Big Brake kit expert thoughts needed

[Bruno]

A floating caliper is like a two piston caliper isn't it?
I think the piston is being pushed against the pad and the body of the caliper is being pushed the opposite side.

So I do think that the fluid displacement on a floating caliper is twice the displacement of a fix caliper piston.

So the area should be multiplied by 2. (or 4 if you take 2 calipers and 8 for the 4 pot calipers.)

If you want to join the Wiki, we can start doing some calculations in there.
http://bmwe34.wetpaint.com/page/Brakes+mods

[Bruno]

this sounds very odd, the hydraulics should take up the extra fluid volume in the system. I understand what you mean about brake pedal travel but calipers shouldn't affect brake height at all. otherwise as the pads wore the pedal would get lower and lower. hydraulic disc brakes are self-adjusting.
I am sure i saw a good section about brake feel in a carol smith book also. might see if i can find the section online.

Sorry I talk about pedal height but it is height when the pedal is depressed.
So it is more of a pedal travel. The pedal height is the same.

I need to get my noise back into the Carol book.

[Bruno]

yeah the 1.75 is probably 1-2 mm per piston bigger than the e31... that is a huge difference in area going from a 1.38 to a 1.75 (x8)...
Area= 'pi' times (radius squared)...

(do calculations in mm for easy comparison to OEM setups and masters.)

1.38= ~36mm (18mm radius)
1.62= just over 41mm (20.5mm radius)
1.75= 44.5mm (22.2mm radius)

The 1.62s would seem to be the perfect size based on piston diameter and fluid requirements.

I would love to know what is the pistons size in the 4 pot front and back setup from UUC... I bought some 1.38 for the back but I think it will be to big now... ARG.

[rob101]

Obviously there is a LOT more motion for these to still permit use of a 42x4 caliper on the same master, which lends credence to the X2 rule quoted above... and they would then fall right in between the 1.38 and the 1.75 in terms of effective displacement winding up about 1413mm2 (damn near a 42x4 4pot caliper.)

Yeah i thought about it last night, and i think i was wrong because the sliding caliper will apply double the force per area of piston because the reaction force of the caliper pressing against the disc will clamp the otherside
http://www.sportcompactcarweb.com/ed...hno/index.html which is confirmed by this article so there you go....

[rob101]

So I do think that the fluid displacement on a floating caliper is twice the displacement of a fix caliper piston.

So the area should be multiplied by 2. (or 4 if you take 2 calipers and 8 for the 4 pot calipers.)

If you want to join the Wiki, we can start doing some calculations in there.
http://bmwe34.wetpaint.com/page/Brakes+mods

I would join it if i wasn't at work right now LOL, first thing that pops to mind bruno is that for pedal feel you should be thinking about pedal travel vs. clamping force. it sounds like atm your thinking in terms of the displacement of the pads/pistons rather than their clamping force, clamping force is what determines the braking torque on a certain disc not the actual caliper piston travel. if you get my meaning.

[attack eagle]

I would love to know what is the pistons size in the 4 pot front and back setup from UUC... I bought some 1.38 for the back but I think it will be to big now... ARG.

jsut reverse engineer the area needed from what is already fitted.

figure the area now, x2 for sliders, divide by number of pistons, divide by pi, square root. piston radius.

Based on the 40mm rear you have now, i come up with a 28mm 4 pot.
that is a 1.1"... so arg indeed.

[Bruno]

Well, time to sell all my 4 pot callipers and pick up the right ones.
No big deal for the rear anyhow, not a priority anymore.

I need to finishe my A-arms to replace the thrust arm and control arms 1st.