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Chase Bays Dual Piston Brake Booster Delete with Bolt-On 6:1 Pedal Ratio



Forget everything you've heard about manual brakes, forget everything you know about master cylinders and boosters all together. In the last 10 years we have sold over 15,000 Brake Booster Deletes (Single Piston) and have thousands of positive reviews. We've seen it all. Where our Single Booster Delete could be improved upon; it's a single piston design and its working with the stock 3.5:1 to 4.5:1 pedal ratio (depending on the chassis). The pedal ratio is the distance from the top swinging axis to the brake foot pad divided by the distance from the top swinging axis to the master cylinder clevis mounting point.

Changing the pedal ratio to 6:1 is a major function and feel upgrade to allow the use of a larger master cylinder. The OE pedal ratio can only leverage so much, so we’re limited to a 3/4 or smaller master cylinder. The improved Motorsport pedal ratio gives you a better mechanical advantage with additional leverage. This means we can use a larger 1 inch master cylinder with more fluid being pushed per mm of piston movement inside. This is great because it allows you to have a better braking feel and more force to the calipers with equal or lesser force at the pedal. That translates to less leg effort and more braking power while keeping a similar throw distance.

Even after all of our sales and reviews, every single day numerous times a day, we get asked “what are manual brakes like?” and sometimes followed up with “my buddy said they suck!” or "just unplug your vacuum hose!". The FACT is, the fastest road race cars in the world have manual brakes. From F1 to McLaren GT4. The difference in those setups from just slapping a big master cylinder on a plate and calling it a day, is they use pedal boxes with a 6:1 or 7:1 ratio.


A proper manual brake setup (matched ratio with MC bore size, good pad compound, and Front / Rear Bias Adjustment) is the exact same braking every time. The modulation of max braking before lockup is where manual brakes really thrive. The 80-99% zone. Finding the exact level of leg pressure to get that exact threshold is just not possible with power brakes, they’re too inconsistent...especially with boost. Maybe your buddy did X and Y on the track with it but thats anecdotal info. Acquired Motorsport Data isn’t wrong. YES the 80-99% zone is a little more leg effort than power brakes but that’s what makes it so great. This is massively to our benefit in finding the right leg force every time. IF your manual brakes feel like crap, your set up is wrong. And that's okay, we can be reached via and we've seen it all...we can help fix it.

Manual brakes are also great in Drift and Rally environments where nearly every turn has a different entry angle and speed, it’s a far less calculated Motorsport. We’re always making tiny on-the-fly adjustments. If we take the same turn 10 times, we may only hit the foot brake half the time. As well, left foot braking is more common…your left foot isn’t used to braking and is often done on the fly as a correction. With the stiffer slightly more leg pressure 80-99% braking, this allows us some forgiveness in not locking up the front brakes and easier modulation in the opposite foot used to controlled modulation.


Power brakes are inconsistent, especially under boost. When you’re going 100+mph into your braking zone lap after lap…the braking experience MUST be the same. With vacuum assisted brakes we’ve all experienced it…one push is one level of braking and the next is entirely different. This works fine on everyday drivers around town barely paying attention and wanting to put the least amount of effort in. This just simply doesn’t work for most Road Race, Rally, or Drift chassis…which is why under dash manual pedal boxes from companies like Tilton or Wilwood exist.


How can we achieve pedal box function seen in F1, Indy, IMSA, & GT4 without $3,000+ in parts? Without days of prep, relocation of under-dash components, and fabrication? How can we have a DUAL Piston / Isolated Front and Rear Circuits setup thats approved for nearly every sanctioning body from FIA to WRC to Formula Drift plus SAE and DOT approved? How can we achieve this without removing and drilling the stock pedal or without massive modifications to the firewall or interior? Well after years of hard work, testing, and procurement...we’ve got it figured out.


The Chase Bays Dual Piston Brake Booster Delete with Bolt-On 6:1 Pedal Ratio

It will include the following Chase Bays designed components:

• 1” Bore Ultra Compact Master Cylinder
• Isolated F/R Circuit High Heat Polypropylene Fluid Reservoir
• Billet Chase Bays Reservoir Cap with High Heat Vented Diaphragm
• Billet MC / Firewall Adapter Plate with Raised Mounting Point (inside is hollowed for weight reduction)
• L-Banjo Front Outlet Fitting for easy front line mounting w/ SS Banjo Bolt
• SS Rear Outlet Hardline to Adj. Bias Valve
• Adjustable Bias Valve w/ -3AN 90º Outlet
• Carbon 4140 Steel Push Rod and Clevis
• Stainless Steel Bolt-On 6:1 Ratio Pedal Adapter (after measuring dozens of popular chassis, we have 3 different Pedal Ratio Adapters that cater to 90% of the cars you guys drive)

There are about 5% of motorsport builds that require a pedal box. They need to decrease front AND rear pressures simultaneously…if you’re one of them you probably know it! One day soon we’ll make a pedal box for ya.

Beyond this, you will need our Brake Line Kit to make it all work. We make them for the following chassis (click them to be linked to the kit). If we don't make it you will need to make your own lines or have them made. All 3 outlets are -3AN Male.

88-91 Honda Civic/CRX | 90-93 Integra [LHD & RHD]
92-95 Honda Civic | 94-01 Integra [LHD & RHD]
96-00 Honda Civic [LHD & RHD]
Honda S2000 [LHD]

Lexus IS300 | Toyota Altezza | JZX90 | JZX100 [LHD & RHD]
Mazda Miata NA / NB [LHD]

Mazda RX-7 FC [LHD]
Mazda RX-7 FD [LHD & RHD]
Nissan 240sx Silvia S13 S14 S15 [LHD & RHD]
Nissan 350z | G35 [LHD]

Nissan Skyline R32 | R33 [RHD]
02-07 Subaru WRX [LHD]
13-20 Toyota 86 / FR-S / Subaru BRZ [LHD]
Toyota AE86 [LHD]
93-98 Toyota Supra | Soarer | SC300 | SC400 [LHD & RHD]

If you have a BMW, FD RX-7, or Mitsubishi Evo chassis...those get the clutch fluid from the Brake Reservoir. You will need this part to share the reservoir on our Booster Delete: Clutch Feed Adapter for Fluid Feed