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Discussion Starter · #1 ·
Does anyone know alot about hydroboost brakes or can point me to some place that does?
I just put a 1600 lb. camper on top of the truck and want to improve my braking with the boat behind the truck/camper. The boat trailer has surge brakes that work very well but need to see a somewhat rapid stopping action from the truck. Now that the truck stopping is slower I cannot actuate the boat brakes nicely. I'd like to find out somehow if my hydroboost can be improved. When I bought the 2001 Dodge hydroboost unit and the master cylinder that mates to it there was no actuating pin with either part. This is the pint that transfers the hydroboost piston motion to the master cylinder piston. I had to make my own pin becasue I could not buy one from Dodge. I was wondering if anyone knows if this pin length can have an effect on how much power steering hydraulic pressure is divided between the braking action and the power steering. I have way more steering power than I need. I can steer the truck with my little finger.

I also was thinking of experimenting with inserting a restrictor valve or pressure regulator in the boost line that comes out of the hydroboost unit and over to the power steering pump.

Any expert opinions or ideas on this?
 

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Discussion Starter · #4 · (Edited)
It's been marginally better than the vacuum assisted brakes even when I don't have a load on the truck. Wondering if I made that pin/pushrod too long or too short. I don't have another known good rod to compare it to.

MAC: The master cylinder is for a 2001 Cummins equipped Dodge truck. I assume it would have been either a 3/4 or one ton truck. The master housing is bigger than the 1/2 ton cylinder was.
 

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Discussion Starter · #5 ·
Think I have my solution. I may have made a mistake by going to the 2001 master cylinder. It's a larger bore than what I had. I called hydra Tech brake booster people and they said I need to go at least 1/8" smaller on the master cylinder bore size to get better braking.
 

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Discussion Starter · #8 · (Edited)
It does make sense. See How stuff works:
http://auto.howstuffworks.com/brake1.htm
By making the master cylinder smaller you get greater multiplication of working force at the larger brake piston. If the master cylinder piston is one tenth the size of the brake piston you get a 10x force increase at the brakes. So as I make the primary piston (master cylinder) smaller, say 1/20 the size of the brake piston, I get a 20x increase in force at the brake piston. I just have to move the brake pedal a little further. I will be changing from a 1 1/4" primary piston to 1 1/8". Wonder if I can find a 1" master cylinder and make this truck rip up asphalt when I stop.
 

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look. heres what you need to do FIRST.

check the length of the rod between the two.the rod should be JUST shy of depressing the master when the two are bolted up.

check to see if you have any air in the lines etc.

now you need to see what your pedal ratio is. its supposed to be around 5/6 to 1. divide your entire pedal length (pivot to tip) by the pivot to boost rod length.

if all that is ok, i guess try another master.

a smaller master may apply more force, but its going to require a LONGER stroke of the pedal. i dont know how much, but it will.
 

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Lee is right on. I used to use 1 & 1/4" bore masters with my hydroboost. My pedal stroke was to long. On a hard stop my pedal was near the floor. I now use a 1& 5/16 bore MC and have great brakes and normal pedal travel. I use thsi 1 & 5/16" bore MC on all my trucks with hydroboost. MC is a Bendix 11584, NAPA # 39017

Paul
 

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Discussion Starter · #12 ·
The 1 1/8" master cylinder is in place. It works great. The pedal travel is simular to vacuum assisted brakes now; about 2 1/2" of travel. It's easy to lock up the tires with very little pedal force.
My pedal working advantage ratio is whatever was in the 2000 Dodge Ram. I had to convert the truck from an automatic; adding a clutch brake assembly from a newer parted out 2000 Dodge.
The previous setup had a very stiff pedal so I don't think I had air. The actuating rod I made for the new assembly was prefitted and adjusted just making contact at the hydro and master ends as I tightened up the bolts.
Thanks for all the suggestions.
I talked to HydraTech for a while on the phone and he said that the Dodge hydroboost I have in place does not have a very high boost advantage compared to the aftermarket units. Don't know if this is sales talk or what. What hydroboost is everyone using?
 

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I like what mcinfantry says here and will add a bit, if you ever decide to upgrade to rear disks you will be better off with the larger master cylinder.

Also, the power steering gearbox inlet has a valve in it. If your satisfied with the steering, you could try a different valve, it may "balance" for lack of better wording your set-up.

Are you a member of the TDR? There are many, many threads/posts on Hydro steer there.

Here's some tech on increased steer, detune the opposite is worth a shot.

http://westtexasoffroad.homestead.com/powersteering.html
 

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Great Stuff! Im running the GM stuff and was getting ready to change the MC to a larger bore. Man I would have been disappointed. Truck will stop well but I have to stand on the peddle and not much peddle travel. Thanks abunch.
Carl
 

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Discussion Starter · #15 ·
Back to Mac again. I have had this hydroboost on for about 1.5 years now and have not had any more air come out into the reservoir. I used to have pedal kickback in the beginning when i installed it but that has stopped long ago. I still have to try the new master with the camper on top and the boat behind that.
Thanks SD. Sounds like a good idea. I was wondering before I changed the master cylinder how I could increase flow at low rpms.
I wish i knew how the hydroboost splits the pressure off to the gearbox. I have way more power steering than I need and would like to figure out how to force the hydroboost into using more of the pressure that is normally diverted to the gearbox.
Does anyone have a good source for how the hydroboost splits the pressure/flow between the braking and steering?
 

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Here is what I found when I added Saginaw Power Steering to Power Wagons/WC's and M37's that did not come equipped with PS. The stock Saginaw PS Box provided way to much assist. With the front wheels on the ground, I could spin the steering wheel with my little finger with little resistance. There was simply to much assist with no road feel. I contacted AGR Performance Power Steering in Fort Worth, Tx.

They suggested that since the Boxes I used were take outs to have them rebuilt and have the torsion valve changed to a #210. I went with their suggestion back in 2000 on my first Power Wagon. Since then, I have always had them rebuild my boxes and change the torsion valve to a #210.

The steering effort with the #210 valve is what I consider equal to my 2003 Ram CTD.

I am sure any competent steering box rebuilder could change this valve. I have never had a Saginaw Box open to see what is involved with ths change.

This #210 valve change along with Hydroboost that I buy from Hydra Tech and a 1 & 5/16" bore MC gives me perfect stering and brakes on my trucks.

Paul
 

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Landcruiser Hydroboost Hard Pedal

We got the hydroboost all hooked up and it stops the truck ok, but the pedal is hard and doesn't have much travel. The brakes have been bled a bunch of times and the steering works great with no noises or foam. I'm thinking we might need to lengthen the pushrod. Any suggestions?

Carl Donica how did you resolve your similar issue?
 

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Sounds just like my brakes. Im going to the parts store saturday to get master cyl. with a smaller bore, this should allow more peddle travel and less peddle pressure.
 

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Let me know how it works and a part# if you have one.

Thanks
 

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Veggie, sorry for the delay. Found a master cylinder that was only 1/16" smaller bore( 1 1/4 vs. 1 5/16) than what i was running. Small town and "in stock" is kind of limited. However just this minute amount made my brakes a lot better. Factory brakes on this truck had 1 1/16 bore. If I could have located a 1 1/8 bore that I didnt have to modify my brakes would have been awsome. Ill be changing front diff to D60 later and they may get better/worse. But I know how to attack now. Part# 10-1534 at O'reillys and Parts Plus should get you what you want if you go with this bore (GM late 70s-early 80s JD-7 series brakes). If your wheel cylinders/brake calipers are still stock, you could go maybe a 1/16" larger than the trucks original master cyl. bore for the best results. Anything smaller than what you currently have will be better.bounce
Carl

1979 F-250 crew cab 4 x 4
4 bta with modified H1C
Cold air intake
ZF S5-42 5 speed
Borg Warner 1356 x-case
Dana 60 rear
Dana 44 front
3.55 gears
255/85R16 tires (33.5x10.5)
Hydroboost steering and brakes
Custom 40 gal. fuel tank
Much more later
 
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