So today has been a brain damaged day for me, and I've seen conflicting things on this site so I want to check this...
I have a 1993 NA Legacy with ABS. It is my understanding that my brake master cylinder is 1" and that the turbo is 17/16". I'm looking at upgrading my brakes to WRX fronts and '05 LGT rears and want to keep the same (or better!) brake feel by swapping to a larger MC. I found a decent price on a 2003 WRX MC and brake booster and am wondering (a) will this improve things and (b) if this swap would be terribly difficult as I am just getting started with this whole mod the crap out of a Legacy thing
Figure out the piston area of your current calipers and the calipers you want to use. Use these to make ratios with the corresponding MC areas. These hydraulic ratios help to determine the correct MC size to maintain (or alter) your brake feel (pedal effort).
If you find a caliper combo that you want, but not an appropriate stock Subaru MC, check out brake manufacturers for more options.
As far as I understand, because I have the NA car, if I upgrade to the WRX fronts and LGT rears, I will have increased brake pedal travel. I'd really like to use the WRX MC with the single stage booster instead of dual stage, I just want to make sure that it will integrate well with the vehicle.
Yeah that should work and decrease travel. From what I can gather you can use any MC as long as you get a brake booster of the same generation and both cars are abs (or non-abs). There are new boosters and old boosters but I'm not sure when things changed. I think you can use a late 90s impreza L booster with a newer wrx MC.
Another strange thing is that there are only three different MC sizes, but apparently some are different from each other.
You'll be fine with that setup, and the calipers you're looking to use. It's what I have on my car. I wouldn't recommend bothering with the 2003 wrx stuff. It won't work anyway since the brake line ports I believe are in different spots then your legacy.
I have upgraded to the single diaphragm booster, and swapped to a legacy wagon prop valve, but my recommendation would be to just swap the brake calipers, and see how you like things. If you don't like the feel, upgrade to the single diaphragm booster. The only downside to this approach is that you may need to bleed the system again if you can't move the MC out of the way enough to get it out.
"One possible problem that legacy777 and I were talking about is that the fluid demands of the WRX brake systems are over twice that of the standard L system. What is more, the master cylinder is 24.0mm without ABS and 25.4mm with ABS versus 26.99mm on the WRX. I have heard of many, many L/Outback Sport owners driving with a successful WRX brake conversion, but numerically, we are probably at or just beyond the limits of the stock fluid capacity."
Which is why I was thinking that if it were possible to hook up a WRX MC, it would work better. I am getting the calipers, brackets, and rotors from the front of a trashed WRX - the MC, booster, and reservoir are also available for cheap for the swap if it would work.
I can pretty much guarantee to you that all 90-94 Legacy ABS equipped cars have the 1-1/16" (26.99mm) bore MC, which is the same as the WRX. Also, as I mentioned the port location on the MC is NOT in the same spot on the WRX MC as it is on the legacy MC.
