[6869704x4]

I read a ton of threads on disc brake conversions before I did mine. Both here and at other web sites. One common thing that stands out is guys saying that you move more fluid with disc brakes than drum. I'm not convinced that's true. Can someone explain it?

 

[6869704x4]

I guess if the mods think that this belongs in the noob section they will move it.
Didn't know about the low drag seals, interesting. However, I don't think that the conversions people are doing here involve a caliper that fancy. Do you?
I asked for an explanation because I don't claim to know every little aspect of a braking system.
A lot of the threads I read have people going up in size with their master cylinder thinking they have to move more fluid now that they have disc brakes. I don't think that's true. I think as a general rule you move less fluid(once the system is filled and bled) with disc than drum. Since that's the case you are now looking for more pressure not more flow. Seems whacky but to get more pressure you need to decrease the master cylinder size. Very few posts I read suggested that. And the ones that did were ignored.
The reason you get more pressure is because of the formula, Pressure=Force/Area.
Just trying to get a decent discussion going and maybe save someone an extra trip to the parts store.

 

[6869704x4]

Good point vintagespeed, so, you are schooled in hydraulics, that will help. I have some hydro schooling too.
The difference, I believe, is in in the travel of the pistons. The caliper piston moves very little, unless you have some serious rotor warpage, in comparison to the drum pistons. I think that is why the typical disc/drum setup has smaller lines to the discs than back to the drums. I only know of two reasons for this. There is not as much fluid movement to the discs, or, there is higher pressure going to them than there is going to the drums. The master cylinder could be doing that but I'm not sure. The ones I have rebuilt had the same size pistons so that wouldnt be the case.