79jasper
Chickenhawk
http://powerstrokearmy.com/forums/showthread.php?t=3940&showall=1 post #13. It's on a psd but still the same brake setup. That's the one I had read. The D80 had rear disc.
Rear Disk brake conversion
- Thread starter laserjock
- Start date
79jasper
Chickenhawk
Wouldn't hydroboost add more force?
I feel like you have something against rear disc conversions. I'm not for it nor against it. But it's really not that big of a deal to correct the pressures.
firehawk
Full Access Member
First thing I would ask is if you have an issue with braking power? If so, I would look into pad selection first, as a conversion is much more expensive and time consuming. My truck has towed 10k+ loads (with trailer brakes) and never had a brake problem. Just use good pads and high temp fluid. My drums also come off without removing the axles, so maintenance is a breeze.
'94IDITurbo7.3
HAMMER DOWN!
the biggest problem is that the drums always back off. i put new brakes on my truck and the pedal was good...............for a few days, then they pedal got low again(still is since i am to lazy to adjust the shoes).
firehawk
Full Access Member
Mine don't. Pedal is firm and consistent. You have a problem. Fix it and you will like the brakes. You can still have the same problem even on a disc setup, so don't blame the drums.
The Warden
MiB Impersonator
I keep hearing about problems with the 10.25 and brakes getting out of adjustment quickly. Do the adjusters not get lubricated properly, or are they wear items that need to be replaced but don't get replaced as often as they should, or is it a design flaw?
Forgive the slightly off-topic question, but I haven't had the pleasure of dealing with a 10.25 yet (my truck has a Dana 70)...thanks in advance
Forgive the slightly off-topic question, but I haven't had the pleasure of dealing with a 10.25 yet (my truck has a Dana 70)...thanks in advance
79jasper
Chickenhawk
I would like to know also. I'm having problems getting mine to work right in my 94.I keep hearing about problems with the 10.25 and brakes getting out of adjustment quickly. Do the adjusters not get lubricated properly, or are they wear items that need to be replaced but don't get replaced as often as they should, or is it a design flaw?
Forgive the slightly off-topic question, but I haven't had the pleasure of dealing with a 10.25 yet (my truck has a Dana 70)...thanks in advance
firehawk
Full Access Member
Don't assume the rear brakes are causing a soft pedal. Air or a leak anywhere in the system can cause that. Not many people flush their brakes, so that might be a good place to start.
79jasper
Chickenhawk
Oh I know. I've replaced the master cylinder. Flushing the fluid is next. Also need to lube the front slide pins.
Since you seem pretty knowledgeable, what's the best procedure for adjusting the parking brake?
Mine goes straight to the floor and barely does anything. I know I need to adjust the shoes some more. But I don't have access to a strong enough jack to get a tire off the ground. My 2 ton floor jack won't budge it. Lol
firehawk
Full Access Member
I do a lot of endurance road racing, so brakes are one thing I know well.
On my truck, the parking brake cable stretched. I installed a large turnbuckle rather than replace the cable, so check that first. On level ground with good bearings, the truck should roll easily. Adjust the drums till they just start to drag. I like to go by ear rather than till I feel it drag, as it doesn't need that much tension. The parking brake should be able to hold it on an incline, but still roll freely when off.
79jasper
Chickenhawk
The cable stretching is one thing I didn't think of. I haven't tried adjusting it yet. Just thought I'd bring it up with someone that has experience with them. A lot of people don't even use them nor care if they work. I on the other hand like a good working parking brake. Especially having a 5 speed during warmup.
Thanks
Thanks
'94IDITurbo7.3
HAMMER DOWN!
i have all new hardware in my drums, good fluid, good master cylinder, no leaks, no air. my adjusters are also clean and lubed up.
Wyreth
Certifiable Noob
Why Wy thinks disk are better... period:
Hydraulic brakes work off two very basic principals, the lever. And hydraulic force multiplication. (a booster, wither hydro, or vacuum only adds more pressure to the lever, so I am leaving them out of this)
Disc brake calipers work off of, and require the exact same pressure that drum brakes do. HOWEVER since they use a MUCH larger piston to achieve much higher levels of force multiplication, they need more fluid volume to work. When you change the rear brakes to disks, they then require more volume. That means more pedal travel before your brakes firm up, we're talking like 1/8th of an inch. The rear brakes will see the same pressure as they did before. Disk calipers exert more pressure; because they use hydraulic force multiplication to do this, they do not require more pressure. They require more volume.
In a perfect world, without friction and heat, drum brakes work much better, and more efficiently than disk brakes. However, from the moment the pad touches the drum/rotor your brakes start fading. (unless you happen to have carbon ceramic rotors/pads which do the opposite) The hotter they get, the less effective they are. Disk rotors shed heat several orders of magnitude faster than drums. Allowing them to grip longer, and "recharge" much much much faster.
Another factor in braking is, as the pad presses against the drum/rotor it sublimates, forming a high pressure pocket of gas between the pad and the rotor. With pads on disks, the "width" of the pad in ratio to the surface of the rotor is relatively low. Allowing the vapor to escape faster, keeping the pad in contact with the rotor longer. (this is why they "slot" rotors for racing applications) This is very much not the case inside a drum, and this can happen pretty quick in a high load application. (did it many times getting stupid in my old 65 mustang)
If you're like me, and that 3/4 ton sticker is simply a minimum load spec, you think about those things looking down a grade.
Not to say that disks are perfect, they wear out MUCH faster. Parking brake systems are.... interesting to work into a rear disk, and while the system can operate under much more extreme conditions than drums can. They're actually more fragile, and dependent on high quality metallurgy to work correctly.
But they're still better.
Hydraulic brakes work off two very basic principals, the lever. And hydraulic force multiplication. (a booster, wither hydro, or vacuum only adds more pressure to the lever, so I am leaving them out of this)
Disc brake calipers work off of, and require the exact same pressure that drum brakes do. HOWEVER since they use a MUCH larger piston to achieve much higher levels of force multiplication, they need more fluid volume to work. When you change the rear brakes to disks, they then require more volume. That means more pedal travel before your brakes firm up, we're talking like 1/8th of an inch. The rear brakes will see the same pressure as they did before. Disk calipers exert more pressure; because they use hydraulic force multiplication to do this, they do not require more pressure. They require more volume.
In a perfect world, without friction and heat, drum brakes work much better, and more efficiently than disk brakes. However, from the moment the pad touches the drum/rotor your brakes start fading. (unless you happen to have carbon ceramic rotors/pads which do the opposite) The hotter they get, the less effective they are. Disk rotors shed heat several orders of magnitude faster than drums. Allowing them to grip longer, and "recharge" much much much faster.
Another factor in braking is, as the pad presses against the drum/rotor it sublimates, forming a high pressure pocket of gas between the pad and the rotor. With pads on disks, the "width" of the pad in ratio to the surface of the rotor is relatively low. Allowing the vapor to escape faster, keeping the pad in contact with the rotor longer. (this is why they "slot" rotors for racing applications) This is very much not the case inside a drum, and this can happen pretty quick in a high load application. (did it many times getting stupid in my old 65 mustang)
If you're like me, and that 3/4 ton sticker is simply a minimum load spec, you think about those things looking down a grade.
Not to say that disks are perfect, they wear out MUCH faster. Parking brake systems are.... interesting to work into a rear disk, and while the system can operate under much more extreme conditions than drums can. They're actually more fragile, and dependent on high quality metallurgy to work correctly.
But they're still better.
hce
So can i....
Does anyone understand that a larger master cylinder ultimately cuts down force applied to the pads, or shoes with the same force applied to the master cylinder piston. A larger master cylinder only provides more volume, so the pads will actually engage. I made a mistake in my explanation of using force and pressure interchangeably. Disk need much more applied force then drums. Give drums a little applied force from the piston and they will make even more applied force from the rotation.
That being said if you can get the appropriate force, disk are going to be a lot shorter stopping distance.
Also please check out faq on any brake site. Please look at the second one down
That being said if you can get the appropriate force, disk are going to be a lot shorter stopping distance.
Also please check out faq on any brake site. Please look at the second one down
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firehawk
Full Access Member
Disc are better in every way. But a few things: brakes work in a heat range based on the pads, and out gassing it not an issue on pads, and have not been for a long time.
Brakes do not start to fade after you hit the brakes, unless you are using cheap organic pads. Good semi metalic pads and ceramic pads actually work better after they have heat in them. Racing pads have almost no grip when cold. I highly recommend buying a good quality ceramic pad. They will perform better and last longer; well worth the cost.
