Brake specspiston diameter specs of 36/44, want to know what that means???
08-17-2005, 12:41 PM
#1
Rennlist Member
Thread Starter
Brake specspiston diameter specs of 36/44, want to know what that means???
read below, but NOT my post. I was provided erroneous information. I would delete the string but I don't have the access to do so!
Last edited by Martin S.; 08-17-2005 at 07:00 PM. Reason: Bad Information: Do not read this thread.
08-17-2005, 01:55 PM
#2
Weathergirl
Rennlist Member
Rennlist Member
Originally Posted by Martin S.
Our multipiston calipers are designed such that the larger pistons are on the leading edge and the smaller on the trailing edge.
You're right though--that's what Smith wrote in Engineer to Win. Strange that he would get it wrong, but back in the early '80s when he wrote it, there weren't many differential bore calipers around.
08-17-2005, 02:08 PM
#3
I don't have Smiths book, it is supposed to be good, but....
smaller leads because there is a layer of very hot(yes, hotter than the front) gas and debris that build up after the leading piston. the larger piston in the trailing position exerts a greater force and will theoretically push through this plasma like layer.
W/o differntial bores in the calipers pads will exhibit taper wear, The 930 4 piston and older S, A and M calipers used stepped bores oriented in such a fashion that the pad was cocked on them in order to avoid or at least reduce taper wear.
there is more to brake bias than just the bore sizes, things like rotor diameter, p/v, ABS characteristics and coefficient of friction also are influences.
smaller leads because there is a layer of very hot(yes, hotter than the front) gas and debris that build up after the leading piston. the larger piston in the trailing position exerts a greater force and will theoretically push through this plasma like layer.
W/o differntial bores in the calipers pads will exhibit taper wear, The 930 4 piston and older S, A and M calipers used stepped bores oriented in such a fashion that the pad was cocked on them in order to avoid or at least reduce taper wear.
there is more to brake bias than just the bore sizes, things like rotor diameter, p/v, ABS characteristics and coefficient of friction also are influences.
08-17-2005, 02:38 PM
#4
Taper wear of the brake pads is basically caused by the simple fact that the trailing edge of the pad runs hotter than the leading edge and so wears faster
If the leading edge of a four pot piston (That's what we have) are made largerthan the trailing pistons (since the line pressure is the same for all four pistons), relatively more force will be applied at the leading edge
W/ the 2 piston designs you worry about the edges, the steps in the piston when at the proper 20 degree angle will orient the pad in such a way as to put more pressure on the hotter trailing edge to push through the plasma like boundry layer.
when they started wanting and making bigger pads they needed 4 pistons to prevent the pad from flexing causing other types of wear and performance issues. The solution to pad flex is 4 pistons, 6 piston and even 8 piston designs w/ mutiple separate smaller pads, these schemes can provide diffferential pressure across minimaly deforming pad structures.
When the 4 pistons first came out they continued to use the step design, but latter figured out that the differential bore solved the problem more elegantly.
In a differential bore caliper you don't worry about the edges so much because hopefully the pad will be stiff enough to avoid deformation that would cause performance issues. But the leading piston has to be smaller than the trailing for the reasons Mr Smith outlined.
Bill: Thanks for the clarification!!!
