Selecting an Upgraded Master Cylinder for Your Motorcycle

Jul 18, 2022

So you’ve decided to upgrade your master cylinder. Now what?

The information to make a good decision is out there, but it seems that it’s up to you to parse all of the information that you gather from limited product descriptions that have been copy and pasted from the manufacturer’s website, from various rider groups and forums, and your buddy who is quick on the track. Take all that information, swirl it around your head while you try to sleep, make a decision, and pay your hard earned cash. Done deal. Right???

Wait, but did you order the right size? Is your buddy full of shit? Who is “BigDawg2183” on the forum?! Do they really have better information than you did?

We are here to help inform you and make the right decisions.

Brake and clutch master cylinders are fairly simple little machines. They convert mechanical input on the lever into hydraulic pressure. From there, the hydraulic pressure generated acts on the caliper pistons, and in turn that pushes the brake pads closer together, pinching the rotor. I know that is basic, but it sets the base understanding of the system so that we can isolate the master cylinder and it’s effect on the system.

First up is the mounting orientation. With this, there are two main types: Axial Mount, and Radial Mount. Axial master cylinders are mounted parallel to the bar and lever. Radial master cylinders are mounted perpendicular to the bar and lever.

Axial mounted cylinders are generally the original equipment that are installed from the factory. This is due to their low cost to produce. Generally these masters are cast in bulk and offer more forgiving input characteristics than that of radial mounted cylinders. There is generally limited or no adjustability of the lever with the original equipment as they are built to a price point as opposed to a performance benchmark.

Radial mounted cylinders offer greater input and feedback feel through the use of higher quality components, materials, and manufacturing processes. The better feel is achieved by having the lever input act directly on the piston creating the hydraulic pressure in the system. Billet and precision forged cylinder housings, coupled with billet levers can reduce the amount of flex in the system resulting in more direct feel.

Next, master cylinders can come with many different piston diameters. 16mm, 17mm, 18mm, 19mm, etc. What does this actually mean in the real world use? The capacity of the cylinder and size of piston will dictate how much actual fluid is moved. A larger piston is going to move more fluid with the same amount of lever movement. However, there will be a difference in the effort required to move that fluid. So with that in mind, a larger cylinder/piston is not always better. Sometimes ABS pumps can be overwhelmed by the sheer amount of fluid that is being pushed by larger pistons.

As we are discovering, the upgrades that come with new master cylinders are designed to increase customization and result in greater feel. With this, many of the aftermarket master cylinders will allow you to adjust or select the “Lever Ratio” which will change the fulcrum point which can adjust the distribution in braking force with the same input. Simply stated, this will allow you to further customize the bite point and ramp up of the lever feel.

Lever length can sometimes be selected as well. This can be in the shape of a long or short (“shorty”) lever. A long lever will give you a longer throw, meaning it can be more precise, but the lever will need to move further. A short lever will have a shorter throw, but will require more force to move.

At the end of the day, a top tier of master cylinder will allow you to unlock a huge world of customization and allow you to dial in the lever feel and feedback that you want. Every nuance of the system can be customized. Everything from initial bite, to overall lever throw can be adjusted. As everything is a compromise, when you open up more adjustment points, finer balances can be struck.

Do your research to see what brake and clutch master cylinder is right for your motorcycle. If you have questions about what is right for your setup, reach out to the team here at Motovation USA.