How Hydraulic Brake Conversion Works

Mechanic holding tire, preparing to service brake system.
You can convert your brakes yourself, but be prepared for a complex job. See more pictures of brakes.
Sam Jordash/Digital Vision/Getty Images

Chances are you've never thought about your hydraulic brakes being anything else -- unless you're in love with classic cars. When we say classic, though, forget those muscle cars and hotrods and think older. And then go a little older. To find a car without hydraulic brakes, you'll need t­o find a pre-1940s era vehicle -- a real antique.­

When cars were first made, they used just rear brakes. They weren't powerful or heavy enough to require a second set of brakes, and most people thought that braking on the front wheels could cause the car to flip over [source: Joseph]. But generally, by the mid-1920s, cars became more powerful, and the two-wheel braking system wasn't cutting it. Once people realized they wouldn't automatically crash with front-wheel brakes, the four-wheel drum brake system became popular.


Unfortunately, these early four-wheel systems were very complex, with lots of carefully constructed hardware to properly proportion out the force between the front and rear brakes. This system was replaced, but it wasn't until the 1940s that hydraulic brakes became relatively standard on cars [source: Joseph]. Most people now convert their classic cars from mechanical brakes to hydraulic brakes to get better braking efficiency. Don't expect to have the stop-on-a-dime power of a brand new Jag or Mercedes, though. Your revamped braking efficiency still might be only 65 percent [source: Waller].

­Sho­uld you choose to perform a hydraulic brake conversion, the Internet is a great resource for do-it-yourself kits for purchase. Such kits can be simpler no modification kits, all the way up to complex kits that reroute lines and cost several thousand dollars. No matter how you choose to perform a hydraulic brake conversion, be sure to do it thoroughly and carefully -- brakes are probably the most important safety feature on your car!

Read on to find out what tools you'll need to dig out of your garage to begin a hydraulic brake conversion.


Tools for a Hydraulic Brake Conversion




Ready to dust off every tool known to man for your hydraulic brake conversion? Hold up -- you might not necessarily need them.

There are ways to perform hydraulic brake conversions without drills, cutters or an electric welder. Sounds pretty nice, huh? If you buy a no-modification kit, or a kit that uses existing holes within the frame of your classic car, you shouldn't need to drill, cut or weld.

Don't get your hopes up just yet, though. Such kits are expensive and don't exist for all makes and models. An even bigger problem is the fact that you're dealing with a classic car. Your 70-year-old house wouldn't be standing without a lot of maintenance, upkeep and cleaning -- and neither would your classic car. The action of stopping a car that weighs several thousand pounds puts a lot of wear and tear on your braking system, as well as your car. Chances are the existing parts of the brake system that you plan to work with will need modifications as well.

If this is your first time doing any major adjustments on your braking system, be prepared for a lot of dirty work. Even if your car has been restored previously, it might not have been a great job. You'll need to clean and assess your entire system, from the master cylinder to the brake calipers to the type of brake fluid you'll use. If that's the case with your hydraulic brake conversion, you just might need to dust off every tool you've got in your garage.

If you're crossing your fingers that your car's undercarriage is in good condition, meaning all you'll need is a simpler no-mod kit, read on to find out what those kits entail.


Hydraulic Brake Conversion Kits


­I­f you're looking to balance better braking with the desire to keep their car as original as possible, try to find a no-modification kit. Such kits mean you won't have to damage your sweet antique. They use existing holes on the frame, and no cutting, drilling or welding is required. These kits will also often use your original handbrake handle to the rear cable. But for such nice features, be prepared to pay. Your car might stay the same, but your wallet won't -- expect to shell out somewhere between several hundred and several thousand dollars for such a kit. In some cases, you can purchase a complete braking system or just portions of a kit, depending on your specific needs.


A sample do-it-yourself hydraulic brake conversion kit includes:

  • Hydraulic brake assemblies
  • Hydraulic hub drums
  • Hydraulic override coupling
  • Four-hole coupling plate
  • Hydraulic brake flange kit
  • Hydraulic brake fitting kit
  • Motor coil bundy tube
  • Assembly instructions

­[source: Marshall Engineering]­

Because classic car kits are so specific, your best bet for finding one that fits your make and model is probably the Internet. If you can't find one to order online through a simple search engine, try looking at specific forums of classic car clubs for your vehicle. Members have often had similar questions and can direct you to a web site or phone number for a particular garage that specializes in the kit you need.

Since you know front-wheel brakes won't flip your car end-over-end, feel free to start that hydraulic brake conversion anytime! But be prepared -- that even your simple no-mod kit might not keep you from getting dirty or hauling out some tools.


Lots More Information

­Related HowStuffWorks Articles

  • Early V8 Garage. "Specializing in 1932-1938 Ford Hydraulic Brake Conversion Kits." (Accessed 11/19/08)­
  • Endy, Tom. "Hydraulic­ Brakes." Orange County Model A Ford Club. (Accessed 11/26/08)'s%20Special%20Topics/Hydraulic%20Brakes.pdf
  • ­Joseph, Matt. "Collector Car Restoration Bible." Krause Publications. 2005.
  • Marshall Engineering. "D.I.Y. Brake Conversion Kits." (Accessed 11/19/08)
  • Weller, Dave. "Hydraulic Brake Conversion - Brake pedal." Austin Seven Owners Club. (Accessed 11/26/08)