# Hydraulic theory

Discussion in 'Old's Cool' started by kellymac530, Sep 21, 2011.

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I saw a thread a while back on on brake theories and master cylinder vs. caliper/wheel cylinder sizes to change braking forces.

That thread had alot of equations and I am a moron...so I am looking for some simplified input.

This is for a non motorcycle application, but it will all cross reference and it is an old's cool vehichle.

I have a 1952 Studebaker pick up truck. It is a rare 3/4 ton single rear wheel. Very odd one. It has 14" x2" rear brakes and I will be checking out the fonts in the next day or 2 so I will update...BUT, Many have mentioned that the old drum brakes are very weak at best. I AM going to keep it all drum in the interest of the vintage cool factor, but I do want to improve efficiency.

I will give the exact MC piston sizes asap but the rears wheel cylinders I know are 1-1/8".

If I go with a bigger piston on the MC and leave the stock wheel cylinders will that improve braking force and lessen the amount of foot pedal pressure to required to accomplish the same stopping forces? Or will increasing both MC and WC sizes be better? Decreasing WC and Increasing MC?

How about adding a power brake booster MC/ That will just decrease foot pressure I believe but NOT add any actual stopping power...correct me if Im wrong.

I am thinking if I can desin and fab up a modern power MC out of some 1 ton GM etc.. truck and maybe increase the WC size to 1-1/4" that may improve my braking force and stopping power. The 1 ton truck versions of old Studes had 1-1/4" WC and they interchange on the backing plates and I believe they came in 1" as well.

So without the E=Mc2 type of formulas can I get some input on possible improvements?
2. ### Grider PirateLong timer

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Increasing wheel cylinder size will increase the amount of force you exert on the brake shoes. That's good. However, it will decrease the amount of travel available to move the shoes. Not a problem if you keep them adjusted reasonably well.
Going from 1 1/8" cylinders to 1 1/4" should yield something like 25% more force to the shoes.

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Ok, so it will help to increase the stopping force, but will make the pedal travel farther towards the floor..correct?
4. ### Grider PirateLong timer

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Yup! Significantly

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Well then...How did a bigger truck back in the day stop better with a load than a smaller truck would with the same load?

Back to a bigger MC and a bigger WC?

:huh

My peanut brain is melting. I had no idea peanuts could melt.
6. ### Grider PirateLong timer

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Because the bigger trucks had MUCH bigger DRUMS too! My 1965 Dodge 3/4 ton truck had ENORMOUS brake drums. My '69 1/2 ton Chevy didn't. Hauling the same bikes in the back, the Dodge stopped with much greater authority. The RATIO between the MC piston area and the WC piston area determine how hard the shoes will push against the drums for any given amount of force applied to the MC.
Kind of the bottom line is this: It's an old truck without power brakes. Expect to push pretty hard on the pedal to stop it!

EDIT! I have used both feet on the brake pedal (they're wide for a reason) of an early 60's truck hauling a load of gravel. Women didn't drive pickups back then.

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No big pedal here it is manual trans and has a little round pedal the size of a regular soup can ish.
The truck actually has huge drums on it...14" is a big drum. A half ton chevy has 11" drums most years and 12" on others and often only 1.5" wide. Mine are 2" wide. These are huge comparatively. these are as large as a modern 1 ton dually drum is...Well modern before most went to disc anyway.
8. ### Grider PirateLong timer

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One of these days I'll have a modern truck with disks all around. My 2001 Ram 2500 still has (shitty) drum rear brakes.
9. ### villageidiotLong timer

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i put a master cylinder and booster from a chevy colorado into a 1970 scout for a friend of mine, and it was like stepping on a pillow, and locking up all 4 corners

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Modern trucks are over rated. I just got rid of an '09 Chevy 2500 HD X cab with the 6.0 gasser and the 7 speed AT trans. GREAT truck for sure, but boring and just like every other chevy on the road. I wanted a change. Studebaker, thats a pretty big change I think...

Power MC booster is likely what I will end up doing. I guess I am just thinking out loud and trying maximize every dollar I will spend on the truck. I dont mind buying new parts especially on brakes, but not having ever driven a '52 Stude 3/4 ton truck before I was just think if I have to buy new parts and there are options to improve them up front that this may be a smart choice. Actually the guys on the Stude Drivers Forum I am also on say the brakes on that truck should be fine especially since I am not planning on carrying tons of weight.

Wheel cylinders and MC run the same price for 3/4 and 1 ton truck and seem to be interchangeable with only bore diameters being different, so I was just thinking that upgrading while I am buying them may be smart, but maybe not.

I appreciate all of the input. I WILL need more help over the next weeks....make that months
11. ### sh0rtlifeLong timer

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something i dont see mentioned is pedal travel vs force required...and add to that arm length and leverage point.....sadly you pretty well have to guess and make it up as you go and tho the "theory" and mathmatics of it are out there..explaining and understanding it are 2 different things..and in the end your llikely better off starting in one spot and experementing...but if you can goto a bigger wheel cyl id do it!!!

is that truck got the brakes in the floor or on the firewall?.....regardless i would look at willwood/tilton/howe style stock car brake setup with DUAL MC's 1 for the front 1 for the rear...reason being is then you can start with one size mc and change sizes till the force vs travel starts getting right......id likely start with something like dual 7/8s setup..you can pickup used ones off ebay for pretty cheep and rebuilds for them is also cheep....and if your pedals are in the floor then doing a lil modding to get such a setup under the truck would be a walk in the park and easily adapted to the stock pedal ...if its on the firewall...it may prove to be alot more trouble.......

how did the trucks do it back then..bigger parts..mc and wc's..really but alot of stopping as downshifting too

have to agree on modern trucks being over rated...for that matter cars too....some things are nice but the good old tactile feel gets lost the newwer you get...as well as the fun simply goes away....id avoid going power anything if you can help it...but an OD unit would DEFFINTALY be on my list..but likely an old brownie or a lil bugger like what im cooking up
12. ### batoutoflahondaLong timer

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I've had a few old Willy's Jeeps and they had tiny MCs. To get them to stop well you really had to be diligent on adjusting the WCs, (they all wear differently) and learn to down shift effectively. Really, if it's just sort of a fun thing, I'd leave it stock. Maybe reline the shoes with better material, build new brake lines free of rust, and appreciate driving a machine that requires a bit of skill.
13. ### motuLoose Pre Unit

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The brakes on something of that era will most likely be duoservo (floating anchor) and putting a booster on it will make the brakes almost uncontrollable. Boosters are a must for disc brakes as they have no self servo action,the servo action on duoservo is very powerful.
14. ### redprimoBeen here awhile

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Back in high school I had a 50 jimmy pu and the brakes were one system I never had problems with. Those vacume winshield wipers, now thats another story...

Actualy the biggest problem I had was that the back end was so light that It was really easy to lock up the rear end when running around town without a load. I learned to drive in a stick so using the gears to slow comes natural to me and I never had any problems getting that beast to stop.

As for modern brakes. I am currently well on my way to warping a second set of front rotors in my 2001 7.3L F250 4x4. It does stop better when pulling a load than the 76 F250 did but when empty it is no better.
15. ### sh0rtlifeLong timer

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anyone who thinks a booster is a MUST on disc's hasnt doen there research...the RIGHT size mc/s will mean you dont need a booster on anything EVER..look at well every race car on the planet..discs and no booster and some INSANE huge discs

the big worry on the old stuff is that single cup feeding all 4..anything goes wrong and youve got NO brakes anywhere..been there on my 58 ford a few times ...rebuilt the mc in the sake of keeping the old charm of being all old school and rough around the edges...eventualy i broke down after a few too many scares with that single cup and not having enuf fluid in the system to keep everything from fading out bad and updated myself to a 90s ford truck MC which woke the system up as a bonus of being dual pot..now if got granada disc's up front as well but NO BOOSTER and the pedal feels better than it did with the drums and single pot

ive done alot of disc swaps with and without booster and imo all of the non booster cars have more user feedback to the pedal as to whats going on...and then theres the whole engine dies and look the brakes STILL work the same way..1 or 2 pumps with power and your out of brake more or less on a boosted rig

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Wow I thought I knew car lingo...I have NO IDEA what a duoservo OR a floating anchor is in regards to brakes????

Dual master cylinder?
17. ### sh0rtlifeLong timer

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i wont get into the duo or floating...

but youve got litteraly 3 types of brake MC...you have a single put(more than likely whats on the truck but is what is on every bike with hyd anything)..

in the mid 60's all the car companys had switched over to dual pot IE pop the cap and you have a front and rear section all ran by a single piston..this ment should any end of the car failed..the otehr end would still work..atleast for some time..but being a SINGLE bore and piston your bound to get bleed over

then you have various forms of abs..where in more modern cases the mc is either something so strange and goofy or non existant

now..DUAL mc's is generaly found on well most all race cars built .....theres 2 versions( more if your talking about the mount and having a clutch pedal on the same box)..version 1 is what i consider a semi floating pedal..as in you have an adjuster that slides a rod between the 2 mc's to adjust front and rear break bias..as 1 mc runs the fronts 1 runs the rear..the other typ of dual is a fixed rod where bias control must be done with a proportioning valve in the lines..."most" 30's and 40s style streetrods and on into the 50s pu rods generaly use these setups....im running the same setup in my lloyd

this is a typical unit...youll take 1 look at it and think its an in floor unit..but...flip the mc's over and now you have a hanging unit.....

the second link is a standard race version
http://cgi.ebay.com/ebaymotors/Howe...r_Truck_Parts_Accessories&hash=item588d75db2c

you will note the adition of the clutch...regardless its all basicaly the same design...tho this one can be fliped turned and taken apart and put back together to allow for floor mount forward, floor mount backward, underdash units, thru firewall units..its all in the orientation of the pedal and rotation of the mc units......

they make the mc's is quite a few size ranges...and they are all the same bolt pattern regardless of brand...howe, tilton, willwood, cnc, afco, coleman, us-brake, and a few others i cant recall there names....now mind you the rebuild kits for the mc's are NOT all the same..but there really seems to be only actuly 2 or 3 different designs the rest are all copys......rebuild kits are 10-20\$ per mc
http://cgi.ebay.com/ebaymotors/SWS-...1978793?pt=Race_Car_Parts&hash=item4394f64ea9

its certainly tryed and true tech...poke your head into the newwest nascar or drag car or even gravedigger and you will find one of these units in one brand or another in it....poke your head into some of the "high" end stuff from the 60's and such and you likely find the same setup

there is only really 2 things i can say in regards to the units..1 solid mount them...SERIOUSLY solid mount them cause your foot exerrts a ton of force...secondly is that you will have to play with pedal length ratios and mc size..but to be honest its easier than you could ever imagine..just time consuming

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Hey shorty, I understand what a single pot MC and dual pot mc and dual MCs all are. I was just lost as to the Aussie lingo.

I actually disagree with one thing you said though. You said a single pot is what every motorcycle has tha has anything hydraulic...True and Not true. Yes there is 1 pot, but it is 1 pot for the front and 1 pot for the rear..that = 2 pots. Even if it has a drum rear with a cable or a rod, the front MC only controls 1 axles brakes. Thus I think that the single pot analogy is sort of inaccurate. A dual pot and a dual MC both use a separate tank and a separate piston cup or completely separate piston for each axles brakes. A motorcycle imho is essentially a dual MC no matter what.

Thanks for the links though. My truck has the 40s-50s style that pushes back under the cab with the MC pointing backwards and you have to take a little plate off of the floor to access the MC to add fluid.

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20. ### sh0rtlifeLong timer

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thats the setup i figured you had..into the floor...and your right about the bike setup..it really is a dual mc setup

the nice thing about the dual MC units is if you need to you can stagger the sizes..the bias all that jazz...i mean youve got mcs ranging from 5/8s well over 1inch and thats just off the top of my head....where a dual pot unit your scratching your head and measureing and running part#'s its hell to try and figure out what units bigger and "if" it will mount....the dual setup you just swap em out and if it dont improve enuf you swap it out..its like swapping springs...the fact that you want to retain the old brakes just re-enforces the thinking of useing such a dual setup......and most units can be flipped revered etc is just a bonus...and if you dont mind welding..you can cut off the new pedal and weld in your old one or mod the mount to leave your old one exactly where it is to run the new units......i made my own arms and only used the mount and piviot point on a howe unit