brakes are fixed

[TLBREWER]

It's interesting in just the differences from truck to truck. When I had three trucks, all having the same "hardware" with the exception of wheels and tires, they all had very different braking characteristics. My '92 2WD crew cab would lock 'em up and stand on it's nose with no problem when braking hard. My daughter's '91 4X4 SC has pretty good pedal feel, but not nearly as good stopping power as my old CC. And my wife's truck is a constant battle to keep everything adjusted and operating at what I consider a marginal level. I can lock hers up and stop effectively, but I have to push the pedal into the exhaust manifold to do so...she doesn't have that much strength and adjusts her stopping distances accordingly. Hydroboost is next on my list for the '91's for brake upgrades. My '06 Dmax has it and I love it.

Tom

 

[Jeff Dodson]

Jeffs fix would drive me crazy because the base problem was never corrected.

Ok I'm not understanding this about the base problem. I had changed everything, the M/C three times, even new front calipers, new RABS valve, the rear brakes are fine, adjusted, clean not leaking, nothing frozen. In fact when I put the new RABS valve, I could feel the rears working better. The pedal never changed, It always faded down almost to the floor. Let me tell you, pulling a boat. that scares the hell out of you.

Now back to your statement, THE BASE PROBLEM WAS NEVER FIXED, what else should I have done.

Yesterday, I had to drive somewhere and it was raining. I had to stop quickly had no problems with it stopping, the pedal never faded, the truck stopped straight, no pulling to one side and did not have to put alot of pressure on the pedal. Could this just be one of FORDS screw ups and should have put a M/C on these trucks this size, I hear alot of the same problems on this site.

 

[datkinsonsr]

Your formula just proves what others have been saying is true. If you increase area and do not increase force then pressure goes down.

I guess I should have run my own numbers. I stand corrected. By going to the larger master cylinder, did this also have a larger vacuum diaphragm?

 

[Mont91]

Had a very good short reply, took to long and lost it.

Jeff---You eliminated(not solved) your problem by replacing an original design part with a part of differant design.
Since the improper operation was not corrected using original design componants, we do not know if the issue will resurface at a very bad time as we do not know what the problem was.

The problem also might never return.

On my '91 "properly" adjusted rear brakes do not suffice, I run them up until the shoes kiss the drum. I also recently replaced the non working axle speed sensor and eliminated the little pedal sink I had and improved stoping distance. Maybe the new sensor cycled the RABS unit so that it sealed better?

Jim---Cheap pads will compress slightly and have a lower friction coefficiant thus needing more push on the brake pedal to stop. I am all for quality pads.

Slightly out of round rear drums will compress the wheel cylinders needing more than the allowed amount of fluid to reexpand, while not producing pedal pulse because the brake shoes float a little.

Quick and nasty reply. Feel free to ask for a better explanation.

 

[Jeff Dodson]

I also recently replaced the non working axle speed sensor and eliminated the little pedal sink I had and improved stoping distance. Maybe the new sensor cycled the RABS unit so that it sealed better?

I was not aware that this old of a truck would have an axle sensor. If that was bad, wouldn't it cause the check engine or brakes light come on??

 

[towcat]

Jeff-
don't sweat it. If what you have done works, stick with it and don't look back. Something always gets lost between what the engineers put on paper and what happens in reality. I've dealt with that for too many years. Fact. Stock Ford brakes suck. Anything that can be done to improve on stock is a good thing. GM with all their shortcomings, rarely ever had an issue with their braking systems. That's a known fact. There's even ford guys converting the knuckles on their Dana60's to take GM braking parts so that they can stop and not pay a fortune for hard parts. Another fact. GM has been using hydro sucessfully on all their 1ton gassers since 1973 and on all their diesels since 1983. Anybody who has driven my '92 CC dually, will attest to the fact the damnn thing DOES stop on a dime and that's with drum rears. When I change over to disc rears, I want the truck and gooseneck trailer to stop on a dime Only bad part of hydro is anything that is not tied and secured, will launch into the windshield when you stand on the brakes Oh yea, I also have "severe duty" pads and shoes on the truck.

 

[The Warden]

Another fact. GM has been using hydro sucessfully on all their 1ton gassers since 1973 and on all their diesels since 1983. Anybody who has driven my '92 CC dually, will attest to the fact the damnn thing DOES stop on a dime and that's with drum rears. When I change over to disc rears, I want the truck and gooseneck trailer to stop on a dime Only bad part of hydro is anything that is not tied and secured, will launch into the windshield when you stand on the brakes Oh yea, I also have "severe duty" pads and shoes on the truck.

What he said and that's from direct experience...after getting the exhaust taken care of, I think hydro's next on my to-do list after driving his truck (with an intercooler next on the list)...

Just wondering...for the people who have been arguing against the hydrobost/F-450 m/c setup...have you actually driven a truck set up with this?

 

[jauguston]

Warden,

Correct me if I am wrong but I don't recall any discussion or arguement against hydroboost/F-450 MC setup. There has been discussion about hydraboost and there has been discussion about F-450 MC but I don't recall any discussion of the two combined.

Jim

 

[The Warden]

Jim, I was under the impression that the two basically go hand-in-hand. I think one person stuck with the F-350 m/c; the others who have done the hydroboost conversion also used F-450 m/c's. The F-450 master cylinder goes directly onto the hydroboost unit, while the F-350 m/c needs a slight modification.

Also, I'm not sold on the idea of an F-450 master cylinder being a downgrade. I don't claim to be an expert, but it seems to me that a larger bore on the master cylinder would attempt to push more fluid through the lines, and trying to put more volume in the same space (the lines, and the calipers/slave cylinders themselves) would lead to more pressure, which in this case seems that it would be a good thing. I understand that you disagree with this, but I don't understand why.

I'll admit that I've never driven a hydroboost-equipped truck with an F-350 master cylinder, but towcat's truck (with hydroboost and an F-450 m/c) WILL stop on a dime without even thinking twice. This is compared to my truck, which has a stock braking system (no ABS) in good working order. You make a very good point that good-quality brake pads will also make a difference; it seems to me that the two upgrades combined would really help matters.

For that matter, I wonder how feasible it would be to put F-450 front calipers on the front end of an F-350 (or an F-250 for that matter)? To me, there's no such thing as brakes that stop too well...too bad that it looks like all the rear disc brake conversion kits are for 10.25" axles; I have yet to see one for my Dana 70...

 

[jauguston]

Warden,

We both now agree you don't understand.

Jim

 

[The Warden]

Thanks for clearing that up

 

[yARIC008]

I will vow to if you change the bore to larger you will get harder to brake brakes. I did this exact mod and it was good until i tried to an emergency stop. You simply can't push hard enough. I think just a new master cylinder with the same bore would have been better.

I'm guessing the bigger trucks that use this bigger master cylinder have larger calipers too so it works out to be the same as my van and the slightly smaller master cylinder. Anyways, yes, it's not good. Now that mine is worn in though, it's not too bad, i can brake pretty quickly now.

 

[towcat]

For that matter, I wonder how feasible it would be to put F-450 front calipers on the front end of an F-350 (or an F-250 for that matter)? To me, there's no such thing as brakes that stop too well...too bad that it looks like all the rear disc brake conversion kits are for 10.25" axles; I have yet to see one for my Dana 70...

tim-
F450 calipers are huge compared to the f250 & f350, but the trade offs on being stuck with the 10lug rims isn't worth the re-engineering grief.
as far as the disc brake conversions goes, E350 SRW ambulances are still Dana 70's and they are still our bolt pattern 8lug and 99up is usually disc brake rears. Time to hit the vanner wrecking yards Yup. factory stuff. Buy a rear axle assembly, strip the goodies you need off of it and dump the housing.
jauguston-
your concerns of being able to stop can also be allievieated by sourcing the same rear ends for the E350 and E450 van chassis. 99up dualies come in two flavors. Both are disc brake. One incorporates the parking brake on the assembly the other has no parking brake and you will need to find a driveline brake. Since you are running at max weight most of the time, this conversion may be worthwhile for you.
just a thought.

 

[typ4]

I put a 450 hydro unit on my truck and used the stock F350 mc,a little filing involved, stops way better that the vacuum booster, truck will stand on its nose. Raybestos severe duty pads on the front, stainless braided teflon front brake lines. I don't know what shoes are on the rear, haven't had to change them yet but will go to severe duty friction if I can find it.

Hydroboost unit makes lots of extra room for intercooler piping.

 

[The Warden]

F450 calipers are huge compared to the f250 & f350, but the trade offs on being stuck with the 10lug rims isn't worth the re-engineering grief.

Oh! Didn't realize that that the calipers were that huge...was thinking they could be used with the 250/350 rotors for some reason. Okay, scrap that idea

as far as the disc brake conversions goes, E350 SRW ambulances are still Dana 70's and they are still our bolt pattern 8lug and 99up is usually disc brake rears. Time to hit the vanner wrecking yards Yup. factory stuff. Buy a rear axle assembly, strip the goodies you need off of it and dump the housing.

SWEET!! Did they have a version that incorporated a parking brake like the dualies you mentioned?

I may as well wait until the drums I have now get worn (the shoes are only a year old), but that'll be VERY worthwhile when the time comes...