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If you're like me, you hate a vague and squishy brake pedal! The RX's pedal can be a little hard to modulate sometimes due to the characteristics of the master cylinder. It is tuned for an easy-feel and comfort vs. a more driver-oriented firm and immediate response. A lot of RX owners might enjoy this, but I wanted a sportier feel! I ended up going to a 10" brake booster vs. the original 10.5" and a bunch of other changes, but this post should get you 90% of the way there for a lot less money and work!
Here we have two master cylinders, both 7/8" bore, 1.57" stroke length and with two M10 fluid ports facing the passenger side. One made by Aisin (RX - bottom) and one by Advics (IS350/GS35 - top). They look similar, right? Well, they couldn't be more different! Let's take a look:
RX - The spring has more coils and is noticeably softer! You are not met with resistance until you push the piston in deep. This is how the RX's master cylinder feels! Very dead near the top, but it engages in a panic/hard brake scenario! Effective, but a little vague-feeling.
IS350/GS350 - This spring is thicker and has fewer coils! There is immediate resistance and heft when you try to push the piston in, this provides an immediate and solid brake feel! There is more feedback and it is noticeable when you get to the end of the stroke - no sponginess!
Pull the piston out and there is instantly something apparent! They are the same length, but the RX one (left) has far more holes than the IS/GS one (right)! Similarly to the power steering pump, the RX one allows more volume for a softer feel in the master cylinder!
I hope that gave you a better understanding about master cylinders are why our RX's pedal feels a little soft! It is intentional by design, although still effective, I wanted something a little "spicier"! Switching to the IS/GS master cylinder is a guarantee for a better pedal feel. The 2004-2007 Highlander one is also likely stiffer, I'll take one of those apart next and add it to the post!
^ Watch three different master cylinders get taken apart! Proof that 2004-2007 Highlander uses the exact same master cylinder if you need a replacement and want over-boosted brakes still
01-29-24, 11:30 AM
Easy Brake Feel Upgrade for RX330 & RX350 Owners
