What brake balance is needed for a Mustang with a Torque arm? - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 9 Old 07-28-2015, 06:02 PM Thread Starter
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What brake balance is needed for a Mustang with a Torque arm?

From everything I have read the TA, helps keep the car from nose diving in a severe brake.

This means the rear brakes are helping stop the car more so than a stock Mustang as there isn't as much weight being transferred to the front. Correct?

So, IF this is true, then what would be the proper balance on lets say a Fox Mustang with 13" Cobra front setup, and an SVO Mustang rear brake setup 11" rotor/73mm calipers?

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post #2 of 9 Old 07-29-2015, 11:02 AM
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As a data point I run Stoptech 4 piston, 13 inch setup in front and PBR 12 inch, single piston in rear (from an 90ish ZR1 Corvette). I do have a Brake bias adjuster plumbed in and it is necessary or the rear will lock up first. I am not sure to what degree it is employed.


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post #3 of 9 Old 07-29-2015, 05:25 PM Thread Starter
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I had a front brake kit that came with a brake pressure gauge on the proportioning valve. It told in the instructions at what psi to run it.

Might be a good idea to add one to this build [brake pressure gauge].
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post #4 of 9 Old 07-30-2015, 12:23 PM
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Quote:
Originally Posted by mtrain2000 View Post
From everything I have read the TA, helps keep the car from nose diving in a severe brake.

This means the rear brakes are helping stop the car more so than a stock Mustang as there isn't as much weight being transferred to the front. Correct?

So, IF this is true, then what would be the proper balance on lets say a Fox Mustang with 13" Cobra front setup, and an SVO Mustang rear brake setup 11" rotor/73mm calipers?
I have not seen adding a TA to make a dramatic enough difference to require a change in caliper size. Yes, the torque arm reduces weight transfer to allow more rear braking, but there are other factors that have just as large an impact, and they vary with time. An adjustable proportioning valve is all you really need when you don't have ABS, and no calculation or caliper piston area ratios will give you the best answer for all conditions.

Example: A set of new 100-treadwear tires on a 70 degree sunny afternoon will cause substantially more weight transfer than a set of used 300-treadwear tires on a cloudy 37 degree morning waiting for the dew to evaporate in 80% humidity.

I don't think you will run out of adjustment on the prop valve, but if you do, you'll know it's time to make a caliper change, and then continue to use the prop valve for varying conditions/tires.

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post #5 of 9 Old 07-30-2015, 08:34 PM Thread Starter
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All that I've heard about TA's have me really wanting to know how the car feels with it.

I'm just having a hard time waiting to get my car out to a track, or heck, even a late night romp down a deserted road.

First I need the main hoop for a roll cage to get things moving again. The rest of the bars I should be able to install/weld myself as long as they don't need any extreme bends.
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post #6 of 9 Old 07-30-2015, 08:35 PM Thread Starter
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Related question. Can you still buy SVO Mustang rear rotors? From what I've read they are much thicker than the Cobra rear rotors, at somewhere around .95" thick.
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post #7 of 9 Old 07-30-2015, 11:37 PM
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They are a 1984-90 Lincoln Mark VII rear rotor. 0.945" thick.

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post #8 of 9 Old 08-03-2015, 04:39 PM
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MM indicated that they left the stock Fox Mustang anti-dive in their K-member. I assume they designed the K primarily to be used with their T/A. But as Frank pointed out, I found more rear traction with the T/A which added some under-steer; not anything noticeable with brake torque bias. But then I was moving from a rod-ended PM3L. The switch to the PM3L was the dramatic change from a suspension/traction point of view.

I've also found that the torque bias calculators help compare one combo to another and can indicate whether you're close or way off. If way off, the prop valve doesn't have enough adjustment. I generally look at the factory torque bias set-up for a given OEM car and then go from there. You need the caliper and rotor specs. Pad compound, pedal ratio, M/C size, etc, can be help constant for comparison purposes.

So for comparative purposes, given a Cobra PBR with 38mm twin pistons and 13" rotor up front, and an SVO 54mm single piston caliper and 11.25" (?) rotor out back, the brake torque bias is 55% to the front.
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post #9 of 9 Old 08-04-2015, 05:31 PM Thread Starter
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Quote:
Originally Posted by qtrracer View Post
MM indicated that they left the stock Fox Mustang anti-dive in their K-member. I assume they designed the K primarily to be used with their T/A. But as Frank pointed out, I found more rear traction with the T/A which added some under-steer; not anything noticeable with brake torque bias. But then I was moving from a rod-ended PM3L. The switch to the PM3L was the dramatic change from a suspension/traction point of view.

I've also found that the torque bias calculators help compare one combo to another and can indicate whether you're close or way off. If way off, the prop valve doesn't have enough adjustment. I generally look at the factory torque bias set-up for a given OEM car and then go from there. You need the caliper and rotor specs. Pad compound, pedal ratio, M/C size, etc, can be help constant for comparison purposes.

So for comparative purposes, given a Cobra PBR with 38mm twin pistons and 13" rotor up front, and an SVO 54mm single piston caliper and 11.25" (?) rotor out back, the brake torque bias is 55% to the front.
Thanks QT.
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