentioned: 1 Post(s)	Impreza WRX rotors So I heard in the German FT86 forums somone suggesting to use the 2002 Impreza WRX rotors as an upgrade option. The user stated, that those rotors are proven to be "better" by experience. He mentioned Brembo 09.9077.10 which are in fact the same size than the "original" Brembo 09.A921.14. Does anyone know what the difference between the two is and why the WRX rotors should be better? __________________ Toyota GT86, Leather, JBL-Sound, Aero-Kit, inferno orange MODS \|O.Z Leggera 18 x 8,5\|Front:Tarox B32\|Rear:OEM+EBC GreenStuff\|Braided Lines\|Milltek CAT-Back & Overpipe\|Motiv Concepts catted Frontpipe\| AVO Turbo\|AVO breather tank\|Mishimoto Oilcooler\|Exedy Stage 1 Clutch\|BeatSonic Sharkfin\|TRD Ducktail\|TRD Aero cover\|Valenti blinker

07-06-2016, 04:12 PM	#6
cdrazic93 Junior Join Date: Aug 2013 Drives: a car Location: Probably at school Posts: 4,341 Thanks: 3,184 Thanked 2,512 Times in 1,502 Posts Mentioned: 20 Post(s)	So as wparsons was mentioning, the diagram seems to show the FRS rotors actually having more rotor material to be used than the WRX rotors. The 1.5mm difference is given to the rotor side of the equation, giving the FRS discs a slight thermal edge. Ofcourse this is 2002 WRX brakes. __________________ "Ah! What music! They could have never imagined, those pioneers who invented the automobile, that it would posses us like this, our imaginations, our dreams. Men love women, but even more than that, men love CARS!"-Lord Hesketh

07-08-2016, 09:39 AM	#7
Flasher Smartass Join Date: Jan 2013 Drives: Toyota GT86 & Impreza STi Location: Germany Posts: 105 Thanks: 60 Thanked 17 Times in 10 Posts Mentioned: 1 Post(s)	OK I know that bigger rotors are better performing due to the bigger surface, higher heat capacity, and better cooling but does that also apply for rotors with only a weight difference? I assume that you can put more heat in heavier discs, while the lighter rotors have an advantage in cooling? __________________ Toyota GT86, Leather, JBL-Sound, Aero-Kit, inferno orange MODS \|O.Z Leggera 18 x 8,5\|Front:Tarox B32\|Rear:OEM+EBC GreenStuff\|Braided Lines\|Milltek CAT-Back & Overpipe\|Motiv Concepts catted Frontpipe\| AVO Turbo\|AVO breather tank\|Mishimoto Oilcooler\|Exedy Stage 1 Clutch\|BeatSonic Sharkfin\|TRD Ducktail\|TRD Aero cover\|Valenti blinker

07-08-2016, 10:02 AM	#8
ZionsWrath Thanks Join Date: Apr 2013 Drives: BRZ Location: NY Posts: 4,163 Thanks: 5,989 Thanked 3,100 Times in 1,498 Posts Mentioned: 38 Post(s)	If they changed it to add more material there must have been a reason. It would have been cheaper to use the existing old part. Just my opinion. __________________

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