nvmylh wrote:Hey Jezza I have been looking into my potential brembo brake install, can you confirm what model booster and master cylinder you run? GDB WRX STI? Was it a bolt on job? Cheers
No worries! You will have to change the brake booster if you are planning on running the 1 1/16" master cylinder- these master cylinders will not bolt onto the Lib brake booster! From what I was able to work out all the Subaru brake boosters share the same firewall mounting hole spacing; where they differ will be in the length of the brake booster input shaft, and the mounting pattern of the master cylinder. IIRC the 1 1/16" master cylinders were available in the WRX STi up until 2007, so any WRX brake booster up to 2007 will bolt onto the Liberty firewall and will allow you to bolt the bigger master cylinder to it.
The one I got for mine is from an 06 GDB WRX STi- part number F01G061021. These have the benefit of being 'tuned' for brembos- whether or not this makes much of difference though I have no idea. I chose this one as I got it used for a good price- I paid about $80 for it which was comparable to a non-brembo brake booster at the time. This fit in my car (sedan) with zero modifications to the booster itself; however in a friends car (wagon) the welded seams of the booster interfered ever so slightly with the brake lines running behind it. This was easy to fix by rolling over the welded seams with a hammer- which had no detrimental effect to the booster.
The clevis where the brake booster input shaft connects to the brake pedal does need some modification. The input shaft on the WRX boosters is slightly longer- if you connect it directly to the brake pedal of the Liberty it will lock-up the brakes the first time you use them- and not release them again. This is easy to fix by drilling a new mounting hole in the clevis 10mm below the existing one. I also ended up trimming about 8mm off the threaded section of the input rod- but make sure you measure this on your car as this measurement depends on where you drill the new hole! This allowed me to adjust the pedal position where the brakes start to grab to be only a few mm into its travel, leading to an immediate braking effect that is very confidence inspiring.
New hole drilling in booster input shaft clevis
New mounting location of clevis pin versus old
The master cylinder I bought brand new. My entire reason for the upgrade was a suspected master cylinder failure, and I didn't want to mess around with a used part that is safety critical. I ended up purchasing a Protex master cylinder- part number 210A0076. This has the 1 1/16" (26.98mm) inner bore, and uses M10x1.0 double flare fittings. If your car does not have VSC congratulations- it will bolt onto the new brake booster and you can use your existing brake lines! Even the electrical connector for the brake fluid level sensor is the same.
If you have a VSC-equipped car, however, bad luck as you are not done yet. The VSC master cylinder uses M12x1.0 fittings and the ports are in different locations to the non-vsc cars. There is no 1 1/16" master cylinder fitted to vsc-equipped Subarus. As far as I can tell the VSC system uses these larger fittings as the pressure pulses when VSC activates are large, and the M12 fittings ensure they are not a bottleneck. In saying that, I have now had the new master cylinder fitted for many vsc-activating moments and had zero issues. You will require custom brake lines with M12x1.0 fittings for the ABS pump side, and M10x1.0 fittings for the master cylinder. I ended up getting some thick wire, bending it into shape with the new master cylinder installed and took that to the local brake shop to get the custom lines made, which cost me $30 for the two lines. I got these lines made up with 1/4" steel brake lines, which is the stock VSC size, to ensure minimal resistance to spikes in fluid flow.
Custom hard lines (mock up) required for VSC-equipped vehicles
It is definitely worth bench bleeding the master cylinder before installing it. If you buy it brand new there is no reason to not compress the piston the whole way, and it should only take 15-20 pumps of the piston to get the air out. if it takes longer than this you may have a DOA master cylinder- we experienced this doing this swap on Leon's (turbolag's) wagon. After attaching the lines I then bled them, leaving them only loosely connected to the ABS pump. This helps reduce the amount of air you get in the ABS pump, and makes bleeding that a lot easier. Be very very very careful with the fittings going into the aluminium ABS pump- the first lot of custom lines I got had a bubble flare, not a double flare. When I went to tighten the fitting it just stripped out the ABS pump
. Be very careful and double check the fitting style you get on the brake lines before installing them!
Cheap bench bleeding setup- less than $20 from Supercheap!
Even with this issue though I still 100% recommend this if you are tying to get more out of your brakes! Knowing what I know now I would even do this before fitting brembos- the brake feel you get with the larger master cylinder is phenomenal and very confidence inspiring. Coupled with some good brake pads (I have been currently trying Forza FP3's with very promising results) this is a fantastic and underrated mod for these cars.
I had to swap over the VSC computer from my ABS pump when I stripped the thread. The replacement pump I got was from an automatic, which features the same pump and electronics, but with different VSC tuning. I ended up swapping the electronics module from my car as it was undamaged, and I was not able to find a VSC-equipped abs module from a manual! I thought the internal structure was very interesting and something many people may not have seen.