Brakes are on my mind lately. My left brake went soft, and I discovered that the pads were toast after only 85 hours, with the right pads being virtually new. For this and a few other reasons, I spent a few days overhauling the brakes and re-bleeding them.
There are a lot of threads talking about some very simple mods that can be done to the brake system. I thought I'd summarize things to look at when working on your brakes, especially for the guys with rudder assemblies that are still easily accessible. I did most of these mods on a finished airplane, thus getting a nice dose of cockpit-diving.
1) The long bolt mod
. Use (4) AN3-56 bolts as the axle of rotation for the rudder pedal instead of using 2 smaller bolts per pedal. Obviously having a single axle of rotation is better than (2) almost the same axles of rotation.
2) Return springs. These help the brakes return to the non-braking position. The mod calls for a spring, stop, and collar on the shaft of each master cylinder. I suspect the left brake was dragging, and I'm hoping this will help improve pad life. It's an easy mod. See pic here
. Part list required is here
3) DOT4 conversion. There are a lot of threads on what fluid to use, including Mil-5606, Mil-83283, Synthetics, Dot4, Dot5, etc. I chose dot4 fluid due to its availability and resistance to fire. If you use dot4, the o-ring mod is required. You also need to use brake lines that are dot4 compatible. The lines that come from Van's are not. Stainless Steel Aeroquip 666 will work. If you're sticking with the MIL stuff, this is not required. I'm not necessarily pushing the dot4 mod. Please go do some research. There are a half-dozen good threads on VAF about brake fluid options. Thanks to Charlie Kuss for being THE source of O-rings to adapt all the brake components to support Dot4. He sent me a complete kit of O-rings with pictures. Replacing the O-rings is very easy.
4) Parking brake valve. I added a parking brake during the build. Frankly, I don't use it much yet. If you think you want a parking brake, do it during the build. Much harder to add later. I used a matco parking brake valve like the ones pictured in this thread
. I'm not sure if this is still available. There are similar looking valves at ACS from Matco and Grove. If you use dot-4, you need o-rings for this too.
5) I also was recommended not to use the default plastic brake lines between the pilot and pax, and that I'd be rewarded with brakes that aren't as susceptible to becoming mushy. The line from the pax to the reservoir would still be the default plastic lines. I haven't done this yet, but maybe next time I service the brakes I'll remember to measure the lines and have the new fittings and hoses at the ready...