Master Cylinder Selection

After using my upgraded brake setup for over 2 years now, I’ve begu to research again and source farther potential upgrades. As I mentioned previously, this particular setup increased pedal travel and I had recommended using a larger brake master cylinder. This is of course if you don’t like how the brakes feel. I’d like to state its not necessary as the stock master cylinder has been tested to work for more then 2 years…especially if you’re working with a tight budget, which most of us are.If have to ask yourself, that type of pedal feel do you want and how do you want the brakes to response. Now with that said here’s what I’ve gathered so far.

I always like to begin with a reference diagram of the original parts (brake master cylinder circled in red):

sxa10stockmr2toyotadiagram

The stock Rav4 brake master cylinder has a inner bore of 7/8″ inches. NOTE – I circled the front brake line outlet as this became a vital sourcing a direct bolt on upgrade.

sxa10mc3 sxa10mc2 sxa10mc1

There are two master cylinder upgraded there are direct bolts on’s…

Subject A

The ST204 1994-1999 Toyota Celica with a bore size of 15/16″ inches.

OEM Part Number # 47201-2B090

st204mc3st204mc2st204mc1

Subject B:

The MCU10 1999-2000 Lexus RX300 with a bore size of 1″ inch.

OEM Part # 47201-48030

rx300mc3rx300mc2rx300mc1

A little general advice about selecting bore size in your master cylinder may be helpful… Decreasing MC bore size will decrease your pedal effort and increase your pedal travel. Conversely, a larger bore in your car’s master cylinder will, all other components being consistent, increase your pedal effort and decrease your pedal travel. As with some other brake parts purchases, this comes down to your preference for how the brakes “feel” under foot when you are driving.

To complete this master cylinder swap, you’ll simply have to use the Rav4 brake fluid reservoir with new seals, bolt it all up, pour some fresh fluid and bleed the brakes.