Why Are Brake Calipers on the Back of Rotors
To start, Most subarus use the same brake mounting points, so you can exchange calipers between different models, especially up front, where the caliper mounting hasn't changed since the 1990 legacy. If you want WRX brakes on your L or something you pretty much just have to buy some and bolt them on. The rear brakes do get a little more complicated, however. I mention it a bit later on.
And also in this thread.
Additionally, Subaru uses two bolt patterns, 5x100, and 5x114. Conveniently, many rotors come in both patterns and it is not that hard to have them re-drilled, if, say, you had some 5x114 sti rotors and wanted to use them on an older car. Note: re-drilling 5z100 front rotors to 5x114 does not work as they will not fit over the hubs.
If your car has rear drum brakes, a disc swap is fairly more involved. I'm not entirely sure on the process but there are more details farther down.
In the rear, things get a little more tricky. There are different sized parking brakes, and different caliper mounting, and "old" vs 'new" rear uprights. Brake parts on the current cars with multi-link rear suspension do not interchange with older strut suspension parts. The 00-09 Legacy, while a multi link design, still uses the older mounting. it also appears that the tribeca, which has the new rear suspension still uses "old" rear brakes.
So, if you're wondering what brakes you have and what other brakes are out there, I've made this big list of most of the different brakes found on modern Subarus. The information came from a lot of places like the DBA catalog (click the rotor size for spec sheets provided by DBAsteve), cars101, and various threads/FAQs here and on scoobymods. This is mostly just about US model cars. Generally brakes were the same around the world but there are a few little special exceptions that are linked to later on.
Disclaimer: While I have tried to make this post as accurate as possible, there are some mid year revisions. I also can't be positive all the year ranges listed are correct, especially for pad shapes. In some cases, it is necessary to call a dealership with your VIN number or physically compare parts.
Front Brakes 242x18mm
Smallest Subaru front brakes, found on FWD non-abs Imprezas (93-96). The caliper and bracket are similar to those for early 260mm brakes with a shorter bracket and they use the same pads. These things fit under 13" wheels.
Applications:
93-96 Impreza 2WD.
260x24mm
This is the most common front rotor size before 2000. It was found on many Imprezas and Legacies and uses a single piston caliper and bracket. Somewhere around 96/97 the caliper/bracket/pad design changed. These fit under 14" wheels.
Applications:
90-99 Legacy non-turbo/-GT/-Outback
1995 Outback
93-01 Impreza AWD (non RS)
276x24mm
This uses a two piston sliding front caliper and there are three caliper/bracket designs. One for the 91-94 Legacy SS/TW, an early Legacy 2.5GT/Impreza RS bracket (~96-99), and a Later RS/GT bracket (03+). It's possible to exchange some of these calipers onto taller WRX brackets as long as the pad shapes match.
Applications:
91-94 Legacy turbo
96-01 Legacy GT
96-01 Outback
00-04 Legacy non-GT
98+ Impreza RS/TS/2.5i
98+ Forester
Some base model BRZ/FRS/86s in other markets.
292x24
294x24mm
295x25.5mm
This is the WRX front rotor. It uses a two piston sliding front caliper or the Subaru fixed 4-pot. The sliding caliper, bracket, and pad were changed in 03 and that's something you need to be aware of when upgrading from RS brakes or purchasing pads. The 4-pots are only on the 06-07 WRX in the US, though they were on many older non-US STis and WRXes (the black calipers with Subaru across them). Generally 16" wheels are required with these brakes but there are some 15" wheels out there that work. Also 16x6.5 Subaru wheels do not clear 4-pots. The other rotor I listed at 292 is a newer rotor on the Legacy and maybe like 11-14 WRX. They are a little heavier than the older 294mm parts and should be interchangeable.
Applications:
01 Legacy GT LTD?
02-04 Legacy GT
05-09 Legacy non-gt *
01-13 Outback
02-14 Impreza WRX (including 08, which uses 2-pots)
03+ Forester
Baja
BRZ/FRS/GT86
Here is the description on the different DBA rotors in this size:
Quote:
Originally Posted by WRXBrakes 
DATA
DBA 1 piece:
Standard series - p/n 650 - fits 2 or 4 piston WRX w/294mm rotor
4000 series - p/n 4650 - Again fits all 2 or 4 piston 'WRX' applications. However - some street pads w/ shims on them may not fit w/ the shim as the rotor is intentionally a bit thicker to add heat mass. Take shims off - run a few weeks - if it gets noisy wait till they can fit.
p/n 4000 - Original 4000 series rotor w/ tapered HAT section to clear OUTBOARD ABS tone ring. This ABS system is all pre-2000 MY afaik.
5000 series:
p/n 5000 -the OG - fits 4 pot WRX only
p/n 5010 - fits 2 pot OR 4 pot front WRX calipers. This rotor was made when it was realized that the caliper bracket from the USDM WRX hit the rotor hardware on p/n 5000. Thus 5010 has a different design- the hardware is recessed for clearance.
Added bonus points: This rotor is also available in 5x114.3 to make it possible to swap an 05-07 STi to the subaru 4-pots for rally. Not sure where to find that rotor but I would start with rally shops. A standard WRX rotor cannot be re-drilled to 5x114 as it won't fit over the larger hub.
*The non-turbo Legacy actually has a slightly different rotor that is technically 292mm in diameter. It is also slightly heavier than the WRX rotor. They can be interchanged without issue. Winn Dixie weekly ad organic food deals might be some good deals for this week's shopping.
294x28
This is a new rotor size on the 2015 Legacy 2.5i. It's the same diameter as existing rotors but a few mm thicker. I would be curious to see if this fits in the 4-pot caliper but I suspect it is a bit too wide. Comes in 5x114.3 only, so it would clear 05 sti front hubs.
316x30mm
This uses a two piston sliding caliper similar to the other 2-pots, although brackets and calipers aren't compatible between other 2-pots. 17s are required with them.
Applications:
05-09 Legacy GT
10+ LGT?
14+ Outback/Legacy (5x114.3)
Tribeca (5x114.3 bolt pattern)
2015+ WRX (5x114.3)
326x30mm (5x100)
326x30mm (5x114.3)
STi rotor that goes with the 4-piston Brembo calipers. There are two rotors, the 04 has a 5x100mm hub bolt pattern, 05+ uses 5x114.3. The calipers all mount the same way so you can attach front Brembos to other Subarus without trouble.
Applications:
04+ STi
BRZ with performance pack brembos
340x32
2018 STI 6-pot front brembos. Have not confirmed exact dimensions. may be 345mm dia, may be 30mm wide, but I think 340x32 is right.
A note about the SVX:
The SVX has brakes that are about the same size as WRX brakes and the SVX has 5x114.3 hubs. However, up front, the rotor hat offset (how close or far the rotor surface is from the hub) is different from that on other Subarus. The knuckle also locates the caliper bracket in a different position. That unfortunately means that you can't just buy some new 5x114.3 brakes to upgrade your SVX. I'm pretty sure that in the rear things are compatible with other Subarus.
I'm going to divide rear brake into two categores, what I call "old" and "new." The old brakes are on things like the 93-07 impreza and 90-09 Legacy. Brakes changed to the "new" style with the 2008 Impreza and 2010 Legacy. Old and new stuff will not interchange because the offset between the rotor hat and caliper changed. In some cases (like the STI), Subaru kept using the same rotor dimensions, but you can't, for example, stick a 2010 sti rear rotor on a 2005.
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Old rotors:
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266x10mm
The most common Subaru rear rotor on older cars. It uses a single piston sliding caliper, of which there are a few variations. Early Legacy sedans (non-turbo) and Imprezas have a smaller piston than Legacy wagons and turbos, and there are a few bracket/caliper revisions.
Applications:
90-99 Legacies/Outbacks with rear discs non-turbo
93-07 Imprezas with rear discs (except sti, 06-07 wrx)
98-08 Foresters with rear discs
274x10mm (old)
There are two versions of this rotor. One old, one new. The onld version went on 05-09 Legacy/Outbacks, with a 170mm parking brake. The exception is the LGT and 3.0R, which got 290x18mm vented rotors.
Applications:
05-09 Legacy/outback non gt (170mm brake, old style)
2012+ Impreza non-turbo
2014+ Forester 2.5i
290x10mm
This is well known as the H6 rear rotor. The Legacy caliper is the same as most other 99-07 1-pot Subaru calipers so you can upsize to this rotor simply by purchasing the brackets and correct pads.
The "H6" bracket is part number 26625AE000. It uses pad shape D770
Applications:
00-04 Legacy/Outback non-brighton
SVX (5x114.3, 190mm parking brake)
Ver5 STI type-RA (5x100, 190mm parking brake)
266x18mm
This is the Legacy turbo rear rotor. The caliper is similar to the other calipers but is wider to accomodate the vented rotors. I hear it was also found on the v1 WRX (93-94).
Applications
91-94 Legacy turbo
290x18mm (170mm parking brake)
290x18mm (190mm parking brake)
290x18mm (2010+ Legacy GT, BRZ)
There are actually three different rotors in this size, and they are available for new and old cars. The first is the standard 06-07 WRX and 05-09 LGT rotor. It uses either a 2-piston opposed caliper or a 1-pot slider. The 2-pot will not bolt up to other Subarus without something like the Kartboy brackets or having a new backing plate pressed onto the spindle. The next version is for the STi 190mm parking brake so that 2-pots can be used on rally cars. See below for more info on the "new" version.
Applications:
05-09 Legacy GT (1-pot, 170mm park brake)
06-07 WRX (2-pot)
04-07 STi with FHI 2-pot conversion
2010+ Legacy GT
BRZ/FT86/FR-S
Some older non-us spec-b Legacys and wrx/sti models (see rear brake redux)
Note: The LGT uses a different brake line than older Legacies and Imprezas. So I think you need to grind down part of the caliper where the line mounts to get it to work on an Impreza. The LGT lines are a different shape and mount and a different angle and you can't use them.
316x20mm (5x100)
316x20mm (5x100, 170mm parking brake)
316x20mm (5x114)
STi brembos. There are multiple versions of this disc. One for the 04 STi, one for 05-07, one for 08+ and one with a 170mm parking brake drum. There's an explanation how to install rear brembos on other cars a little farther down. 08+ sti rear rotors have a different backspacing.
Applications
04+ STi
320x18mm
Tribeca rear rotor. 190mm brake, 5x114.3. Strangely, this rotor appears to have the "old" offset despite being on the new rear suspension. Tesco offers are ready for browsing today.
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New rotors
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274x10mm (new)
I mentioned this size already, the new version goes on new cars with 170mm parking brakes, which for some reason came back around 2012
Applications:
2012+ Impreza non-turbo
2014+ Forester 2.5i
286x10mm
New style rotor only, probably the most common one. Uses a 190mm parking brake. Also found on 2015 wrx in 5x114.3
2008-2014 wrx
2009-2013 forester (with rear discs)
2010-2014 Legacy 2.5i
Some BRZ/FRS/GT86 models (in non-us markets only)
2015 WRX - 6MT only
uses a 190mm parking brake and 1-pot sliding calipers.
Why are there a 274x10 and a 286x10 rotor used on the same cars? Because the 274mm has a 170mm parking brake, the 286mm rotor has a 190mm parking brake. That doesn't really answer why they decided to go back from 190 to 170 on the impreza for 2012.
278x18
New vented rear rotor on the 14+ Forester XT. Probably has a 170mm brake, but is vented. Would be an upgrade for cars with 274x10mm rotors.
290x18mm (2010+ Legacy GT, BRZ)
Also mentioned above, the new version of this rotor is for 08+ cars with a 190mm parking brake. It can be found on the 2010+ LGT and the BRZ/FT86/FRS. This third version could also be used as an upgrade for the 08+ Impreza and wrx if you wanted to go to slightly larger vented rotor. It does not interchange with the group n rotor. There is a bracket from KNS brakes to use this rotor with the old 2-pots on the new cars as well.
Applications:
2010-14 Legacy GT
BRZ/FT86/FR-S
300x17
New larger and vented rear rotor for the 2015+ legacy, outback, and WRX with the electronic parking brake. The parking brake is done by the caliper so I'm not sure about upgrading to these. I don't think they have the appropriate drum in the hat for a mechanical parking brake but you could probably use a BRZ caliper on the brackets for them.
316x20mm (5x114)
08+ sti rear rotor, 190mm drum, new offset. With a redrill will work on 08+ wrx, and the rotor and caliper should go right onto a 15+ wrx if you wanted.
Applications
08+ STi
326x20
2018 sti rear rotor, little bigger than the old one.
Drums
Some cars have rear drums that are like 9." I don't really know anything about Subaru drum brakes so it would help if someone filled that stuff in.
Some of them are: Legacy and Impreza Brighton models, Some 95-99 Legacy L models, some foresters and I think 02+ Impreza TS and OBS. (I'm not sure exactly)
To swap out drums, at the least you will need new parking brakes, backing plates, discs, calipers, and brake lines. It is usually best to get a whole knuckle/hub/parking brake assembly out of a car with rear discs. If you want to put rear discs on your front wheel drive Subaru, you might have to parts from a 90-94 Legacy, since they might be the only FWD Subarus with rear discs and the FWD rear hubs/spindles/struts/etc are different.
Installing rear Subaru 2-pots or Brembos on a non 2-pot car:
The Subaru and Brembos have the same backing plate, which is different from all the other Subaru rear disc backing plates. So calipers don't swap between the two. Additionally, the STi uses a 190mm parking brake drum. Pretty much everything else uses a smaller 170mm drum. That means if you take a set of rear brembos and put them on your WRX, the parking brake will not work.
However, there are Subaru 2-pot rotors (290x18mm) with a 190mm parking brake hat and Brembo rotors (316x20) w/ a 170mm e-brake so you can put either setup on either car. There are also Kartboy brackets that will adapt the 2-pot calipers to any other Subaru, and since both rotors are available in 170mm parking brake variety, you can swap either one onto any other Subaru.
Here's a threadabout fitting the brembos to other cars with the new Kartboy brackets and DBA rotors.
Here is the rear brake redux, which has more information about the older rear brakes that came on STis and fancy Legacys in Japan.
Some D-plate numbers
Quote:
Originally Posted by stoptech
The Friction Materials Standards Institute (FMSI) is an association that assigns numbers to different pad shapes that are used as a guideline for pad manufacturers to refer to, and bring a common numbering system to the brake pad aftermarket. Virtually every pad manufacturer will either use the FMSI number in their numbering system or have a readily available interchange to cross-reference their part number to the FMSI number.
I should note that the caliper bracket, and not the caliper, is what determines pad shape. So while there are a few different pads, in some cases the calipers are the same.
Front 1-pots D470:
1990-1995 Legacy
1993-1996 Impreza
D722:
1996-1999 Legacy
1997-2001 Impreza
D563:
1991-1994 Legacy Turbo
1996 Outback
1996 Legacy GT
D721:
1997-2002 Legacy
1998-2001 Impreza RS
2002 Impreza and WRX
1998-2002 Forester
D929/D1539:
2002-2009 Legacy/Outback (non-gt)
2003+ Impreza/Forester
8/2002-2005 WRX
2008-2014 WRX
BRZ/FRS/GT86
I added a new shape, 1539. It is listed specifically for the 11+ but the basic shape is still the same. Difference is that the new pad has more friction material on it and slightly different wear indicators.
See this article for clarification on 02-03 shapes
D1078:
2005-2009 Legacy GT
Tribeca
2015 WRX
D471:
1990-1999 Legacy
1993-1998 Impreza
1993-1997 SVX
D770:
2000-2004 Legacy
2005-2009 Legacy GT
1999-2002 Impreza
D1004:
11/2002-2005 WRX
2003-2007 Impreza
D1114:
2005+ Legacy 2.5i/Outback (incl 2010+)
2008-2011 Impreza
2008+ WRX (includes 2015)
2009+ Forester
non-vented FRS/BRZ/86 rear brakes
D1124:
2010+ Legacy GT
FRS/BRZ/GT86
D1808:
15+ Legacy
15+ WRX with cvt/eyesight
Front: D647 (or D1170, D460, D1182)
Rear: D461
Front: D1001
Rear: D961
Front: D1365
rear: D6027
note: The front pads are found on some Lexus and AMG models so aftermarket stuff is already available. It was first thought that the rear pads were shape 1366, which existed, but closer comparison seems to indicate that is not the case. Centric currently lists 104.60270 and there are a few pads now available.
Missing information:
- non-us market vehicles
Why Are Brake Calipers on the Back of Rotors
Source: https://forums.nasioc.com/forums/showthread.php?t=1265631
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