Brake Sensors

parid · Post by **parid** » Mon Jan 07, 2013 10:02 pm

Two data points I'm dying to get are brake pressure (what kind of input are we getting from the driver), deceleration (how much energy are we dissipating), and brake temp (how effectively are we shedding that energy that we turned into heat).

Decel should be easy with the built in sensors.

Brake pressure seems to have reasonable commercial sensors available. How are they installed? Since it deals with brake hydraulics I'm super paranoid about safety. This has to be installed right the first time. No thread mismatches here. Is anyone doing this currently? Any tips?

Brake temperature seems more difficult. What are other people doing? Any tips?

GameboyRMH · Post by **GameboyRMH** » Mon Jan 07, 2013 11:24 pm

There's nothing special about brake pressure sensor installation, it just has to be done right, you may need two depending on your brake system. Wilwood makes a unit that distributes pressure to all four wheels, gives you adjustable bias and has a port for a pressure sensor.

It might make more sense to capture analog brake pedal position.

For temperature, if you want to get brake fluid temperature you can put a temp sensor in the reservoir that will stand up to the brake fluid, but if that's not your goal it would make more sense to get the brake disc temp. That's part of an idea I'm working on but I haven't found an infrared thermometer sensor with a temperature range practical for a brake disc yet.

freds4hb · Post by **freds4hb** » Thu Jan 10, 2013 7:38 pm

Quick note, to get the most out of brake pedal info you'll want to capture both brake pedal distance and brake fluid line pressure.

Here's a brake fluid line pressure sensor example (it's the Bosch units from the E39 sourced via ebay)
http://www.ebay.com/itm/160878847017?it ... 60&vxp=mtr

so sensors can be had for reasonable prices. (not the big bosch #'s on their main site) hunt around.

combining data from the pressure and foot travel will give you the most brake data and Race Capture Pro is designed with that in mind.

dimondjack · Post by **dimondjack** » Tue Jan 15, 2013 1:45 pm

You may want brake pressure on each circuit if you have independent front/rear circuits. You can use wheel speeds in addition to pressures to determine at what force your wheels are locking, something that can help tune your brakes.

You can get brake rotor temp with an IR sensor, although you need to make sure it is one that does ok with a shiny surface. What would brake fluid temp show you?

Why is brake pedal travel interesting? It seems that pressure will give you the exact braking force applied.

cng1 · Post by **cng1** » Tue Jan 15, 2013 11:47 pm

dimondjack wrote:Why is brake pedal travel interesting? It seems that pressure will give you the exact braking force applied.

As you say line pressure is the only thing of interest. Given line pressure the position of the pedal is entirely redundant and in general the trace will be so noisy that even if you have it you'll immediately turn it off so you can get a better look at everything else!

Post by **brentp** » Sat Jan 19, 2013 10:49 pm

IMO Comparing pressure and travel would only be useful to diagnose problems with the brake system (leaks, air in the system, fluid boiling in the caliper).

For just understanding vehicle dynamics, hydraulic pressure is the primary thing to look at.

Now: I want to see the datasheet for that BOSCH sensor!

cagedruss · Post by **cagedruss** » Sat May 25, 2013 9:03 pm

Wouldn't brake pedal travel also show potential pad wear also? That is really important in long races.

GameboyRMH · Post by **GameboyRMH** » Sat May 25, 2013 9:22 pm

Not brake pedal travel alone. The relationship between pedal travel and line pressure could help, but it would be hard to tell brake pad wear from brake fluid heat. I think reservoir fluid level would be more useful for that.