Beefing up your rear brakes on a VW based trike.
If you are using a swing axle trans. (Up to 67) First you must replace the swing axle backing plates with 68 or later ones, so you can install the 57-on 22mm front wheel cylinder or the Super Beetle front 23.8mm.
Depending on year and model of your backing plates you MIGHT have to slot/enlarge the mounting bolt hole for the wheel cylinder. I have used a chain saw file from the hardware store to do this.
Also most front brake wheel cylinders that are installed on the rear are upside down. As in the bleeder nipple is on the low side and the brake line above. It can make it difficult to bleed, but it works.
On the rear of a IRS trans just install the bigger front wheel cylinders and slot the hole as needed. An advantage of the 68-on IRS rear brakes is that the brake shoes are about 1 5/8" wide compared to the 1 3/16" wide shoes used on the swing axle set up.
You also want to get upgraded brake shoes. Something semi metallic and good quality.
Along the lines of aircooled.net's "super stoppers". You used to be able to get the better shoes at your local parts store. But lots of this outdated stuff is getting harder to find.
One step better then the std. IRS rear brakes would be installing the Type-3 rear brakes (65 & earlier for 5-lug drums) Type-3 linings are wider ( 1-3/4") and the drums are larger in diameter and they already have the 22mm cylinders. Or you can use the 23.8mm front super beetle wheel cylinders with the T3 rear brakes. You will have to remove about .550" off the outside snout of the drum to use them with the swing axle short spline transmission. If you get the complete set up, backing plate, drums and all, it's an easy bolt on installation. 5-lug axle splines are 1 7/8" & 4-lug axle splines are 2 1/2" long Now there are other set ups that can be made to work, like some type-2 "Bus" and 181 "Thing" brakes, but they are hard to find and the price can be high.
Because disc brake kits have steadily gone down in price they would probably be cheaper than the Bus or Thing brakes. And disc brakes on the rear is by far the best brake set up as far as fade and upkeep.
To get better pedal you might want to install a 2-psi residual pressure valve in the disc brake line. Or a 10 psi if using drum brakes. Install the residual valve as close to the master cylinder as possible if it does not screw directly into the master cylinder. If your Master cylinder is lower than the brake calipers then you will need the residual pressure valve for sure.
Master cylinders work just the opposite as wheel cylinders. As the MC diameter gets smaller less pedal pressure is required but the longer the movement. The larger the master cylinder bore, the more pedal pressure, (but less throw), is required for the same braking.
The most common master cylinder used is the aftermarket 3/4 inch (19mm). If every thing is set up correct, there is plenty of fluid to do the job. But if the rotors are not true or the drum brakes are out of adjustment you might be lacking on the amount of fluid the 19mm bore master cylinder will push. The buggy 22mm master is very common but may require more pedal pressure than desired.
There are other master cylinders offered with bore diameters, 5/8" to 1", that you can use to adjust pedal throw and/or pressure.
Make sure the pedal comes all the way back after every time the brakes are applied. The brake rod must have a small amount of free play when the pedal is all the way back.
Make sure your pedal ratio is somewhere around 7 to 1. Pivot point to foot vs pivot to cylinder. You must have this mechanical advantage as it dramatically effects pedal pressure needed.
Use Dot-3 fluid and flush the system every two years. Hot & cold, sun and shade and part time use has a tendency to produce moisture in the brake lines much faster than if the lines are under a daily use car. Flush the brake lines with brake fluid, dry air or alcohol. One drop of oil in the fluid will contaminate the fluid.
Never get oil on the linings and forget the "brake clean" as it just dissolves the oil and lets it go deeper into the lining. Race mechanics won't let you touch the lining as even the oil off your hands is not wanted.