Power assist effect of Leading and Trailing brakes.

[theKbStockpiler]

A acquaintance of mine that had 4 wheel discs on a beetle stated that you had to use a lot more force to get his car to stop as apposed to his stock drum set up. So my question is ,does the single leading shoe on a beetle offer more power assist than a disc set up?

Thanks!

[trbugman]

I can tell you that switching to disks on the rear of my Ghia, disks in the front stock, reduced the amount of force required to stop and made stopping in the rain much more controllable. Worth every penny to me and as a bonus no adjustment needed to keep the brakes working great all the time.

[Ol'fogasaurus]

theKbStockpiler you might need to change MC to get proper brake piston size (the piston smaller that drum brakes), bias and chambers. VW, as I remember, is setup to have the front brakes start to engage a bit sooner than the rear (this is in the MC) and early VWs used only a single piston MC instead of the later dual chamber MC required by the DOT for cars made after a certain time period.

Another option might be to add an adjustable bias valve to get this proper brake bias. Stock bias is more towards the front brakes (which means they start to engage first but with double discs you might need to get the braking changed to get the rear brakes to engage sooner.

For what it is worth

[Jadewombat]

I assume you mean el cheapo EMPI disk brakes or something like it. As Ol' said, brake bias is also key to getting correct and pedal feel. My setup felt as solid as a Mercedes pedal feel.

http://www.shoptalkforums.com/viewtopic ... 1&t=139683

[Bruce2]

A acquaintance of mine that had 4 wheel discs on a beetle stated that you had to use a lot more force to get his car to stop as apposed to his stock drum set up.

My bet is that he installed a large diameter Bus MC. The large MC causes higher pedal effort.

VW, ..., is setup to have the front brakes start to engage a bit sooner than the rear

There's no time delay. Both ccts react at exactly the same time. One difference is that front brakes are more powerful than rears. That may give an impression of acting first.

[theKbStockpiler]

Thanks for the replies!

Would type3 rears have more assist than stock drums or discs?

[Bruce2]

What's "more assist"?

Type 3 drums are larger in diameter and wider than late Type 1 rear brakes. They also use a larger diameter wheel cylinder. All of these make them provide more braking power than Type 1 drums.

Better than discs? I guess it depends on the disc brakes. There are a lot of different size brakes available for Beetles.

[Ol'fogasaurus]

Bruce, it is my understanding that there is a delay... miniscule maybe but it is there. The MC and caliper/slave cylinders are set size wise; by using an adjustable bias valve you do adjust the the timing of their application (over simplified description but it is my understanding that is how it is done) front to rear. You can also set the balance by changing cylinders and, if needed and you don't have them add residual pressure valves.

Lee

[theKbStockpiler]

I have a strong preference to not having to press the brake pedal hard to stop so for just normal driving I want the easiest braking possible.

I have heard of the master cylinder spring setting brake bias from front to rear and vise versa myself.

[raygreenwood]

Brake bias....which is "when" one set of brakes (front or rear on our cars)....starts to kick in....is set in the factory master cylinders by the differences jn spring tension on the the primary and secondary circuit. Typically the pedal pushrod starts compressing the first piston....anx the inner piston does not start moving until the tension on the first circuit spring has increased enough to overcome and start moving the inner circuit piston.

In some brake set ups there is even limiting that goes on as one circuits spring binds up and does not allow as much range of motion or even increases or decreases speed of movement. Its why you have fo be careful just slapping in a, master cylinder that "seems" to be the same size.

You can by an adjustable aftermarket brake bias valve control.....which is not the same as a brake pressure limiter. The brake bias valve controls when a brake set starts to brake. The pressure limiter controls (generally for the rear)....how much brake pressure it receives To prevent lock up On hard braking or wet surfaces. Ray