Brake position sensor

[TRW407]

The system I have in mind is a CDS CP 2000.

Do many folks run brake position sensors (displacement or pressure)?

The logger has lat and long acceleration but I would think a position sensor would be a must?

Thanks for your input.

Tyler Walsh,

[cooleyjb]

The system I have in mind is a CDS CP 2000.

Do many folks run brake position sensors (displacement or pressure)?

The logger has lat and long acceleration but I would think a position sensor would be a must?

Thanks for your input.

Tyler Walsh,

A number of people run a brake sensor. In the last couple years I can't think of a single one I've installed or sold that wasn't using pressure outside of a street car using the on/off indication from an ECU connection.

[ChrisInAtlanta]

Tyler -

My Aim data aquisition system records both front brake pressure and rear, as well as front wheel speed and rear. Both really necessary to optimize your braking - to optimize cylinder sizes, brake compounds, and the like..

A few years back I realized - by looking at the data - that I was dragging the brakes as I drove (autocross). Right foot on go pedal, left foot on stop pedal, outer edges of both feet touching the footwell walls. I was unable to break this habit, so took extreme measures. I rigged a micro switch on the pedal, so if I depressed it enough to activate the brakes, a bright warning light would go on. But I never saw the VERY bright FLASHING LED's. One that was designed for emergency vehicles, labeled "do not look directly into light". . . SO I put it on a stalk, directly in front of my visor, 24 inches away. Yup. I saw that. Nipped that durn habit in the bud.

Well, not EXTREME measures. That would have involved high voltage applied to my. . . well. . . Anyway, that would have broken the habit during the first run.

Chris Eckles
Atlanta

[CDS]

Hi Tyler,

Brake position is not real useful, brake pressure on the other hand can be very useful especially when you do the both front and rear circuit. If you have both brake pressures installed the Co Pilot 2+ automatically calculates brake bias. One very useful application of this is once you have established good bias settings for wet, dry, and damp track conditions, you can dial that bias number in by simply putting your foot on the brake pedal and turning your bias knob while watching the dash. This is done in the pits before going out. It is a real advantage when track conditions change.

We are running a special on brake pressure sensors, 2 for $295. These are 0-1000 lb sensors and work with any system. This is supposed to start with our new Sportscar Ad in the January issue, but seeing as I am posting this, it starts now, Details are at:
http://www.competitiondata.com/specials.htm

[George Main]

The system I have in mind is a CDS CP 2000.

Do many folks run brake position sensors (displacement or pressure)?

The logger has lat and long acceleration but I would think a position sensor would be a must?

Thanks for your input.

Tyler Walsh,

The only difference in terms of brake measurement (as far as performance) between Long G and brake pressure is the determination of when exactly the brake is used.

By that I mean that Long G will "show" braking that isn't braking, but a lift of the throttle and engine "compression" braking (for instance right foot braking and the time it takes to go from throttle to brake). This gap is the major difference that can be seen with a brake pressure sensor. Otherwise, the two signals will be "uniform" in their signature.
It is easy enough to figure out how much of the long g number is engine compression and how much is braking. Usually this is about .3 g's or a bit more for a car with wings or high aero drag.
Once you know this number it's pretty easy to see the brake performance of the driiver without a brake pedal switch, position pot or even a brake pressure sensor.
However adding a brake pressure will absolutely gain you knowledge of the actual brake use and as was pointed out, with front and rear pressure sensors, brake bias calculations and settings are possible.

[CDS]

Decel rate (Long G) with no braking can be quite high and depends on the speed^2 and on the drag of the car. I vaguely remember a magazine article that quoted the decel rate of an F1 car from high speed (with no braking, just throttle lift) as being over 1 G.

The relationship between brake pressure and Long G can be interesting. Set up a math channel dividing brake pressure by Long_G, (with appropriate logic to only consider data when brakes are applied) and you will see that the relationship is not a constant but varies from brake zone to brake zone at most tracks.

[George Main]

Decel rate (Long G) with no braking can be quite high and depends on the speed^2 and on the drag of the car. I vaguely remember a magazine article that quoted the decel rate of an F1 car from high speed (with no braking, just throttle lift) as being over 1 G.

The relationship between brake pressure and Long G can be interesting. Set up a math channel dividing brake pressure by Long_G, (with appropriate logic to only consider data when brakes are applied) and you will see that the relationship is not a constant but varies from brake zone to brake zone at most tracks.

and an atlantic car will see .7-.8 g of aero and mechanical drag with no brakes applied in full downforce trim at 140 mph.

The differences Peter is pointing out would be for instance, in slower corner braking events the max Long G amount "typically" would be less on that sensor yet on a brake pressure sensor, you may see the same pressure as on a high speed braking event. Though the modulation of pedal can be seen in both signals. And to add, uphill and downhill braking events where the Long G sensor is effected by gravity. The brake pressure maybe the same, but the Long G will be different in those braking areas.
With a position sensor on a brake pedal, you would see it's use and measure the distance of pedal travel but if there's any type of change in brake pressure due to heat, air or pad wear you wouldn't be able to account for it. The Long G sensor would see a change in G force and length of the braking area and you could extract information that the problem lies in the brakes where the position sensor wouldn't have the exact same answer WITHOUT an assumption.

Still begs the question that was asked, whether a brake position sensor is better than long G or adding brake pressure sensors. Long G is accurate enough to gain valuable information about braking info (pressure or position) and performance of the driver, as long as there's an understanding and no assumptions of ALL that is being read/displayed by the Long G sensor.

The best scenario is both Long G's (measured) and a front and rear brake pressure sensor
IMHO a brake postion sensor is better used some where else on the car and because the brakes rely on pressure, it's far more important to have that info than the brake pedal position.