Brake interchangeabililty info

[jamal]

Is interchangeability a word? I guess so since there's no squiggly red line under it. Anyhoo, while I touched on this stuff in the compiled brake information thread, I thought maybe it couldn't hurt to have it all laid out a little more clearly.

Basically, most Subaru brakes will interchange onto other Subarus. That's very convenient when you want to put bigger brakes on your non-STi Subaru without spending a lot of money. To be extra clear, almost any front caliper will bolt onto any other Subaru. The rear brakes are where things get complicated.

When talking about physically bolting the brakes up to another Subaru, there are a few things to be concerned about:

1. Wheel Clearance
2. Rotor bolt pattern
3. Caliper mounting
4. Rear parking brake diameter

#1 is pretty simple. If you're putting brembos on your 93 Impreza L, obviously the the tiny stock steelies aren't going to fit.

#2 is something you have to be concerned with when installing brembos. The 05+ STi has a 5x114.3 bolt pattern. So while you can bolt the calipers right up other cars, you'll need to use rotors drilled in 5x100, such as those on the 04 sti. The Tribeca and SVX also have a 5x114.3 bolt pattern, while all the other Subarus since 1990 or so are 5x100 (well, except the Justy).

#3 comes into play when installing STi brembos or the Subaru 2-pots in the REAR. Any FRONT caliper/bracket will bolt up to the front of any other modern Subaru (except the SVX), but in the rear there are different backing plates. The backing plate is attached to the rear spindles, and is what the calipers bolt to. There are a few different backing plates, and brakes will not interchange between them. The solution is to either switch backing plates or use an adapter bracket.

The way to divide up the backing plates is as follows:
-Drums
-Sliding 1-pot calipers
-Fixed 2-pot calipers
-new cars - 08+ impreza, 09+ forester, '10+ legacy, which do not have a backing plate.

drums

Obviously you can't bolt discs up to a drum backing plate since there's nowhere for the caliper to attach. To swap from drums you'll need to remove the brakes, press out the hub, remove the backing plates, and install disc backing plates, parking brakes (also the cables), the hubs (and likely new bearings), and then rotors and calipers. Generally it's easier to find some disc spindles and swap the whole things over.

1-pots

For the sliding calipers, almost everything is interchangeable. That includes everything from a 1990 Legacy to Imprezas and Tribecas and even the SVX (although bolt patterns may vary). For example, if you have an 02-05 WRX, you easily swap on the bigger Legacy brakes without any special parts or extra work.

2-pots

To bolt a 2-pot rear caliper to a 1-pot car, you'll need to install either the 2-pot backing plates which is the same process I mentioned for drums, or you can purchase some adapter brackets. WRXbrakes, Kartboy, and a few other places make conversion brackets to attach either the Subaru 2-pots or 04-07 Brembos to the rear of most any other Subaru. I should note that WRX 2-pot rear adapters do not work with Brembo 2-pot rear calipers even though the mounting is the same between them.

If you want to swap rear brembos for the 2-pots, or vice-versa, no bracket is required. Sti brembos will bolt right up to an 06-07 WRX, and the rear 2-pots will bolt right up to an 04-07 STi.

If, for some reason, you wanted some sliding calipers on your 2-pot car, you're out of luck. No bracket exists so you'll have to pull off the spindles and swap backing plates.

When it comes to STi Brembos, there's another little issue that arises when switching brakes and that is the rear parking brake. The STi, along with a few non-US models, has a larger 190mm parking brake drum (compared to 170mm on everything else). That means if you were to pick up some rear STi brembo calipers and rotors and put them on your non-sti, the parking brake wouldn't work because there's a 10mm gap between the drum and the shoes. It also means if, for rally purposes perhaps, you wanted some Subaru 2-pots on your STi, the rotors wouldn't fit over the parking brake.

Thankfully there's a solution for each situation. Subaru took care of the Brembo -> 2-pot swap because the 2-pots are (were) the group N rally-spec brakes. So they make rotors that work with the 2-pots but fit over STi parking brakes, in both 5x100 and 5x114.3. You can get them from rally shops such as Rallispec or Rocket Rally.

To make rear brembos work on a 170mm parking brake car, there are a couple of solutions. The best one is the DBA 2657 rotor. It's a brembo-sized rotor, drilled for 5x100, with a 170mm parking brake hat. This is a new thing that was produced specifically to go with the WRXBrakes Brembo adapter brackets, so be sure to thank Tom and DBASteve and Ken at WRXbrakes for getting together on that.

Before then, the solution was to either swap to a bigger parking brake, get some spacers made to fit in the rotor hat, or buy some taller parking brake shoes. Godspeed in the UK makes taller shoes, and adapter brackets. Brembo also makes adapter brackets and rotors, but I am unsure on pricing and availability on them.

Can I put front brakes on the rear?

No, as in not a chance. Don't try. Don't post a thread asking about it.

What happens to my brake bias?[/b]

If you have a 93 impreza and put on some front brembos, you might think that there would be a big increase in braking force. You would be right, and it would only be on the front wheels. That results in the front doing all the work, the rear doing nothing, and can actually increase your stopping distance. If you are swapping brakes around, take a look at this spreadsheet:

http://www.main.experiencetherave.com/s ... kemath.xls
courtesy of Legacy777

Ideally you want to keep the bias where it was or go rearward a small amount (why the H6 upgrade is so popular).
new cars


For 2008, the Impreza has a whole different thing going on in the rear. While the front brakes are still the same, the rear suspension, spindles, and caliper mounting changed on regular Imprezas, the WRX, and the STi. Instead of a backing plate, the calipers mount to the spindle just like the front. Because of this, the calipers are different. The bolt spacing is actually the same as older 1-pot calipers, on both the WRX and STi.

Another thing to note is that the 08 WRX has the same larger 190mm parking brake hat as the STi.

So yes, it is possible to put 08 sti rear calipers on an 08+ wrx and it happens to be very easy. All you need is any set of front brembos, 08+ sti rear brembo calipers, and rotors drilled for 5x100. You can use 04 sti front rotors, but 04 sti rear rotors won't work and they have to be for an 08+ STi. Pretty much any machine shop will be able to re-drill the rotors for a nominal charge. What's even more convenient is that DBA dual drills their STi rotors in 5x100 and 5x114.

This will only work with 08+ sti rear calipers and re-drilled 08+ STi rear rotors because the mounting on the calipers changed as did the rotor hat offset. If you were to attempt to use an 04 sti rotor, it would not line up with the caliper. The DBA rotor part numbers are 4654 front and 42656 rear. Anything dual drilled will have the part number end with -10. For example, DBA42656XS-10 is the dual drilled rear rotor that would be good to use for this swap.

The 09+ Forester and 2010+ Legacy (and BRZ) also has the same rear upright and brake setup, so all this should apply to them as well.

If you wanted to put 08 sti rear calipers on an older 1-pot cars, they would bolt to the backing plate, but there is no rotor that will currently work. The DBA rotor would not line up with the caliper. The actual difference in offset is something I don't currently know, and I'm not sure if even an 08 sti rotor re-drilled would line up properly (parking brake issues aside). It could end up interfering with the backing plate.


Exceptions to the rules

-If you want to put smaller brakes on an STi, you can't just take a regular wrx front rotor, re-drill it, and bolt it on. The rotor hat will not fit over the hub. Subaru make special rotors to do this.
-If you have an SVX, the front brakes are different and don't interchange. Rears are H-6 sized, but get that added rotor size at the upright and not from the bracket. You should be able to bolt on newer 1-pot rear brackets and calipers if you were looking for replacement parts but there isn't really an upgrade that works.


NEW: My best guess about the Subaru BRZ.

The upcoming BRZ uses the same rear suspension as the current Impreza/Legacy. So, putting Brembos on (something Greddy has already done), is the same as for the 08+ WRX- you take the STI caliper, redrill the rotor, and it bolts right up.

In the front, things are almost as simple. The calipers bolt to the uprights, so you would just need 04 sti rotors and any calipers. There is one extra thing you have to do though: because the calipers mount to the leading edge of the upright, the bleed screws have to be swapped to the other side of the caliper (not all that difficult). We can't just put the calipers on opposite sides because the piston sizes are staggered and you would end up with crazy uneven pad wear. And you obviously can't have the bleed screws facing down either.

[greg donovan]

i am buying a 93 impreza wagon with drums out back.

i want to swap the front and rear brakes from my 94 SS onto the Impreza.

aside from swapping rear spindles and the brackets rotors and calipers what else do i need to do in the back? are the brake lines different from disc to drum in the rear?

[beanis05]

This should be a sticky

[jamal]

I think there's a link to it in the faq. Actually that reminds me to update it.