Brake Bias Calculator....

Leverage?

Tim
It doesn't show or ask the pedal ratio and every car is different. My Wilwood is 6.25:1 Some Mustangs are 5:1 It affects how much force is applied to the master cylinders.

It also assumes a single master cylinder, which many of us have dual cylinders of different sizes.

It's a good resource, just wish it allowed full "tweaking" to match individual cars instead of using some default settings.

Paul
 
Tim I think the way we verified that my rear brakes were not working is about the most accurate way to measure. Why calculate something that you can actually measure to very close tolerances? Those gages are pretty cool.

BTW did you ever try them on your car? If not you should.
 
Hi Gents,

I see quite a few of you have accessed the Bias Calculator from this site.

First let me say that the calculator is designed mainly as a comparative tool and not an engineering tool. There are faults such as a single master and set pedal ratio built into the system which may or may not work for you. On the other hand if you were wishing to compare a change from 11.5" front rotors to 14" rotors (assuming 18" wheels- an example I know) you could see how this effects the cars brake balance. Or a caliper piston size change etc etc.

It's not even necessary to populate all that info to see what happens if you change only one item- the net % change is still quite obvious. Again; that's the primary intent here.

There are some other variables found in twin MC set ups to take into account; bore sizes, balance bar offsets and centering as well as how that pairs with the caliper piston sizing. For the record, pedal ratio has no effect on bias- it's simply a torque multiplier. But in determining that ratio and it's effects on a twin mc set up it's good to have both the short and long dimension to truly calculate that ratio. Also important is the specs of wheelbase, axle weights and a proposed "g" or deceleration desired. All that gets a target number pretty close and within tuning range.

Obviously as you read that...yes I do have other tools to help you get that information and use it to your best needs. If anyone wants or needs to go over some of it I'll be happy to do so on a case by case basis offline. Feel free to contact me at the link above.
 
Some good basic info in there. I'd only take issue with one comment I found odd;

Pads. A pad size doesn't make more friction if it's larger. Ie doesn't make more brake torque. The larger the pad- the longer it lasts. A small variation in it's mounting radius aside a pad that has 2x the square inches simply spreads the the same load in two different foot prints. Torque coming from clamp load if you have the same piston area in a Superlite or a Dynalite the torque is the same. The SL pad is larger and lasts longer, the DL pad just wears out quicker.

An easy way to think of this is by standing on the bathroom scale; if you weight 200lbs in a size 9 shoe, do you weigh more in a size 13 shoe? Shoe weight not withstanding you have more psi in the smaller shoe so the larger one would last longer if you could wear it.
 
Todd I agree. I found a article about shaving away some pad area to change the bias. They took out about 50% of the pad material and only made a 15% difference in torque. So while the surface area of a pad makes little difference, there is a difference. From their testing for every 3% change in pad surface area you will see a 1% change in torque applied to the rotor.
 
Todd, a little background as to why/how this discussion started. Not sure how familiar you are with the "cobra"/ "daytona" coupes you are, but basically, we are finding more weight is distributed to the rear of the car - mine for instance is 57% rear to 43% front with my big block. I believe Mike's coupe is close to that as well. The theory Mike is working towards is a 60/40 rear biased brake setup. His thought is more weight / bias to the rear means more even braking. I somewhat agree with that, but lean more towards being front biased since there is some weight transfer to the front plus forward motion equals more weight on the front during hard braking.

The objective for us both is to not have the back end of the car swap ends under hard braking in to a road course high speed corner. Mike and I have been back and forth on this, with some great discussion and I know I've learned a lot, but would be interested in your thoughts as well. We all know center of gravity, type of brakes, and tires all have something to do with braking successfully, just looking for that balance (I am anyway) for street and track if there is one. Thanks for checking in with us.

Tim
 
mmarshall said:
Todd I agree. I found a article about shaving away some pad area to change the bias. They took out about 50% of the pad material and only made a 15% difference in torque. So while the surface area of a pad makes little difference, there is a difference. From their testing for every 3% change in pad surface area you will see a 1% change in torque applied to the rotor.
Click to expand...

Be interested in seeing more specifics of this. There are some variables here that should be considered also.

The reason is based upon not what was remove but where it was removed. Looking at a typical DL pad which is roughly 4 x 1.75 if you reduced that to 3 x 1.75 you should not see any change at all. But by removing the 1" of pad you've also negated the pressure point of one of the two pistons pushing on it- clearly making it not overly effective and unable to apply pressure to the plate.

If you take some of that off the long side and make it a pad of say 4 x 1" then you have done two things: first you have negated the effectiveness of the pistons above. But you've also altered the center point radius of the pad. This in turn changes the Er or effective radius of the pad and more importantly the torque arm of sorts.

Many of the race pads are long and skinny. Street pads are short and fat. The reason is that street pads need longer life and a more stable operating platform. A track pad is skinny and places the pressure point out on a higher radius- this forces the pad to work harder and on a narrower strip of rotor band. And that would make it more effective- in turn taking away some of that will reduce this.

All things being the same: if you run a 12" rotor with a 2.5" pad vs a 1.5" pad you'll get much more brake torque with the narrow pad. But you'll run it hotter and and faster too.
 
Purple Venom said:
Todd, a little background as to why/how this discussion started. Not sure how familiar you are with the "cobra"/ "daytona" coupes you are, but basically, we are finding more weight is distributed to the rear of the car - mine for instance is 57% rear to 43% front with my big block. I believe Mike's coupe is close to that as well. The theory Mike is working towards is a 60/40 rear biased brake setup. His thought is more weight / bias to the rear means more even braking. I somewhat agree with that, but lean more towards being front biased since there is some weight transfer to the front plus forward motion equals more weight on the front during hard braking.

The objective for us both is to not have the back end of the car swap ends under hard braking in to a road course high speed corner. Mike and I have been back and forth on this, with some great discussion and I know I've learned a lot, but would be interested in your thoughts as well. We all know center of gravity, type of brakes, and tires all have something to do with braking successfully, just looking for that balance (I am anyway) for street and track if there is one. Thanks for checking in with us.

Tim
Click to expand...

Get me some of the hard data mentioned and I can help you with that Tim. Mike is partially correct as are you; more rear weight can allow for more rear braking. (why do you think a Porsche is so good under braking?) But it also has to be balanced between both static bias and dynamic bias. Static is easy- pick a part and so some math. Dynamic is more difficult and requires some more calcs and some projections.

Actually know a bit about the cars...managed Bondurants shop here in AZ for 4yrs long ago and then did side work sharing shop space with the old HiTech shop in Tempe where I assembled a few of their cars/products and did some resto work on an original. Clearly no expert here, but I own a set of Witworth wrenches and sockets! :D
 
I have not found the article yet but here is a good one to read. They are talking about Tim's brakes!

http://www.circletrack.com/chassistech/ctrp_0409_proper_brake_system/viewall.html


"Performance Friction representatives say they generally like to see front brake temperatures 150-300 degrees higher than the rear. If it's greater, then you are probably not getting the full potential from your rear brakes. This will result in the front brakes being overworked, and the fluid in the calipers will boil, which will seriously degrade your ability to slow down in the turns."


Read more: http://www.circletrack.com/chassistech/ctrp_0409_proper_brake_system/viewall.html#ixzz1lO7bjeXb
 
I found it! My numbers were off a bit. They reduced the pad area 2/3 and reduced brake torque by 17%. So it was 1% reduction in brake torque for every 3.88% reduction in pad surface area. So the ratio is closer to 4/1.

http://www.stockcarracing.com/techarticles/scrp_0412_race_car_brake_bias/viewall.html


Here is what I found: The motor with no brake load pulled 9 amps. With full brake pads, I applied pressure to the brake pedal. At 450 pounds of pressure, the Amprobe read 12.1 amps, indicating an increase in load. The difference in the amp readings is an indication of the amount of load being applied to the brake. Or, in other words, this is the power that is being absorbed by the brake (braking effect).


My next step was to cut down the pad area. If some's good and more's better, then too much should be just right. I reduced the pad area by two thirds. Of course, the pads will wear faster when cut down.


Back on the machine, I found that 450 pounds on the pedal only loaded the brake to 10.2 amps on the motor. I pressed on, pun intended, until the Amprobe read the same 12.1 amps as in the first test. At this time, the brake line pressure was standing at 600 pounds. It now took 150 more pounds of force to get the same braking effect of the full-size pad. Or, to put it another way, the same brake line pressure produced 17 percent less braking force with the cut-down pads.


Read more: http://www.stockcarracing.com/techarticles/scrp_0412_race_car_brake_bias/viewall.html#ixzz1lO9WTVRs
 
Yikes....folks just shouldn't be allowed to publish such ideas. You guys do realize also that by grinding a pad like that the piston is almost pushing around what's left in the center of the pad? Guessing that's a 2.5" piston or so and applying a very odd load to what's left of the pad. The pad wear got quicker...you think? And as they wore down they got more effective when the ground portion got back in contact with the rotor. Maybe ok for some Saturday night circle track race, hardly what I'd want on a street car.

I won't argue the reduction, percentage or ratio or whatever. If this type of backyard tuning floats your boat- be my guest. I'll stick with more safe and sound engineering principals here.

If you really have a brake balance issue look at fixing it the right way or building things with the proper parts to begin with. Much easier.
 
Ford Mod's

Tim
This article may be of interest to you. The guy was trying to improve the brakes on a 95 SuperCoupe Thunderbird. This is where the "bracket" to fit 11.65 rotors came from.

Fraleigh Brake Mods

I just made a set this morning. Took me about 1 hr and I am ready to mount the larger rotor with the Ford SuperCoupe caliper.

Don't know what you have on the front but it may be appropriate for that also

Paul

hope I posted this to the correct thread. I think there are about a dozen on brake improvements/balance :)
 
PaulProe said:
Tim
It doesn't show or ask the pedal ratio and every car is different. My Wilwood is 6.25:1 Some Mustangs are 5:1 It affects how much force is applied to the master cylinders.

It also assumes a single master cylinder, which many of us have dual cylinders of different sizes.

It's a good resource, just wish it allowed full "tweaking" to match individual cars instead of using some default settings.

Paul
Click to expand...


Been some time since I recall the conversations here. Time to refresh the mind again.

Paul: you were asking for more tweaks?

DUAL MC and Brake Torque Calc.
 
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