Brake Proportioning-    non disc brakes               BY MELFOL and the RBC

A typical complaint I have heard is that someone’s buggy does not stop fast enough, or the front tires lock up in a panic stop while the rear tires do almost nothing. To understand why this happens, and a simple way to help correct the problem, take a quick look at weight distribution differences between a stock type 1 beetle and a buggy.

First, stock Volkswagen beetles had a good ratio of brake lining to vehicle weight. Carrying this over to a lighter buggy means that staying with stock shoes and drums is usually adequate if they aren’t going to be exposed to water or extreme conditions.

Next, look at the brake cylinder specifications for various years of Type 1 Volkswagen.
--Prior to mid 1958 VW used 19mm front wheel cylinders and 17.5mm rear wheel cylinders.
--After mid 1958 VW changed to 22mm front cylinders and 19mm rear cylinders.
--In 1968 rear brake linings were widened a little and the rear wheel cylinders were changed back to 17.5mm. The fronts remained 22mm.
Note: Other things being equal, the larger the cylinder the greater the braking power of that cylinder.

The above specifications are for the weight distribution of a stock VW beetle. Traditionally when brakes are applied the inertial weight in the front of the car squashes down on the front wheels and most of the stopping ability happens up front, typically over two thirds of the braking. Note that larger cylinders are used on the front even though the front of a stock beetle is lighter than the rear. Now consider that turning a VW pan into a buggy greatly changes the stock weight distribution. On a buggy the front is drastically lightened, more of the weight remains in the rear, and a shortened pan diminishes the amount of inertial leverage that can be applied to the front wheels under braking. To this we add the fact that larger tires are often put on the rear. Changing the weight distribution and tires without changing the stock braking proportion front to rear is what causes buggy front wheels to lock up much earlier than the rears. In fact, it is almost impossible to make some buggy rear wheels lock up on pavement when using stock VW wheel cylinder placement. Not only does this combination make the braking very poor, it can be dangerous. Stopping distance is greatly increased. And when the front wheels lock up you loose the ability to steer. Loss of steering can be a real problem when descending a steep hill in the dirt, or braking coming into a corner in sand.

To remedy this problem you can go for a proportioning valve, and perhaps disk brakes. But there is a fairly simple way to alter a buggies braking proportion using inexpensive over-the-counter VW parts. I have done this to my buggies, and, though not perfect, it provides greatly increased stopping power and better handling while braking.

The trick is to shift more braking into the rear wheels and less into the front. The basic modification is to switch front brake cylinders to rear, and rear to front. Which combination of front and rear cylinder works best depends on the size of your tires and the weight distribution of your buggy. At times choices are limited because only one other size cylinder may exist for the year model of your brakes. Usually a straight switch, front to rear, and rear to front, makes a great improvement. (You can also play with lining sizes, changing backing plates, etc., allowing for more options, but for this article we are concentrating on wheel cylinder switch.)

At times backing plates and brakes have been upgraded to newer than the year of the pan. You may have front brakes from early 1958 and rears from a 1969 Type 3 or any other combination. Walk in a parts house and the first thing they want to know is the year and model of the vehicle. Often one doesn’t know what year brake parts they have on a buggy. I have found it best to remove a front and rear cylinder from one side of the car and visit a helpful VW parts house to try to determine which wheel cylinders to use for the switch. New cylinders are inexpensive so I prefer to upgrade rather than try to switch used cylinders. Basically, you want to replace the large front cylinder with a smaller one having the same depth dimension from backing plate to center of shoe. Then try to find a large (front) wheel cylinder that matches the dimension from the rear backing plate to the center of the rear shoe.

Hold the mounting surfaces alongside each other and compare. Do not go by the location of the round portion having the bleeder screw as this is not the mounting surface. You must compare using the tang where the cylinder actually bolts to the backing plate. Sometimes the differences are hard to spot. If you get the wrong wheel cylinder the brake shoe will be at an angle and not seat flush with the inside of the brake drum. If the distance is too great the same wrong angle applies plus a rotating brake drum can scrape against the shoe or tear the protective rubber cup that keeps dirt away from the piston.

Often the 1968 and later 17mm rear will fit the front on most buggies. The rears can be a little more complex for swing axle, sometimes needing a backing plate change to 1968 and later if you want to go to 22mm cylinders. But even if you can’t make the backing plate swap changing to 17mm front cylinders will be an improvement. My experience is 17mm fronts and 22mm rear cylinders are a nice combination for my buggies.

Your life rides on the ability of your brakes to control the buggy. Best to not compromise. Test and re-test to make sure the brakes are working right. Have a working emergency brake. Don’t risk doing it wrong. There is too much riding on your brakes.

(with due acknowledgement for the input by jsturtlebuggy!)
mel
Institute of Fiberglass Narcosis, Mentone Beach, Calif.