GT Brakes on standard Legacy?

[bpimm]

Do the larger Legacy GT rotors and calipers fit the standard legacy? I have 16" Wheels already. What about the 4 piston wrx calipers?

Thanks
Brian

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[Jonathan]

What model Legacy are you using ?

I am in the process of getting parts to convert my 1996 Legacy "L" (Front disc, Rear Drums) to a four wheel disc braking system.

My understanding is for the front you want to replace the front single piston calipers to the dual piston calipers and get the slightly larger Rotors and backing plates (The backing plate is what the calipers bolt on to). If you use 2nd generation Legacy (95-99) parts you can use 15" or 16" wheels. If you spring for the WRX parts you MUST use 16" wheels as the rotor, and backing plate are slightly larger. (15" wheels will not clear the calipers)

I wasn't aware that the stock WRX used 4 piston calipers.

Has anyone done a Legacy drum to RS/WRX Rear disc swap ?

[subysouth]

To give you the best advice we would need to know what exact setup you are starting with because you need to consider how swapping calipers/rotors will affect brake bias.

If its the single piston front calipers they should be on 260mm rotors.

Where are you located? If your WRXs come stock with 4pots, likely somewhere other than the US.

ss

[subysouth]

Originally Posted by Jonathan

What model Legacy are you using ?

I am in the process of getting parts to convert my 1996 Legacy "L" (Front disc, Rear Drums) to a four wheel disc braking system.

My understanding is for the front you want to replace the front single piston calipers to the dual piston calipers and get the slightly larger Rotors and backing plates (The backing plate is what the calipers bolt on to). If you use 2nd generation Legacy (95-99) parts you can use 15" or 16" wheels. If you spring for the WRX parts you MUST use 16" wheels as the rotor, and backing plate are slightly larger. (15" wheels will not clear the calipers)

I wasn't aware that the stock WRX used 4 piston calipers.

Has anyone done a Legacy drum to RS/WRX Rear disc swap ?

Jonathan the front brakes bolt directly to the front knuckle, not a backing plate. There is also a minor dust shield bolted to the front knuckle as well but it doesnt HAVE to be swapped when upsizing rotors. All Subaru front calipers I have ever seen since 1990 use the same front caliper bolt spacing and all will bolt up to any Subaru front knuckle. You could bolt 04 STi front Brembos to a 1990 Legacy L for instance.

The rear calipers do have a backing plate(its bolted to the rear knuckles) to which the calipers attach and there are several varieties of these plates based on application:

single pot rear with 170mm handbrake(most common)
single pot rear with 190mm handbrake
2pot non-Brembo with 170mm handbrake
2pot non-Brembo with 190mm handbrake
2pot Brembo with 190mm handbrake

ss

[bpimm]

Jonathan]What model Legacy are you using ?

My Legacy is the L model it has the single pot calipers.

Jonathan]I wasn't aware that the stock WRX used 4 piston calipers.

subysouth] Where are you located? If your WRXs come stock with 4pots, likely somewhere other than the US.


I think the 4 pot I read about were JDM calipers. I'm Washington State, USA.

If I'm reading this right, any factory brakes will bolt on the front. providing my wheels are big enough. and on the rear I may need to change the backing plate.

I'll measure mine out this weekend to see where I'm starting, I have to get better brakes on this thing. I live at 1200 Feet elevation and drop to 200 feet in about a mile on a tight twisty road.

Thanks
Brian

[ooberdoob]

see that QUOTE button in the bottom corner of each post? you can use that to reply to questions, etc if you like. i didn't know if you had noticed it... it took me... too long to see it.

i vote go directly to the subaru 4pots. might as well go for the good stuff. if i had the $ i would, and i have a 98 GT my brakes are ok, but there is much better thats for sure.

[subysouth]

Originally Posted by bpimm

Jonathan]What model Legacy are you using ?

My Legacy is the L model it has the single pot calipers.

Jonathan]I wasn't aware that the stock WRX used 4 piston calipers.

subysouth] Where are you located? If your WRXs come stock with 4pots, likely somewhere other than the US.


I think the 4 pot I read about were JDM calipers. I'm Washington State, USA.

If I'm reading this right, any factory brakes will bolt on the front. providing my wheels are big enough. and on the rear I may need to change the backing plate.

I'll measure mine out this weekend to see where I'm starting, I have to get better brakes on this thing. I live at 1200 Feet elevation and drop to 200 feet in about a mile on a tight twisty road.

Thanks
Brian

Unless you want to go real exotic(2pots or SVX brakes for some reason), you wont need to change rear backing plates.

What model is you Legacy and we can tell you what brakes you should have.

ss

[Jonathan]

Originally Posted by subysouth

What model is your Legacy and we can tell you what brakes you should have.

I beleive that bpimm mentions that he has a 1998 Legacy "L" which has the single piston front calipers and slightly smaller front rotors and rear drum brakes. (?) I could be wrong on this though.

I am assuming that bpimm will be swapping out his tiny front rotors for the slightly larger Legacy GT or even bigger WRX front rotors AND will be utilizing the two piston front calipers. Assuming he were to stick with the stock size rotors then yes he can just bolt on the two-piston calipers, but IF he is indeed getting the larger rotors, he will need to alter the mounting point of his calipers.

Originally Posted by subysouth

Jonathan the front brakes bolt directly to the front knuckle, not a backing plate. There is also a minor dust shield bolted to the front knuckle as well but it doesnt HAVE to be swapped when upsizing rotors.

To the best of my knowlege (which may be faulty) the calipers attach to what i would call a backing plate that he will need to have swapped in order to properly fit the larger diameter rotors. I will be double checking my information here, as I do not wish to give out faulty/bad advice.

At any rate if you install larger front brakes, you should also upgrade the rear brakes as well so as to keep the effective front/rear braking balance the same.

[bpimm]

Originally Posted by subysouth

Unless you want to go real exotic(2pots or SVX brakes for some reason), you wont need to change rear backing plates.

What model is you Legacy and we can tell you what brakes you should have.

ss

1998 L 4 dr sedan

I don't want to go exotic, I just want brakes that will stop me and not warp the rotors.

I will be autocrossing it some so better performance is desirable however I don't want to take out a second mortgage to fund the brakes.

Brian

[subysouth]

Originally Posted by Jonathan

I beleive that bpimm mentions that he has a 1998 Legacy "L" which has the single piston front calipers and slightly smaller front rotors and rear drum brakes. (?) I could be wrong on this though.

I am assuming that bpimm will be swapping out his tiny front rotors for the slightly larger Legacy GT or even bigger WRX front rotors AND will be utilizing the two piston front calipers. Assuming he were to stick with the stock size rotors then yes he can just bolt on the two-piston calipers, but IF he is indeed getting the larger rotors, he will need to alter the mounting point of his calipers.


To the best of my knowlege (which may be faulty) the calipers attach to what i would call a backing plate that he will need to swapped in order to properly fit the larger diameter rotors. I will be double checking my information here, as I do not wish to give out faulty/bad advice.

At any rate if you install larger front brakes, you should also upgrade the rear brakes as well so as to keep the effective front/rear braking balance the same.

Missed the L model part.

If its an L, it has single piston front calipers with 260mm discs and rear drums.

A tricky upgrade to maintain or improve on bias. I would recommend searching for posts on this topic in the brakes forum.

Jonathan, re-read my above post. Front calipers do not bolt to backing plates, they bolt directly to the front knuckles. All variance for rotor size is made up in caliper braket height(sliders) or mounting ear height(opposed.) The rears as I noted do use backing plates, largely as a mounting surface for the drum handbrake internals.

ss

[Jonathan]

Originally Posted by subysouth

Jonathan, re-read my above post. Front calipers do not bolt to backing plates, they bolt directly to the front knuckles. All variance for rotor size is made up in caliper braket height(sliders) or mounting ear height(opposed.) The rears as I noted do use backing plates, largely as a mounting surface for the drum handbrake internals.

Yes. I was wrong. Sorry about that.
Ravensblade-imprezza did an article on uprgading the older Impreza RS to the newer WRX brake setup sometime ago. I beleive the older style (Pre-2001 CG8) RS's utilized the same front braking setup as the Legacy GT. This article specifically mentions "caliper brakets" (not "backing plates") which are larger on the WRX to accomadate the larger rotor size.

http://www.northursalia.com/m.../wrxbrake.html

[subysouth]

Originally Posted by Jonathan

Yes. I was wrong. Sorry about that.
Ravensblade-imprezza did an article on uprgading the older Impreza RS to the newer WRX brake setup sometime ago. I beleive the older style (Pre-2001 CG8) RS's utilized the same front braking setup as the Legacy GT. This article specifically mentions "caliper brakets" (not "backing plates") which are larger on the WRX to accomadate the larger rotor size.

http://www.northursalia.com/m.../wrxbrake.html

No need to apologize, you live you learn.

ss

[bpimm]

Originally Posted by subysouth

Missed the L model part.

If its an L, it has single piston front calipers with 260mm discs and rear drums.

A tricky upgrade to maintain or improve on bias. I would recommend searching for posts on this topic in the brakes forum.

ss

Actually it has rear disk that I am planning to upgrade. but the warped fronts have to go now.

Brian

[subiekid]

Most people sell WRX brakes for around 250. You need caliper brackets, calipers, and rotors. If you can try and get the stock heat shields from a WRX it would also make the project a little easier. You could also upgrade to SS lines since you will have to bleed the system any ways.

What size of BMC do you have? Is it a two port BMC?

Since you have rear drums you will also need to get the rear hub from the car that you are getting the brakes from. I would just go with WRX parts because they are easier to find than GT parts.

[bpimm]

Originally Posted by subiekid

Most people sell WRX brakes for around 250. You need caliper brackets, calipers, and rotors. If you can try and get the stock heat shields from a WRX it would also make the project a little easier. You could also upgrade to SS lines since you will have to bleed the system any ways.

What size of BMC do you have? Is it a two port BMC?

Since you have rear drums you will also need to get the rear hub from the car that you are getting the brakes from. I would just go with WRX parts because they are easier to find than GT parts.

Thanks subiekid,

Thats what I was thinking, I'll have to hit the salvage yards and see what I can find. It already has disk on the rear so I will upgrade them later.

Ok I'm drawing a blank, What's a BMC?

Brian

[subysouth]

Doh, looked at the wrong column.

98 L:
single pot fronts with 260mm rotors
single pot rears with 266x10mm rotors

You are gonna need to upgrade the rears as well if you upgrade the fronts.

Going from your fronts to:

277mm/2pots(Leg GT,RS et al) = +21% front torque
294mm/2pots(WRX et al) = +30% front torque
294mm/4pots(non-Brembo) = +17% front torque

The Subaru chassis is already overly front biased, as you can see from the above improving only the fronts seriously worsens this situation. You will likely increase your stopping distances and may have pre-mature front lockup.

I would try to do the rears first.

ss

[bpimm]

Originally Posted by subysouth

Doh, looked at the wrong column.

98 L:
single pot fronts with 260mm rotors
single pot rears with 266x10mm rotors

You are gonna need to upgrade the rears as well if you upgrade the fronts.

Going from your fronts to:

277mm/2pots(Leg GT,RS et al) = +21% front torque
294mm/2pots(WRX et al) = +30% front torque
294mm/4pots(non-Brembo) = +17% front torque

The Subaru chassis is already overly front biased, as you can see from the above improving only the fronts seriously worsens this situation. You will likely increase your stopping distances and may have pre-mature front lockup.

I would try to do the rears first.

ss

I will look for a WRX to scavange for parts, I'm going to do all four but the fronts are first, the existing rotors are warped and have to be replaced asap.

Thanks for all the info.

I'll assume its the same for my son's 92 Legacy L also. He's standing behind me drooling right now.

Brian

[Jonathan]

Originally Posted by subiekid

What size of BMC do you have? Is it a two port BMC?

Originally Posted by bpimm

Ok I'm drawing a blank, What's a BMC?

Brake Master Cylinder might be a good guess.

[subysouth]

Originally Posted by bpimm

I will look for a WRX to scavange for parts, I'm going to do all four but the fronts are first, the existing rotors are warped and have to be replaced asap.

Thanks for all the info.

I'll assume its the same for my son's 92 Legacy L also. He's standing behind me drooling right now.

Brian

Lemme try to explain the larger picture. You need to maintain stock bias or somewhat increase rear torque compared to the fronts to improve braking performance. There are two sources for brake torque from the braking system, one fixed or inherent and the other variable. The above stats are for inherent or fixed changes based on increasing piston area and/or effective disc radius. The variable component is pad coefficient of friction.


The inherent torque increase of going with the "H6"(short term for the 2000-04 Legacy rear setup using the 290x10mm rotors) rear versus your stock rear setup would be ~+10%. And adding 10% to the rear torque is about an ideal bias improvement in general as a rule of thumb. For the rears you need to look for a 2000-04 Legacy with rear discs in the salvage yard. You need to get the loaded calipers with brackets and rotors.

So adding the rears alone and maintaining equal pad material front and rear would be a solution in itself. And as you can see by upgrading to any of the oem fronts would not only negate that inherent rear improvement but further front bias an already front-biased chassis, decreasing braking performanc of the car.

So you have to get a plan together before upgrading the fronts. The only advantage to increasing front rotor size is in increasing heat capacity or fade resistance. While thats a good thing, its unlikely youre fading your brakes at all or rarely at best and giving up braking performance IMO is not worth increasing rarely necessary heat capacity.

Legacy777 had the same stock setup as yours and had to go to the great length of swapping master cylinder and proportioning valve to get a near stock bias condition using WRX fronts and B4/GT-B rears(same torque output as "H6".)

You can dial some additional rear brake torque in to counter a front upgrade by using a higher coefficient of friction rear pad, but you would need to research both front and rear pad coefficients.

Hope that all makes sense.

ss

[bpimm]

Originally Posted by subysouth

Lemme try to explain the larger picture. You need to maintain stock bias or somewhat increase rear torque compared to the fronts to improve braking performance. There are two sources for brake torque from the braking system, one fixed or inherent and the other variable. The above stats are for inherent or fixed changes based on increasing piston area and/or effective disc radius. The variable component is pad coefficient of friction.


The inherent torque increase of going with the "H6"(short term for the 2000-04 Legacy rear setup using the 290x10mm rotors) rear versus your stock rear setup would be ~+10%. And adding 10% to the rear torque is about an ideal bias improvement in general as a rule of thumb. For the rears you need to look for a 2000-04 Legacy with rear discs in the salvage yard. You need to get the loaded calipers with brackets and rotors.

So adding the rears alone and maintaining equal pad material front and rear would be a solution in itself. And as you can see by upgrading to any of the oem fronts would not only negate that inherent rear improvement but further front bias an already front-biased chassis, decreasing braking performanc of the car.

So you have to get a plan together before upgrading the fronts. The only advantage to increasing front rotor size is in increasing heat capacity or fade resistance. While thats a good thing, its unlikely youre fading your brakes at all or rarely at best and giving up braking performance IMO is not worth increasing rarely necessary heat capacity.

Legacy777 had the same stock setup as yours and had to go to the great length of swapping master cylinder and proportioning valve to get a near stock bias condition using WRX fronts and B4/GT-B rears(same torque output as "H6".)

You can dial some additional rear brake torque in to counter a front upgrade by using a higher coefficient of friction rear pad, but you would need to research both front and rear pad coefficients.

Hope that all makes sense.

ss

Yes, it sounds like the H6 rears would be the way to go if brake performance was the only issue, however dropping 1000 feet in elevation in about a mile of twisty road (Fun Road) every time I leave home I do have a tendency to heat and fade the brakes. the first time I pushed it down the hill I only made it halfway before noticing the brakes fading. The last 1/4 mile of the hill is a 20% grade with a stop at the bottom.

So my main reason for the upgrade is to get the heat capacity and fade resistance up as much as possible. and granted the increase in the rears would lighten the load on the fronts, but I don't think it would be enough by itself. so my plan is to get the biggest brakes possible on the front for heat dissipation and then work on the rears to get them up to match the fronts. Swapping master cylinders and proportioning valve is a possibility.

Maybe Legacy777 can give me a rundown of what he had to do. Please.

Thanks

Brian

[plasticguy]

get the whole wrx front set-up, change your brake lines, flush out all the old brake fluid (from all four calipers and lines and ABS accumulator according to the factory procedure) and switch it over to a good DOT4 fluid, and you are all set

you won't have completely stock brake bias, but you'll be fine. If you want to upgrade your rear pads, now would be the time.

[Huffer]

Originally Posted by Jonathan

Has anyone done a Legacy drum to RS/WRX Rear disc swap ?

I did a drum to 1pot conversion on my Impreza (ok, I organized the parts and had someone else do it). I was swapping out suspension at the same time so it was easy/easier.

My braking, even on stock pads and rotors, was so much better. When I hit the whoa pedal, it didn't feel like the rear of the car was going to pile into me.

The new suspension helped reduce nosedive too...

[subysouth]

Originally Posted by bpimm

Yes, it sounds like the H6 rears would be the way to go if brake performance was the only issue, however dropping 1000 feet in elevation in about a mile of twisty road (Fun Road) every time I leave home I do have a tendency to heat and fade the brakes. the first time I pushed it down the hill I only made it halfway before noticing the brakes fading. The last 1/4 mile of the hill is a 20% grade with a stop at the bottom.

So my main reason for the upgrade is to get the heat capacity and fade resistance up as much as possible. and granted the increase in the rears would lighten the load on the fronts, but I don't think it would be enough by itself. so my plan is to get the biggest brakes possible on the front for heat dissipation and then work on the rears to get them up to match the fronts. Swapping master cylinders and proportioning valve is a possibility.

Maybe Legacy777 can give me a rundown of what he had to do. Please.

Thanks

Brian

It is viable if you want to invest the additional money and time.

And on a side note, brake fade can be entierly eliminated on your stock rotors with pad and fluid upgrades.

ss

[subysouth]

Originally Posted by plasticguy

get the whole wrx front set-up, change your brake lines, flush out all the old brake fluid (from all four calipers and lines and ABS accumulator according to the factory procedure) and switch it over to a good DOT4 fluid, and you are all set

you won't have completely stock brake bias, but you'll be fine. If you want to upgrade your rear pads, now would be the time.

Youre advising someone to setup an unsafe braking situation on their car.

ss

[GuamSTI]

I hope somebody will still read this thread. I have a 98' LGT and the problem is that (1) slipe pin bolt broke and I could not remove the piece that is left inside the caliper bracket. Is this part interchangeable with the single piston legacy front disk brakes? How about the slide pins? There is no other 98 LGT on Guam most common are the "L" Wagons.