Low Buck 4th Generation (2003-2009) 4Runner Brake Upgrade

The caliper slider is bolted in next.

It’s easy to overlook the retractor spring clips, we did at first until we found them in the box and had to remove the calipers to install them!

The rear brakes are in place!  When bleeding the rear brakes, the 4Runner has a unique auto bleed system.  You don’t need to pump the pedal and open and close the bleeder like normal brakes.  You turn on the power, then hold down the brake pedal and open the bleeder, the ABS pump will automatically purge the line and air in a few seconds of squirting!  The rotors have some play on the lugs and hubs so we had to manually adjust the parking brake, then apply the parking brake to center the rotor, then tighten the wheel lugs.  Failing to do this, the rotor may have some wobble with will make the parking brake make weird clicking and or scraping noises.

With the bigger caliper pistons, we were a little worried that the brake pedal would be longer and mushy but we found that not to be the case.  The pedal feel was still quite good and the brakes were noticeably more powerful.  Although this isn’t an ultra-high performance brake upgrade, it is awesome for off-roading where you don’t want to get a bigger wheel so you can have more sidewall.  It is also a no-brainer to do if you have the classic 4th gen sticking caliper piston problem and need to fix it.  Also anytime you are rebuilding the brake system, why not upgrade!



Rock Auto



  1. I love when you can dig into the manufacturer parts bin and find “OEM+,” style upgrades like these.

    Im on the hunt for a slightly larger master cylinder for my trailblazer ss from within the GM truck family. Factory i think is 1”, and am looking for a 1-1/16th as a baby upgrade, as I’ve found some 1.25” units already.

      1. On a Subaru this is a pretty common upgrade when paired with 4pot non-brembo brakes. Nice pedal feel after it’s done. I think I put in a legacy MC on to my forester FXT? Same with my WRX, I did the same. 1″ to 1-1/16th.

        I’m hoping the mush that is the trailblazer can be firmed up some, without having to go full hydroboost setup… That’s just a complication I don’t want to deal with.

        But thanks for the fair warning,!

  2. Were you able to return the 4th gen calipers to cover the core charges? Or did they not accept them because they are different parts? That’s $330 gone if they don’t accept them.

  3. Is it fair to keep repeating you get “more clamping force” with the bigger pistons? its the same hydraulic force distributed over a larger area. There’s no change at the master that creates said force. Technically it’s the same amount of force over a larger area and therefore less pressure but more evenly distributed over the face of of the pads.

  4. Nice write up.

    Is it just me or is Toyota always underwhelming on their brakes? Tundra brakes in a 3rd gen 4Runner is a solid bump up (which I drive). I am getting a 4th gen V8 and I am happy to see that there is an upgrade that is stock-ish. And yes, P=F/A…so same pressure, greater clamping area for bigger pistons equals greater force. F=PA and all that.

    Toyota needs to bump their brakes up in design. I like stopping.

    1. Japanese companies in general build under braked cars. My theory is that in Japan you cant drive fast for long so there was never a need for killer brakes!

  5. Thank you Mike. This article is very helpful. I have a 4th gen SR5 V6. I believe these rotors are smaller, than the V8 and Sport. Would the backing plate need to be replaced in this upgrade? I appreciate your help.

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