# Hydraulic brake line pressure??

• 05-04-2011
nckeeley
Hydraulic brake line pressure??
Hey all!
I've been searching like mad for any information (including calling tech support for multiple manufacturers) about what kind of pressure that the master cylinders and brake lines on hydraulic brake systems operate at or are designed for. I'd appreciate ANYTHING for ANY make/model if you have the data.

Thanks!
• 05-04-2011
rshalit
not sure what you mean - max. pressure that is applied at lever/master cylinder? Open system is at atmospheric pressure, by definition.
• 05-04-2011
nckeeley
rshalit: Thanks, but I'm really more interested on the closed system...And yes, the max pressure applied at the master cylinder would be exactly what I'm looking for.
• 05-04-2011
frdfandc
The answer is 42. It is always 42.

Or a lot plus 10.

Or eleventy.
• 05-04-2011
the-one1
Quote:

Originally Posted by frdfandc
The answer is 42. It is always 42.

Or a lot plus 10.

Or eleventy.

I think he is looking for a serious answer. Don't throw out random numbers like that. That's not nice. And it's not 42. :nono:

It's "pie are square". :thumbsup:
• 05-04-2011
Moustache rider
The pressure developed will depend on how hard you squeeze the brake lever and will have a huge range.
If you knew what the master cylinder bore was you could figure out line pressure for a given lever squeeze force. However, I have never seen that information published.
• 05-05-2011
The_Rizzle
I'd think max pressure would be mechanical ratio x lever pressure/mc bore area?

So in the hayes stroker trails, - lever mech ratio is approx 5.33:1
The bikeradar brake test went to 150nm, so we can use that.
I think the stroker bore is 10mm, thought I read that somewhere, seems about right, I'll use it.

EDIT: 150x5.33= 799.5
10mm bore = 5mm^2*pi=78.5mm^2

799.5N/78.5mm^2= 10.18MPa, which converts to 1476psi.

I'm not 100% on my math/unit measurements, but this sounds abouts right.

Yeroon
• 05-05-2011
jeffscott
Quote:

Originally Posted by The_Rizzle
I'd think max pressure would be mechanical ratio x lever pressure/mc bore area?

So in the hayes stroker trails, - lever mech ratio is approx 5.33:1
The bikeradar brake test went to 150nm, so we can use that.
I think the stroker bore is 10mm, thought I read that somewhere, seems about right, I'll use it.

EDIT: 150x5.33= 799.5
10mm bore = 5mm^2*pi=78.5mm^2

799.5N/78.5mm^2= 10.18MPa, which converts to 1476psi.

I'm not 100% on my math/unit measurements, but this sounds abouts right.

Yeroon

Math is okay but the unit of force must be Newtons not Newton meters (that is a torque)...

So force X multiplier/area = pressure

If however the input is in Newton meters...then you would have to divide by the lever arm and the area to get pressure.
• 05-05-2011
The_Rizzle
correct - I was thinking they had written Nm, but they were using Newtons.
The 5.33 mech ratio was found measuring a set, and is the farthest you could put a finger on the lever, ala single finger braking.