Better braking system

scottzg · Post by **scottzg** » Mon Oct 27, 2003 6:52 am

Could this be the ultimate budget sedan brake setup?

Legacy turbo wagon rear brakes (larger piston than sedan) And wrx front brakes.

My thinking is that the wagon pistons will offset the front brake bias of the wrx.

From what i hear, turbo rears and wrx rears are the same size, but the wrx is not vented. WRX fronts w/ n/a leg rears gives goofy brake bias.

THAWA · Post by **THAWA** » Mon Oct 27, 2003 7:40 am

That reminds me, I went o the yard the otherday and looked at a turbo they had there. It had drums in the rear, what's that all about?

Post by **Legacy777** » Mon Oct 27, 2003 3:04 pm

I don't know if I'd use the word ultimate.....but it's a good setup.

Couple things I would like to correct though.

The turbo legacy rear caliper piston size is the same, regardless of wagon or sedan. The n/a legacies however are different. The sedans do have a smaller rear piston. The wagons' pistons are the same size as the turbo models.

The WRX rear pistons are most definitely the same size as the turbo legacy rear calipers. The standard rear caliper piston size for pretty much all newer subies is 1.5" dia. The only way you can get more rear brake torque is to go to the "H6" Legacy style rear caliper bracket, or get the 2pots in the rear.

As for the bias issue. I had WRX fronts, & turbo legacy rears, and the bias was still too much to the front. I swapped to a wagon prop valve. That helped some....but I still could use a little more rear bias. If I had it to do all over again, i would've gone with the H6 conversion in the rear, rather then the turbo legacy vented rotors.

vrg3 · Post by **vrg3** » Mon Oct 27, 2003 3:19 pm

Yeah, "ultimate" is a bit strong. There are plenty of big brake kits for the WRX that would probably outperform this setup easily even with the heavy front bias.

The "H6" upgrade (a misnomer, since the same rear brakes are on all newer Legacy wagons, I think) is pretty good except that it doesn't fit as nicely as the vented rear brakes, since you have to trim the backing plate and stuff like that.

Apparently some JDM models actually had vented rear brakes with the same diameter as the "H6" brakes. Sounds pretty cool.

Josh, have you considered trying an aftermarket proportioning valve setup? It looks like most aftermarket ones are designed for single-channel brake systems, but maybe you could use two in parallel? Wilwood has a lever-style one that clicks into one of 6 positions, so I would expect that if you used two of those set to the same position it would work. You would just have to adapt your car's fittings to 1/8" NPT (I'm sure a little bit of searching through an Earl's catalog would find you everything you need).

You may actually be able to put these in series with the stock wagon prop valve you have now...

scottzg · Post by **scottzg** » Mon Oct 27, 2003 7:37 pm

"ultimate budget"

hmm, so the aforementioned setup with a couple variable proportioning valves, perhaps?

Post by **Legacy777** » Tue Oct 28, 2003 3:05 am

I looked into aftermarket. There are no dual channel setups. Even with two valves....the chances of getting both set to EXACTLY the same is very slim.

Even with higher prop valve split point, it wouldn't affect braking at lower brake pressures.

vrg3 · Post by **vrg3** » Tue Oct 28, 2003 4:13 am

Well, at lower pressures (below the split point), don't all four calipers get the same pressure anyway?

You could ask Wilwood about the lever-style valve; it is possible that they design them to tight tolerances so that any particular setting is very predictable when you compare one valve to another. Or, it's possible that they'd vary widely.

If what you're really looking for is more pressure to the rear than to the front (at low master cylinder pressures) maybe you could set up another valve coming right off the master cylinder, in effect putting a prop valve on the front wheels as well. I think I'm confusing myself now though...

Post by **Legacy777** » Tue Oct 28, 2003 3:07 pm

I've emailed tilton, and/or a couple other suppliers of those prop valves. Even if tolerances would be tight enough, I'm not replumbing my brake lines.

Yes, below the split point, all four brakes get the same pressure.

The thing about my setup is that I really have not physically increased brake torque. I merely adjusted the split point, and in effect have a perceived increase in rear brake torque because pressure is slightly higher. Typically when doing brake torque/bias calcs, you don't take brake pressure into account.

The only way to physically increase brake torque is with larger rotors or larger caliper pistons.

I really don't want higher pressure at low MC pressure, I want an increase in brake torque in the rear, along the entire braking force curve.

vrg3 · Post by **vrg3** » Tue Oct 28, 2003 4:01 pm

Ah, then that definitely means bigger brake hardware in the rear... Or going back to smaller in the front.

You wouldn't have to do that much replumbing; you can get adapters and everything so that it could be plug and play except that you'd have to mount the prop valve(s) somewhere.

Post by **Legacy777** » Wed Oct 29, 2003 3:01 am

I'd have two lines to deal with and four compression type fittings to deal with that would need to be Y'd or connected up.......no thanks

Yeah, Impreza RS rotors up front would probably be a near perfect setup.....or close to being good.

evolutionmovement · Post by **evolutionmovement** » Wed Oct 29, 2003 6:45 am

Thawa- There were earlier stripper Legacies that came with unpainted bumpers and had rear drum brakes, but was the one you saw just missing the rotors and had the drum parking brakes underneath exposed in the rear?

Steve

THAWA · Post by **THAWA** » Wed Oct 29, 2003 7:10 am

That's kinda what it looked like. It didn't look like any other drum brakes I'd seen where the drum filled the whole thing, it looked like there was part of a disc rotor there so that's probably what it is. So do all cars with rear discs have drums under them aswell or is this just dependant on the manufaturer?

evolutionmovement · Post by **evolutionmovement** » Wed Oct 29, 2003 7:41 pm

Most cars have the disc/drum combo, but old Subarus like my '84 GL's actually just used the front calipers as parking brakes. They were terrible for leaving burns on the rotors after a hard drive and they made hand brake turns impossible, but they're why I learned smoothe imputs and conservation of momentum (something you need with 73 hp and 90 lbs./ft anyway). Someday I'll find a nice 2-door 5MT...

There were some other cars that did this, too, but i can't think of what they were.

Steve

yazmo · Post by **yazmo** » Tue Jul 14, 2009 11:18 pm

hi can i ask a question?

what is H6 conversion braket with stock rotor? which 2pot piston from what year and model of subaru?

i have to change my rear setup this week so i am looking for an ubgrade

thx in advance

93forestpearl · Post by **93forestpearl** » Wed Jul 15, 2009 2:35 am

If you are looking for 2 pots in the rear it is going to be expensive. To run subaru 2 pots in back you need different backing plates, and you should replace the bearings since you need to press the hubs out to remove the backing plates.

Or, I think it is Kartboy that sells adapter brackets to add 2 pots to regular backing plates. It saves you about $25 and a lot of hassle.

Although, if you are on stock front brakes, there really is no point to adding 2 piston calipers to the rear. I'd consider going to a vented setup from the turbo car. Or just get pads, because pads will be the single largest improvement to your braking.

yazmo · Post by **yazmo** » Wed Jul 15, 2009 10:21 pm

thx you ill consider this, my rotor are definitly wear too much on the back so im going for a replacement, but here i cant find axxis or hawk hp+ pads nowhere.

anyone know where i can find these!

conrAWD · Post by **conrAWD** » Tue Nov 10, 2009 9:02 am

yazmo wrote:thx you ill consider this, my rotor are definitly wear too much on the back so im going for a replacement, but here i cant find axxis or hawk hp+ pads nowhere.

anyone know where i can find these!

Check r1concepts.com - I found them to have some pretty cheap brake parts (especially rotors) and free shipping over $150.

Also, buybrakes.com is a great site with tons of pads.

To the rest, I need to change my brakes after 1 year of running EBC red stuff pads and I'm not sure where to go with my system. I was planning on sticking with the Turbo Legacy vented rears and upgrading the fronts to WRX 2pots.

How bad is the front bias? Should I scratch the idea and stick with the stock rotors up front?

Also, I believe there is a link to a brake bias calculator in one of the sticky's in this forum. It is an excel spreadsheet which can tell you how much your braking will change with the different set up. According to this equation my brake bias will increase by 8.24%

Post by **Legacy777** » Tue Nov 10, 2009 8:48 pm

The bias change is only a few percent. The brake torque change is what is around 8.24%. The spreadsheet's mine.

As for "how bad" is the front bias.....that really depends on the driver. Brake bias feel is really a subjective thing. Engineers can design the car for maximum braking force to be applied via the amount of grip available at the tires, but to different people the feel may be varied.

Personally, what I would probably recommend is the WRX front 2-pots and H6 rear upgrade. If you have the money, go with the Subaru 4-pots & 2-pots. Only downside to the 4-pots is that most stock subaru 16" wheels will not clear them.

Subaru_Nation555 · Post by **Subaru_Nation555** » Wed Nov 11, 2009 4:03 pm

Legacy777 wrote:As for the bias issue. I had WRX fronts, & turbo legacy rears, and the bias was still too much to the front. I swapped to a wagon prop valve. That helped some....but I still could use a little more rear bias. If I had it to do all over again, i would've gone with the H6 conversion in the rear, rather then the turbo legacy vented rotors.

I'm in the same boat, even with those upgrades there is too much frontward bias. By "H6 upgrade" do you just mean the H6 rotors and caliper brackets running Legacy Turbo calipers?

Post by **Legacy777** » Wed Nov 11, 2009 5:03 pm

Unfortunately, the H6 calipers are different then turbo legacy rear calipers. So you would need to pickup a set of H6 calipers as well as the brackets.

If you must have vented rear rotors, you can upgrade to the new Legacy GT rear vented rotors. They are the same diameter as the H6, but are vented.

jdmellor28 · Post by **jdmellor28** » Sat Feb 13, 2010 7:06 am

has anyone just taken out the rear proportioning valve and tried that out ?

would bad things happen ?

ciper · Post by **ciper** » Sun Feb 14, 2010 1:04 am

Your rear wheels would probably lockup constantly unless you drive backwards lol
A well known company in the Subaru community, who shall remain nameless, thought they could do this when they built one of the first race prepped 2008 STI. I literally said the rears would lock to one of their engineers TWICE before they got on the track because I noticed they had replaced the proportioning valve with a shiny useless piece of machine aluminum which acted purely as a "splitter"

Guess what happened - They locked up the rear wheels on every turn. What a waste of tires and time

jdmellor28 · Post by **jdmellor28** » Sun Feb 14, 2010 7:38 am

note to self : DO NOT REMOVE THAT PART !
hahaha

thanks ! im just dumb enough to do something like that .. glad i asked first !

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Better braking system

Better braking system