Psdiesel74
Registered User
I've done it before and never had an issue. How would it be putting anybody at risk. Infact I've ran 42" iroks and had no problem stopping or locking up after the proportioning valve
Disc brake dually
- Thread starter Psdiesel74
- Start date
I'd be curious to see some math on drum vs disc size to generate a certain braking force and to dissipate a certain amount of heat. Compare weight of disc vs drum? Sq in of friction material? Not sure what measures are useful or not. We have one guy here saying no issues and can lock the rears with conversion discs and 42" tires and properly adjusted proportioning valve. If he can lock the tires that tells me it's just fine in the braking force department.
My concern them would be brake fade with those discs vs drums. Drums are not great at dissipating heat. Even the large drums on my Galaxie are only good for one stop from highway speed in a short period of time... and at 70+ the last 10-20 MPH takes significantly more force if you're stopping in a hurry. Maybe the smaller discs don't have issues until far more weight than an empty truck, granted with huge amount of rolling mass. I wouldn't knock it until I had more data or was able to compare from experience or back to back.
Regarding hydroboost... Yeah it sounds pretty nifty but it will not give you any more stopping power than vacuum assist. You just need to push harder, that is all. Most of my life I've driven vehicles with manual brakes. My first time driving a vehicle with power brakes I just about sent my passenger through the windshield. If you can lock the tires with a vacuum booster (or no booster) a hydroboost isn't gonna make it stop quicker, just easier. I've locked the tires and threshold braked my truck with new rubber on a dry road while avoiding hitting someone violating the right of way, so while I may eventually switch to the luxury of hydroboost I do not expect any improvement in braking performance.
My concern them would be brake fade with those discs vs drums. Drums are not great at dissipating heat. Even the large drums on my Galaxie are only good for one stop from highway speed in a short period of time... and at 70+ the last 10-20 MPH takes significantly more force if you're stopping in a hurry. Maybe the smaller discs don't have issues until far more weight than an empty truck, granted with huge amount of rolling mass. I wouldn't knock it until I had more data or was able to compare from experience or back to back.
Regarding hydroboost... Yeah it sounds pretty nifty but it will not give you any more stopping power than vacuum assist. You just need to push harder, that is all. Most of my life I've driven vehicles with manual brakes. My first time driving a vehicle with power brakes I just about sent my passenger through the windshield. If you can lock the tires with a vacuum booster (or no booster) a hydroboost isn't gonna make it stop quicker, just easier. I've locked the tires and threshold braked my truck with new rubber on a dry road while avoiding hitting someone violating the right of way, so while I may eventually switch to the luxury of hydroboost I do not expect any improvement in braking performance.
fsmyth
Full Access Member
My 0.0018385 worth:
Heat:
Drum brakes are fine. Until you start to really work them. Then you cannot get enough
friction with HOT linings. Wait until you are pulling 50,000 lbs, and trying to make it down
a decent sized mountain. There is a reason for all the catch ramps.
Depending on the caliper size, number, and pad construction, disc brakes do not exihibit
this behavior until well into material destruction. I have had the discs so hot, it caught
the road grime and crud on fire. Still stopped fine to put out the fire(s). The brakes are
still functional (it is basically a yard truck now. so there was no need to replace anything).
Pedal feel:
No assist - you can feel any tiny problem in your system. Good for building up right leg.
Vacuum assist - isolates you from road feel. Amplifies pedal force pretty much linearly.
Hydraulic assist - also isolates road feel. More exponential force amplification. Considerably less pedal effort.
Air brakes - less direct control over braking action. NO pedal feedback. Almost no pedal effort.
All types can lock up the wheels when properly maintained and adjusted.
ABS and other anti-lock mechanisms can interfere or augment any of the above.
Air and hydraulic systems almost require some sort of anti-lock. Your average driver is generally going to
lock them up in a panic stop, making things worse.
My preference: hydraulic and discs with anti-lock and a functional proportioning valve (no ABS).
Combination is very hard to beat. Just don't jump out of a vacuum brake system into a hydro.
Could break a windshield.
Heat:
Drum brakes are fine. Until you start to really work them. Then you cannot get enough
friction with HOT linings. Wait until you are pulling 50,000 lbs, and trying to make it down
a decent sized mountain. There is a reason for all the catch ramps.
Depending on the caliper size, number, and pad construction, disc brakes do not exihibit
this behavior until well into material destruction. I have had the discs so hot, it caught
the road grime and crud on fire. Still stopped fine to put out the fire(s). The brakes are
still functional (it is basically a yard truck now. so there was no need to replace anything).
Pedal feel:
No assist - you can feel any tiny problem in your system. Good for building up right leg.
Vacuum assist - isolates you from road feel. Amplifies pedal force pretty much linearly.
Hydraulic assist - also isolates road feel. More exponential force amplification. Considerably less pedal effort.
Air brakes - less direct control over braking action. NO pedal feedback. Almost no pedal effort.
All types can lock up the wheels when properly maintained and adjusted.
ABS and other anti-lock mechanisms can interfere or augment any of the above.
Air and hydraulic systems almost require some sort of anti-lock. Your average driver is generally going to
lock them up in a panic stop, making things worse.
My preference: hydraulic and discs with anti-lock and a functional proportioning valve (no ABS).
Combination is very hard to beat. Just don't jump out of a vacuum brake system into a hydro.
Could break a windshield.
LCAM-01XA
Full Access Member
Uhm, how can you have anti-lock but no ABS?
And yea, my concern with the small calipers is not their clamping force but rather their heat dissipation abilities - considering how much of a ***** the rotors on these conversions usually are to change I'd hate to warp them easy, but what I'd hate evern more is to overheat the calipers and lose any contribution to the braking effort they may have had in the beginning. The E350 axle factory calipers are about the size of those our trucks got on the front axle, Dana/Ford weren't messing around there.
As for the vacuum vs. hydro debate, yes aboslutely if you can lock up the wheels with vacuum the hydro isn't gonna do you any improvement in braking, just gonna work the ABS harder. Thing is tho, rears are easy to lock up either way, what would be interesting is how many can lock the fronts with vacuum? Cause with the hydro that ain't all that hard, which on slippery terrain can make for some interesting experiences (as one of our members just found out and now needs to replace half his cab), but some hot dry and sticky road surface is a whole another ballgame...
fsmyth
Full Access Member
To me, anti-lock is wheel-specific, i.e., there is a controller/valve on each wheel.
It monitors that wheel only.
ABS is the modern-day implementation, with some sort of main controller that
watches ALL the wheels, and possibly the steering wheel position, and can have
a gyroscope to detect travel angles. Disguised as Electronic Stability Control,
Electronic Braking System, and other names.
These types are great for your average driver in a panic situation, but seriously
add to stopping times for drivers that are capable of modulating the braking
action themselves. I am sure that sooner or later, someone will release a
system that works well 100% of the time. Maybe they already have.
And the proportioning valve, if properly adjusted, will lock ALL the wheels
at one time. The valve, as shipped from the factory, fails miserably in
loaded vs. unloaded pickups. But it is better than nothing.
Just my 0.03124
It monitors that wheel only.
ABS is the modern-day implementation, with some sort of main controller that
watches ALL the wheels, and possibly the steering wheel position, and can have
a gyroscope to detect travel angles. Disguised as Electronic Stability Control,
Electronic Braking System, and other names.
These types are great for your average driver in a panic situation, but seriously
add to stopping times for drivers that are capable of modulating the braking
action themselves. I am sure that sooner or later, someone will release a
system that works well 100% of the time. Maybe they already have.
And the proportioning valve, if properly adjusted, will lock ALL the wheels
at one time. The valve, as shipped from the factory, fails miserably in
loaded vs. unloaded pickups. But it is better than nothing.
Just my 0.03124
fsmyth
Full Access Member
I really should, to be fair, have added that as I get older, the latest systems begin
to look much more useful. I don't have the reflexes I used to have, nor do I pay
as much attention to driving as I did while racing. Nor do I drive the same types
of vehicles that I did.
And also - folks that drive in ice and snow are undoubtedly going to have a
different opinion.
to look much more useful. I don't have the reflexes I used to have, nor do I pay
as much attention to driving as I did while racing. Nor do I drive the same types
of vehicles that I did.
And also - folks that drive in ice and snow are undoubtedly going to have a
different opinion.
G. Mann
Full Access Member
I'll jump in on this.
I have two 92 trucks, so apples to apples comparison. One is an F 450 cab chassis dually with discs on all 4 wheels and hydroboost, the other is an F 350 dually with drums on rear, vacuum assist.
450 weighs about 1,500 lbs more than the 4 dr. long bed 350, yet it stops, loaded or empty like a sports car... the 350.... better plan ahead and keep several car lengths space, loaded or empty...
Like the OP, if someone came up with a disc conversion that fit a dually install, cleared the dual wheels, and had a park brake.. I'd be all over it in a heartbeat.
I have two 92 trucks, so apples to apples comparison. One is an F 450 cab chassis dually with discs on all 4 wheels and hydroboost, the other is an F 350 dually with drums on rear, vacuum assist.
450 weighs about 1,500 lbs more than the 4 dr. long bed 350, yet it stops, loaded or empty like a sports car... the 350.... better plan ahead and keep several car lengths space, loaded or empty...
Like the OP, if someone came up with a disc conversion that fit a dually install, cleared the dual wheels, and had a park brake.. I'd be all over it in a heartbeat.
i have both too and like you,i had the same experience.
yeah,the f450 with it's massive brake calipers and hydroboost stops super when at maxed out gross.
i have what you have but with hydro on the pickup and with the hydro you can stop just as good at maxed out gross (and beyond) as the f450.
im not making this stuff up guys lol.it's not the disc brakes that makes all the difference.it's the hydroboost.it's night and day.the force it puts on the brakes,be it pads or shoes will totally transform your truck.
of course to all those who have done the swap are reading this like im telling them the sun will come up tomorrow like it did today.
The control and the fact you can lock up all 4 wheels if no ABS.. RFN compared to maybe sometime if I push hard enough on a vacuum truck.
I swapped out vacuum to hydro with correct pedal and hydro mc
There was No other changes made...now my truck is amazing to drive not scary...on ice or compact snow I can if I want lock up fronts easy however it is also very easy to modulate pre lockup point.
The HYDROBOOST brake system is the single BEST improvement that can be made to the trucks braking system BAR NONE! and in all likelyhood the best upgrade for the truck..better tha turbo or big tyres or guages or....insert choice here...but it is really if done right...that big of a difference.
JM100,000,000,000,000,000,000,000,000CW
I swapped out vacuum to hydro with correct pedal and hydro mc
There was No other changes made...now my truck is amazing to drive not scary...on ice or compact snow I can if I want lock up fronts easy however it is also very easy to modulate pre lockup point.
The HYDROBOOST brake system is the single BEST improvement that can be made to the trucks braking system BAR NONE! and in all likelyhood the best upgrade for the truck..better tha turbo or big tyres or guages or....insert choice here...but it is really if done right...that big of a difference.
JM100,000,000,000,000,000,000,000,000CW
raydav
Full Access Member
Allow me to clutter the discussion a bit. The challenge with getting advice from other private users is that everyone's sample size is small, as is mine.
I have two relevant vehicles. One is a 2001 E350, cutaway, 7.3 PSD, dually, 11700 pounds, 4w disk. I have not yet gotten the parking brake to work.
The other is an 84 E350. It came with a 460/C6. Then, in order, went to: E4OD, dually, 1989 7.3 IDI, remote turbo. 9000 pounds.
The master cylinder is a reman from one of the chain parts stores, I don't know which at the moment. The rear shoes are the best NAPA had to offer: $70.
I have six vehicles that run, and the 84 van has the hardest working brakes of the lot. I must be careful or loose objects land in the front, or the rear wheels lock up. Locking the rear wheels is not a good way to stop, but once you have that ability, what more can you do to improve the rear brakes?
I will now answer my own last question, hot performance. The 84 and 2001 have Power Slot disks. They have both been on miles long, steep downhill runs. The 84 cracked the previous, stock rotors. The first pads on the 2001 chattered when hot. The second faded. It now has Ford pads which seem to be better hot than cold.
Brakes are not simple.
Ray
I have two relevant vehicles. One is a 2001 E350, cutaway, 7.3 PSD, dually, 11700 pounds, 4w disk. I have not yet gotten the parking brake to work.
The other is an 84 E350. It came with a 460/C6. Then, in order, went to: E4OD, dually, 1989 7.3 IDI, remote turbo. 9000 pounds.
The master cylinder is a reman from one of the chain parts stores, I don't know which at the moment. The rear shoes are the best NAPA had to offer: $70.
I have six vehicles that run, and the 84 van has the hardest working brakes of the lot. I must be careful or loose objects land in the front, or the rear wheels lock up. Locking the rear wheels is not a good way to stop, but once you have that ability, what more can you do to improve the rear brakes?
I will now answer my own last question, hot performance. The 84 and 2001 have Power Slot disks. They have both been on miles long, steep downhill runs. The 84 cracked the previous, stock rotors. The first pads on the 2001 chattered when hot. The second faded. It now has Ford pads which seem to be better hot than cold.
Brakes are not simple.
Ray
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ok,i hear ya.however i have a challenge for you too.
find 1 person who has taken the same exact small sample (same 1 truck) who with their vacuum assist setup,then swapped to hydroboost and claimed no,or little noticeable difference.
it's going to be a very,very hard challenge because it's someone who doesn't exist lol.
i wanna see a youtube vid of a pickup loaded to max dually gross (about 11k lbs) locking up the wheels with a factory vacuum assisted brake system please.
tip; for those with srw and oem pickup beds,you need approx 2 ton in the back.actually probably more since you've only 2 wheels to stop out back,but we'll let that slide.
safety tip; for the love of god don't try this with traffic anywhere in site and prepare to be grossly disappointed.
Al said it best.he's right.if someone told me they had to remove my turbo or my hydroboost and i had to go back vacuum or n/a.i really would have no choice.id be going back n/a.the turbo would be long gone before id ditch the hydro.so he's right.it is the best single mod we can make to our trucks.we're not just saying this.
don't not swap to rear disc (so long as they're hd truck calipers and you retain an e-brake) but do swap to hydro first is the main point here.
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fsmyth
Full Access Member
Challenge accepted.
This poor little ford F350 I have now has done it numerous times.
Usually loaded with a small dozer or small track-hoe on a 34' or longer trailer.
It is not hard to do on smooth concrete pavement and no trailer braking.
It DOES take some serious pedal effort.
That said, it is totally scary. It generally only happens when you least
expect or don't want it. And it can be eliminated by moving the load
farther forward and putting more weight on the truck.
My sample size is a little larger than one. I have owned numerous 3/4 and 1-ton
trucks and vans, a few 1/2 ton's, a few medium duty (4500-5500 series), and
a few heavy duty - 2 Pete's, 1 Autocar, 1 Diamond Reo, and a 200-ton oil field
rig (A-car, IIRC, it's been a long time).
And driven/used considerably more than that.
Hydraulic assist is fairly new to me - only had it for the last 10 years or so.
IMHO, it's the way it should have been done in the first place.
And also FWIW, I presently have 2 medium duty trucks - 1 Chev. C70 with
air brakes, and 1 GMC 60 series with hydraulic assist and discs on all wheels.
Both stop well.
I cannot report on the GMC, since it is a cab/chassis only, and I have hauled
no loads with it, but it has NO trouble locking all the wheels.
Bottom line - hydraulic assist for control. Discs for continued effectiveness under load.
This poor little ford F350 I have now has done it numerous times.
Usually loaded with a small dozer or small track-hoe on a 34' or longer trailer.
It is not hard to do on smooth concrete pavement and no trailer braking.
It DOES take some serious pedal effort.
That said, it is totally scary. It generally only happens when you least
expect or don't want it. And it can be eliminated by moving the load
farther forward and putting more weight on the truck.
My sample size is a little larger than one. I have owned numerous 3/4 and 1-ton
trucks and vans, a few 1/2 ton's, a few medium duty (4500-5500 series), and
a few heavy duty - 2 Pete's, 1 Autocar, 1 Diamond Reo, and a 200-ton oil field
rig (A-car, IIRC, it's been a long time).
And driven/used considerably more than that.
Hydraulic assist is fairly new to me - only had it for the last 10 years or so.
IMHO, it's the way it should have been done in the first place.
And also FWIW, I presently have 2 medium duty trucks - 1 Chev. C70 with
air brakes, and 1 GMC 60 series with hydraulic assist and discs on all wheels.
Both stop well.
I cannot report on the GMC, since it is a cab/chassis only, and I have hauled
no loads with it, but it has NO trouble locking all the wheels.
Bottom line - hydraulic assist for control. Discs for continued effectiveness under load.
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fsmyth
Full Access Member
I guess I should have added - I considered moving the GMC's hydraulic braking system
to the Chev. winch truck, but the axle was too small. I don't know if you can GET
hydro on a 70 series, but it would be nice to have. The truck is just small enough
that it would work out, I believe.
to the Chev. winch truck, but the axle was too small. I don't know if you can GET
hydro on a 70 series, but it would be nice to have. The truck is just small enough
that it would work out, I believe.
Because the drums on the 10.25 are so simple to setup and do maintanence to I would never consider discs unless that is already on the rear end like a newer 10.5 rear.
The fact people want discs and are likely going to utilize the current vacuum/drum brake MASTER CYLINDER ....tells me plenty.
The factory MC and booster where never engineered to function with discs.
That being said; adding the hydro and using the correct master and pedal then positions one to add a fully capable a d functioning rear disc setup.
I often wonder if the cqddy calipers a d hydro would indeed be effective.
As I am in a very good position to test this theory....(read I hqve caddy calipers complete already) it may indeed happen if I come across the correct discs and a set of decent brackets.
I can always retur to a working drum setup if need be and the aforementioned zwap provez useless.
I can mqybe thi k of perhqps 1 other upgrqde equal to or maybe surpass hydroboost.
BETTER HEADLIGHTS.
I feel I can drive slower qnd stop even faster with better brakes than drive faster and stop slower...longer...
JUST SAYIN
The fact people want discs and are likely going to utilize the current vacuum/drum brake MASTER CYLINDER ....tells me plenty.
The factory MC and booster where never engineered to function with discs.
That being said; adding the hydro and using the correct master and pedal then positions one to add a fully capable a d functioning rear disc setup.
I often wonder if the cqddy calipers a d hydro would indeed be effective.
As I am in a very good position to test this theory....(read I hqve caddy calipers complete already) it may indeed happen if I come across the correct discs and a set of decent brackets.
I can always retur to a working drum setup if need be and the aforementioned zwap provez useless.
I can mqybe thi k of perhqps 1 other upgrqde equal to or maybe surpass hydroboost.
BETTER HEADLIGHTS.
I feel I can drive slower qnd stop even faster with better brakes than drive faster and stop slower...longer...
JUST SAYIN
+1 for anything to improve headlights. Quality halogen sealed beams help but not significantly. Gonna do relays on mine and see how much that helps. Looking at better reflectors and higher wattage bulbs once the framework is there.
My biggest problem with brakes on these trucks, rear brakes specifically, is the hub seal leaking gear oil all over new brakes. The newer two piece seal helps a lot but I've had a couple problem axles that eventually started leaking again. Maybe that is part of the reason so many seem to want discs in the rear?
My biggest problem with brakes on these trucks, rear brakes specifically, is the hub seal leaking gear oil all over new brakes. The newer two piece seal helps a lot but I've had a couple problem axles that eventually started leaking again. Maybe that is part of the reason so many seem to want discs in the rear?
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