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Disc Brake Engineering Thread

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RRworker

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Hey everyone came across this thread and was wondering if anyone tried to match up the parts from the rockwell/meritor fds-75 or fds-90 axles to deuce axles. If I remember from researching another project that the '84 and newer axles had the option of hydraulic disk brakes. I dont have a deuce yet or measurements of the fds parts but if they would work parts shoildnt be to bad to source or get out of a heavy junkyard. just figured I'd throw it out there.

Howie
 
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bugwhacker

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Moving your hubs out for clearance.

A bit of necro-threading but here is some information for those that are setting up their own front disc brakes.

The "Magic" inner bearing /cup assembly to move your hubs outward for maximum clearance is the 3994 bearing with the 3926 race, It will result in 0.1575" more space over stock or a touch over an 1/8".

A good second is to use your stock inner 3992 bearing with the 3926 race, It will result in 0.125" or 1/8" more space and save you the cost of a bearing.

Some people are running the 3994 as an inner and some are running the 3992, both are acceptable bearings the only real difference is the 3994 is .0325" thicker.
 

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steve6x6x6

steve6x6x6

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bugwhacker said:
A bit of necro-threading but here is some information for those that are setting up their own front disc brakes.

The "Magic" inner bearing /cup assembly to move your hubs outward for maximum clearance is the 3994 bearing with the 3926 race, It will result in 0.1575" more space over stock or a touch over an 1/8".

A good second is to use your stock inner 3992 bearing with the 3926 race, It will result in 0.125" or 1/8" more space and save you the cost of a bearing.

Some people are running the 3994 as an inner and some are running the 3992, both are acceptable bearings the only real difference is the 3994 is .0325" thicker.
Click to expand...
I have been using the timken 3926 for 14 years with my brakes.
 
rustystud

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I believe if you used "Peashooter's" stainless lines and New Dual circuit Master Cylinders with these Disc brakes, you would have the perfect system. It would be able to stop the Riggs with the Mega Tires, and it would have excellent serviceability. No more having to take the wheels off to adjust and check your brakes. Easy replacement of Pads versus replacing of shoes, (which are going extinct). For those who go off road, the clean-up would be far easier then drums. Plus when your seals leak ( of course no ones seals ever leak ! ) you won't be coating your shoes and drums with oil, creating a hard to stop vehicle (especially with those Mega Tires ! ).
It does mean you have to come up with another air pac, but you will not be trying to retrofit a HydroBoost system to your vehicle. No hydraulic pump to add to your engine. No hydraulic hoses to play with, or worry about leaking. You would keep your stock brake pedal and linkage, No messing around under your dash.
Your truck would enter the modern world. :)
 
outcast

outcast

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rustystud said:
I believe if you used "Peashooter's" stainless lines and New Dual circuit Master Cylinders with these Disc brakes, you would have the perfect system. It would be able to stop the Riggs with the Mega Tires, and it would have excellent serviceability. No more having to take the wheels off to adjust and check your brakes. Easy replacement of Pads versus replacing of shoes, (which are going extinct). For those who go off road, the clean-up would be far easier then drums. Plus when your seals leak ( of course no ones seals ever leak ! ) you won't be coating your shoes and drums with oil, creating a hard to stop vehicle (especially with those Mega Tires ! ).
It does mean you have to come up with another air pac, but you will not be trying to retrofit a HydroBoost system to your vehicle. No hydraulic pump to add to your engine. No hydraulic hoses to play with, or worry about leaking. You would keep your stock brake pedal and linkage, No messing around under your dash.
Your truck would enter the modern world. :)
Click to expand...
On a Bob'd deuce yes, but I don't know if that master cylinder has enough volume to operate disk on two back axles, and the front.
 
rustystud

rustystud

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outcast said:
On a Bob'd deuce yes, but I don't know if that master cylinder has enough volume to operate disk on two back axles, and the front.
Click to expand...
You think a Hydroboost master cylinder has more volume then the dual master cylinder the M35A2C does ? If you would compare the bore sizes of the two you would see there is little difference, plus the volume to activate the calipers comes from the air-pacs.
 
mudguppy

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yes, few vehicles came with them, however, most any MD and below vehicle comes with them now. I was poking at the 'modern' part since that's what any truck in it's GVWR class would come with today.

just poking.
 
mudguppy

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outcast said:
On a Bob'd deuce yes, but I don't know if that master cylinder has enough volume to operate disk on two back axles, and the front.
Click to expand...
disc brake caliper pistons require less volume to operate than a comparable drum slave cylinder. The extension of the slave cylinder is much much farther than a caliper piston.
 
peashooter

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mudguppy said:
disc brake caliper pistons require less volume to operate than a comparable drum slave cylinder. The extension of the slave cylinder is much much farther than a caliper piston.
Click to expand...
Im pretty sure it's the other way around. Disc brakes require more fluid volume than drum. Vehicles with disc in front and drum in rear need a split ratio master cylinder to put more fluid to the discs and less to the drums.
 
steve6x6x6

steve6x6x6

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peashooter said:
Im pretty sure it's the other way around. Disc brakes require more fluid volume than drum. Vehicles with disc in front and drum in rear need a split ratio master cylinder to put more fluid to the discs and less to the drums.
Click to expand...
No sir, disc brake calipers do have larger bores BUT only need to travel .010 to .015 thousands of an inch for lockup.
 
peashooter

peashooter

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steve6x6x6 said:
No sir, disc brake calipers do have larger bores BUT only need to travel .010 to .015 thousands of an inch for lockup.
Click to expand...
Well I don't want to argue but every article I have read is to the contrary. I just googled "disc drum brake volume" and they all say disc requires more fluid volume. Perhaps there is something unique about the Rockwell drums and discs that fit but I would be surprised.

" Drum brakes will require less fluid and pressure than disc brakes. " - http://www.mbmbrakeboosters.com/ind...linder&catid=6:which-part-is-for-me&Itemid=14
 
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