JABChev

For a senior design project, we're looking to use a brake caliper from an automotive application to adapt to our system. What i need to know is the maximum pressure capacity of a stock brake caliper, or the maximum clamping force. Knowing one, i can find the other. If this helps, i'm thinking the pressure will be the same (at least for the front brakes) throughout the brake system. So if anyone knows the pressure at the master cylinder that would be a good start also.

1 FMF

iTrader: (1)

normal brake fluid pressure is 1000-1500 psi at the caliper, so i would guess they should be able to handle up to 2000 psi no problem.
I would ask manufacturers of the calipers, or people like wilwood or baer, to get more reliable numbers. It will probably differ for an aluminum versus steel caliper. If I had to guess, I would compare it to a scuba air cylinder for material thickness and strength and those hold from 2200 to 3600 psi of air so a stock caliper might be ok to over 3000 psi.
I would not look for maximum clamping force to base your decision on, because that won't necessarily tell you what the caliper housing can hold before letting go.

wssix99

iTrader: (5)

Pressure multiplied by the total surface areas of the pistons will give you the clamping force. So, to change your force, you can toggle the pressure or the piston surface are of the particular caliper you are using.

mitchntx

iTrader: (14)

Excellent question! ... I'm now curious as well.

I found this ...

http://www.autoanything.com/brakes/61A3154A0A0.aspx

The adaptors would allow you to retrieve real world numbers at about any location and the cost is not a whole lot.

JABChev

Yes i've researched the aftermarket caliper sites for common pressure capacities. The numbers you gave fit right it to what i was finding. I wasnt sure if the stock calipers held the same pressure though. As far as caliper material, i believe most are cast steel with about a 36ksi yield, so as far as the material strength, i would think 3000 psi is very feasable. Also, i believe some calipers have o-rings involved in containing the hydraulic pressures, I would think those o-rings would be a failure mode more common to these units than material strength.
I was thinking if a manufacturer posted the maximum clamping force of the caliper that would give me a rough estimate of the system pressure. However, with safety factors involved, the calipers are propably capable of higher pressures than the hydraulic system in a car can produce.

JABChev

thx, i found one but had a pressure limit of 1500psi, and it costs a little more. lol. we could definately use that during the experiment however, we'll need to know the pressure at the caliper if we choose to use this technique.

johnpate01

iTrader: (3)

Your line pressure is going to be the same everywhere in the system, assuming that you are measuring the front and rear separately and you don't have anything like ABS modules or proportioning valves in the way. Master cylinder pressure from the front output port = front caliper pressure.

That gauge is rated to 3ksi in the description in the link. There is a disclaimer that product may vary next to the picture. Must be a stock photo.

wssix99

iTrader: (5)

Correct. The calipers will handle whatever the hydraulics can give it.

Not surprised clamping force isn't published. In a braking application, the pad size/material impacts performance in addition to clamping force. But - if you know the pressure you are giving the caliper, you can calculate the force with a ruler and 3rd grade math.

mitchntx

iTrader: (14)

I'm not a fluids guy by any stretch, so ...

I would think the pressure would be the same throughout the system, regardless of any ABS module or prop valve.

Those devices alter fluid movement, not pressure, right?

1 FMF

iTrader: (1)

technically they alter both. The goal is to reduce brake fluid pressure going to the caliper, which reduces caliper clamping force and stops the wheel from skidding. In order to reduce brake fluid pressure, you have to remove a small amount of fluid.
there's a few different types of abs modulators, they all work the same way in that they reduce line pressure to the calipers to undo wheel lockup, the differences is in what they do with the fluid. off top of my head one of the big differences are the abs units that handle only rear (drum) brakes versus the units that do 4-wheel abs. i'm sure google on abs modulators would explain it pretty good.

johnpate01

iTrader: (3)

You might also want to look into Race Car Vehicle Dynamics by Milliken and Milliken. They have a great brake section, as do the 6th and 7th editions of the Bosch Automotive Handbook. They are both amazing reference/design aids.

Shaun Sweeney

I plan to run the 4 piston Brembo calipers from a 6th gen V6 Camaro for this reason. I didn't want to increase pedal effort and have no need for a 6 piston. I also prefer 17" wheels on a primarily street driven car and these fit under stock wheels from what I understand.