could you explain "arc the shoes ""
Thanks Ron
Arcing the shoes will not "improve" your drum brakes, but it is intended to make them work as best as possible when new shoes are installed.
Beetle drums are 9 inches in diameter new, their wear limit is 9.065". Drums are "turned" to remove grooves, ridges and general defects. If they are within wear limits, then they are fit for service.
New shoes are made by laminating or riveting the lining to the shoe. They are made with a lining material that is one consistent thickness. This can make the new shoe's radius over 9". To make the lining contact the drum properly, the shoes can be "arced" to the diameter of the individual drum. A shoe arcing machine is a sander with a jig that holds the shoe firmly in place. You set the machine to radius the shoes to
almost match the diameter of the drums. I say almost because actually you want the new shoes to be radiused to a slightly
smaller diameter than the drums. You want the shoes to contact in the center before the ends contact. A new shoe that is properly radiused and arced to the drum will "rock" when it is placed in the drum by hand. You want the center of the shoe to contact first. The difference is very slight, only .030" or so. The mechanical force of the brakes being applied will force the shoes into the actual diameter of the drum. This was done to ensure that you will have 100% performance from the new shoes right from the start. If not done, the ends of the shoes can contact the drum first, you will have less mechanical advantage, and they may chatter, resonate or make noise on application. And, arcing the shoes is removing some of the lining material, so in theory, it should not increase the life of the linings .
When OSHA (Occupational Health and Safety Administration) stepped in and said Asbestoes dust was unhealthful to breath, that eliminated the arcing of shoes to drums. When you install new shoes nowadays, you can only hope that the radius of the new shoes will be slightly smaller than your drums. If not, they will just have to wear in. You may not have 100% effectiveness right from the start, but they will eventually conform to the diameter of the drum just by wear.
So, at the end of the day you still have 9" brakes on the back of a stock Beetle.
Type III rear drum brakes or rear discs are the way to better brake overall performance IMHO.