wrx brake swap master cylinder?

[206er]

can you retain the stock master cylinder when swapping to 11.4" brakes on a 91 L wagon? and does it matter witch car the brakes came from, i. e. wrx wagon vs. sedan? if only the fronts are used, will the difference in bias be noticable, and if the rears are also used is the legacy master cylinder adequate? Im about to undergo this swap as I need complete new front brakes. currently in the process of sourcing the calipers, carriers, and rotors. should I use new lines with the swap or are the old ones ok? Im also planning on using dot 5 fluid, are there any better choices? thanks for any info!

[vrg3]

can you retain the stock master cylinder when swapping to 11.4" brakes on a 91 L wagon?

Yes. If you don't have ABS, though, your master cylinder bore is a little smaller than the WRX's (so the pedal stroke will be a little longer and mechanical advantage will be a little greater). If you have ABS, your master cylinder bore is the same size as the WRX's.

and does it matter witch car the brakes came from, i. e. wrx wagon vs. sedan?

I don't believe so.

if only the fronts are used, will the difference in bias be noticable, and if the rears are also used is the legacy master cylinder adequate?

WRX rear brakes are functionally identical to your L wagon's rear brakes, so there is no point in swapping them. If you were to swap them for whatever reason, they wouldn't affect anything.

Some people notice the difference in bias and some don't. You should still have overall better braking with the 11.4" front rotors than the stock ones.

should I use new lines with the swap or are the old ones ok?

Inspect the hoses carefully and decide whether to keep them or not. If they're in good condition they'll work fine with the WRX brakes.

WRX hoses will almost fit (the attachment to the strut is a little different). But, you might consider just getting a set of aftermarket stainless-braided lines if you're changing them.

Im also planning on using dot 5 fluid, are there any better choices?

Don't use DOT 5!

First off, the engineers that designed your car say to use DOT 3 or DOT 4.

Second, DOT 5 is not hygroscopic. That means it won't absorb and disperse moisture. Any moisture that finds its way into your brake system will sit there until it rusts through. Also, any pockets of old glycol-based (DOT 3/4) fluid will localize any residual moisture. To avioid that you would have to completely clean all the old fliud out of every part of your car's brake system -- the master cylinder, the hard pipes, the proportioning valve, the hoses, the calipers, ABS if you've got it...

Third, DOT 5 is viscous and it's easy to get small air bubbles trapped in it that won't rise up to the top, so normal brake bleeding won't get rid of the air. This viscosity also can destroy ABS systems.

Fourth, DOT 5 doesn't have the same lubricating properties as DOT 3/4. Our brake hydraulics were designed with the expectation that the fluid flowing through them would lubricate them.

Sorry for the novel... just wanted to give explicit reasons instead of just saying, "you shouldn't do that." Just get some good DOT 3 or DOT 4 fluid. You could probably use DOT 5.1 (I don't know so much about that), but I doubt it's worth the expense unless you're racing your wagon.

[Legacy777]

vrg3 answered a lot of your questions.

I have done the wrx front swap, and have pretty much swapped every other stock component out for different ones to tweak the braking system and how the bias is setup.

My suggestion is do the swap, see how things are and then go from there.

If you feel your pedal travel is too long, and you don't have abs, you're only option is a 1 1/16" bore MC from the non-abs SVX. There are none left in the country from subaru, so you'll have to find a reman one or used one. I'd recommend a reman. That's what I'm using.

[ciper]

I swapped to WRX rear brakes. Not because they are better in any way but they where newer than the units I had and came very cheap. I say get the WRX fronts.

[vrg3]

WRX rear brakes do have a larger piston than BC non-turbos. BC turbos and BFs have the larger rear caliper pistons. So for some board members WRX rear brakes are an (admittedly minor) upgrade. Just not for 206er since he has a wagon.

[206er]

wow, thanks for the great replies. my wagon does have abs so Im set there.the guy I am possibly buying from is wanting to sell the brakes as a complete set so even if the rears are no different Ill get them as spares.
vrg3, thanks for the info on dot5, I was told it deals with heat better but my wagon will never see the track(well maybe someday) so Ill go for the regular dot3/4. also looking into ss lines, who has em, what kind, what price? they seem like a good idea for longevity's sake plus they look cool!

[vrg3]

vrg3, thanks for the info on dot5, I was told it deals with heat better but my wagon will never see the track(well maybe someday) so Ill go for the regular dot3/4.

It is true that DOT 5 generally has a higher boiling point than DOT 3, but it all depends on the specific formulation of fluid. Also realize that if any moisture gets in (and it does eventually), DOT 3/4's boiling point falls but is still relatively high, but DOT 5 won't absorb the water so the water will boil easily.

also looking into ss lines, who has em, what kind, what price? they seem like a good idea for longevity's sake plus they look cool!

They also improve pedal feel because they flex less.

I have Goodridge ones on my car (at the time I bought them I believe they were the only DOT-certified ones for our car), which I got for around $90 plus shipping from MPJ Performance. I'm very happy with them. They came with everything needed, including new banjo bolts and copper washers and clips to secure the lines to the struts. It looks like Z-1 Performance has them for $95 shipped:

http://www.z1auto.com/prodmore.asp?mode ... prodid=558

I think Brat4by4 is running some inexpensive ones from eBay:

http://cgi.ebay.com/ebaymotors/ws/eBayI ... 2454931581

A lot of brake lines out there aren't DOT-certified. That doesn't necessarily mean they wouldn't meet the certification requirements, though. It's just often manufacturers don't have the time and resources to go through the certification process.

The lines are the same for our cars as for GC-chassis Imprezas, so you might want to look through the Classifieds on NASIOC.

When you do install new lines, be sure to use new copper gaskets on the brake lines, and replace the banjo bolts if they don't look excellent on the threaded portion. And be sure the lines aren't twisted at all and don't rub on anything (stainless steel braiding will quickly cut through almost anything else if they touch and vibrate).

[THAWA]

I thought we couldn't use the brake lines that were two ifferent lengths, or is that just the picture?

[vrg3]

That picture is just a generic one they use in all their auctions.

http://bbs.legacycentral.org/viewtopic.php?t=1698

[THAWA]

gotcha

[Legacy777]

other thing I will throw into the mix. There is actually DOT 5.1 brake fluid which IS compatible with DOT 3 & 4, and has slightly higher boiling points. It however it does absorb water faster and needs to be changed out more frequently.