Front disc brake questions

Suspension, steering, brakes, wheels & tires

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sawdust1
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Front disc brake questions

Postby sawdust1 » Mon Aug 14, 2017 10:53 am

I am switching my 69 f100 over to disc brakes. I am not sure what I need as far as master cylinder and booster. Sounds like I can use my original booster with a 73-79 master cylinder?
I've also seen Ultrarangers post using a 95 explorer master cylinder and a late seventies f350 booster. Is this a better option and is it complicated ?
I'm a bit confused
This site is awesome!
Thanks
Bob

ultraranger
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Re: Front disc brake questions

Postby ultraranger » Mon Aug 14, 2017 1:19 pm

Like most everyone else with a Photobucket account, my pictures are hosed up there so, it makes posting photos here more difficult when you no longer can use that site to host them through.

At any rate, I do have most of the photos that are viewable through this link, since photos can be posted directly through FTE without the need for a 3rd party hosting site. This isn't the installation on my truck but, is one I did afterwards on my friend's '72 F100. The only major difference in his booster and mine is that his has an adjustable input rod between the brake pedal and the booster. My booster has a fixed length input rod.

https://www.ford-trucks.com/forums/1452 ... oster.html
Steve

1969 SWB F100 Ranger. 240-6, C-4, 9" N-case 31-spline Traction-Lok w/3.50 gears.

1968 Mustang. My high school car. Owned since 1982.

2003 Azure Blue Mustang Mach1.

sawdust1
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Re: Front disc brake questions

Postby sawdust1 » Mon Aug 14, 2017 8:54 pm

Can I use the proportioning valve I have from a 78 f250? Will the f350 booster bolt right up or do I need to source f350 mounting brackets?

Thanks again

Bob

ultraranger
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Re: Front disc brake questions

Postby ultraranger » Tue Aug 15, 2017 7:41 am

Different GVWs of the trucks will dictate what brake valve was used on them. The cast iron Kelsey-Hayes valve was used on the disc/drum Dentside 2WD trucks with a GVW of less than 6900#. The brass Weatherhead brake valve was used on trucks with a GVW of 6900# or greater.

A brake valve with a higher GVW rating than a lighter truck is likely to cause the proportioning valve circuit in the brake valve assembly to react later, in the event of a panic stop.

I guess what I'm getting at is it's best to get a brake valve from a Dentside/Bullnose truck of similar series and GVW rating. The cast iron Kelsey-Hayes brake valve I installed on my friend's '72 F100 came from an '82 F100/F150.

The brake valve I installed on my truck was for an '84-'86 F150/Bronco.
Steve

1969 SWB F100 Ranger. 240-6, C-4, 9" N-case 31-spline Traction-Lok w/3.50 gears.

1968 Mustang. My high school car. Owned since 1982.

2003 Azure Blue Mustang Mach1.

sawdust1
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Re: Front disc brake questions

Postby sawdust1 » Wed Aug 16, 2017 1:32 am

Thanks again

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MadMike
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Re: Front disc brake questions

Postby MadMike » Fri Aug 18, 2017 3:10 am

I would highly suggest using an adjustable proportional valve when deviating any vehicle from its original brake system.
Compound the problem with different wheel/tires sizes or grip(treadwear rating) front to back, or engine/trans swaps, the required bias will greatly change how the brakes work.

An adjustable proportional valve is also great in that the braking for the truck can be fine tuned for when it is loaded or unloaded.
-Michael

sawdust1
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Re: Front disc brake questions

Postby sawdust1 » Fri Aug 18, 2017 9:36 pm

Thanks Michael

ultraranger
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Re: Front disc brake questions

Postby ultraranger » Sat Aug 19, 2017 9:29 am

A Dentside or Bullnose truck of similar series will be the best source for a disc/drum brake valve that's engineered and dialed into the settings that would be most appropriate for this disc brake swap.

If you have a factory disc/drum brake valve installed, it's not a good idea to add a manually-adjustable proportioning valve aft of the factory brake valve. This would put TWO proportioning valves in series to the rear brakes competing against each other in a panic stop situation. The proportioning valve spool, spring and seal would need to be gutted from the factory disc/drum brake valve, if you were installing a M-A proportioning valve, in tandem with the factory disc/drum brake valve.

If a M-A proportioning valve is being installed, how do you know what 'knee point' and percentage of pressure rise you are adjusting it to? Making some stops, turning the knob, making some more stops, turning the knob some more is simply a guess at what the true setting is being adjusted to. What are the chances that you'll get it dialed precisely to the pressure reduction setting it needs to be set to? --not very likely.

You would need a set of brake pressure gauges to be able to correctly dial in the M-A proportioning valve. Even if you had a set of gauges to tune the M-A valve with, what is the knee point (PSI) figure needed for the Bumpside? I know what it is for an early T-Bird (450 PSI @ 43.5% reduction) or an early Mustang (300 PSI @ 50% reduction) but, I've never seen this pressure figure or percentage of rise figure published for a Bumpside.

If you have no equipment to read the pressure being applied to the brakes, you have no accurate way of knowing what the tuning is simply by turning the knob and seeing if the wheels lock up or not. Then again, assuming you do have a set of brake pressure gauges, you first have to have a known target pressure value to set the M-A proportioning valve to. Without this important bit of information, all adjustments (with or without gauges) will be a guess.

http://stoptech.com/technical-support/t ... ing-valves
Steve

1969 SWB F100 Ranger. 240-6, C-4, 9" N-case 31-spline Traction-Lok w/3.50 gears.

1968 Mustang. My high school car. Owned since 1982.

2003 Azure Blue Mustang Mach1.

sawdust1
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Re: Front disc brake questions

Postby sawdust1 » Tue Aug 22, 2017 12:43 am

Thanks for the very thorough answer guys.

Bob


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