had an issue of lacke of suffiecnt brake monday on long island ny though i was able to keep form lettign a big truck(full size day cab car hauler) drag his trailer over the front of my truck (i was even with his trailer tires), though i wasnt able to keep from rear ending him. and only my trailer tires barely left marks. the prodigy P2 work on the tow vehicles decell rate. rolling less then 9 tons everything should have locked up! before this happen i have bleeded the entire brake systems runing 1qt of new fluid through both front and rear systems each. i had boiled the brake fluid in stop in go traffic friday. brake fluid was black when i checked it, it is now clear.
so with that embarresment said.. time to up grade brake system or make it right.
from what i have found the front and rear are identical size wise rotor dia and caliber...
front runs strictly 5 hole vs rears 10 hole.
MC bore is 1.25" and disc/disc setup running 1/2-20 primary and 9/16-18 secondary. IDk why the front is bigger.. my 02 had a 37mm (1.44") bore 1/2-20 on both systems.. also the wrecker system runs dual 2.6" piston vs the single 3.5?" that the non wrecker has.
the idea is use the GMT800 MC which will reduce brake application time and increase hyd pressurre on the caliber pistons. upgrade to then dual piston which will increace additonal force on to the pads.
before some of you start yelling that im messing up read the following. read the insert that i typed up while back on a malibu forum aat the end of the post.
i have done similar swap/upgrdae on my 75 K20. first up graded to hydro boost. then i went from a hydro 1 1/8" bore MC to a 1 5/16" MC pedal travel was cut roughly in half from ~1" to 1/2" to apply the brakes. and much more brakeing force with less effort on me.
i have a hard time beliveing that there is a disc.drum MC on my truck right now. i also have the JF9 system it is 13.86/13.58 disc/disc were as the JB8 is 12.5 disc and 13x2.5 drum later is the most common
im looking more to mechanics of it.. speed of the brakes applieing and hyd forcce one can create.
if we remove hyd/vac booster(which adds addition applied force to MC piston) and say an avg man can apply 600lb of force on the MC piston and an avg stroke of the piston is 0.75" and to simplifiy things for debating purpose its a single piston MC so volume is stroke (.75")x bore= in3
so the formula for HYD force is piston area x force applied to piston. IE 10LB applied to 1sqin =10psi.
knowing that with the mechanical force and oem brake pedal and avg person can apply 600lb of force to the MC pushrod. i will keep that as a constant. and the max stroke distance of .75" constant as well though it would on refer to speed at which the brakes can be applied in realtion to the brake pedal moving.
i am leaving out HYD/VAC booster since both very drasticly based on engine vaccum/power steering pump pressure setting. all they do is supply addition regulated force to what ever your foot is appling to the MC thus allowing the operator to have to push less harder on the pedal to reach suffiecent pressure to slow the vehicle. it is much simpler to discuse a basic manual system and would like your opinion on HYD pressure one can create at the MC.
a 7/8" bore has 2.74sqin 600lb will generate 1644psi of HYD force
a 24mm bore has 2.96sqin 600lb will generate 1776psi of hyd force.
a 1 1/16 bore has 3.33sqin 600lb will generate 2000psi of hyd force.
a 36mm bore has 4.45sqin 600lb will generate 2600psi of hyd force.
like your thumb tac example i am only talking about the part you press your thumb on. i know fo fact that the rear wheel cylinders are .75" bores which is 2.35sqin this would be pin part of the tac. with the smallest bore info i posted this wheel cylinder wouldl generate 3863lb of mechanical force against the rear brake shoes. this results in the MC having to travel 85% of the distance the wheel cylinder has to travel before making contact with the drum. this transelate into long brake pedal travel.
pedal feel and travel. a smaller MC piston will be easier to push then a larger piston the downside to smaller driving piston is it have to travel farther to net same travel results from the wheel cylinder then a larger driving piston.
the weird thing is the smaller MC the operator will actually be pushing harder on the smaller driving psiton to get sufficent force to stoping force at the brakes then the larger MC.
heres an example keeping the same 3/4" dia wheel cylinder lets hypotheticly say 3800lb of mech force locks up the rear tires and 3500lb is considered a hard stop. from 2 pharagraph up we already know if an operator has a 7/8 bore MC he is goign to need appliy 541lb of force on the MC via the brake pedal with the MC traveling 85% of hte distance the wheel cylinder has to travel.
if the operator has a 1 1/16 bore the operator will only have to apply 447lb to the MC via brake pedal. this MC only has to travel 70% of the distance the wheel cylinder has to travel.
with that said it would be evident to say the bigger MC allows for quicker application of the brakes and with less pressure applied via the operator to reach the hard braking threshold.
with those examples its clear to say a bigger MC will increase braking capability if everything else remains constant in the HYD brake system...
now the booster reduce the amount of force the operator has to put to the MC via the brake pedal.
a 7" diapharm with 15inhg applied to it will generate max of 1271psi of regualted force on the MC thus drasticly reducing the amount force the operator has to applie via the brake pedal.
a HYD boost is much more the power steering pump is set between 900-1000psi at the pressure releif valve operating is about 850psi with a 1 1/4 bore in the booster with a max applied pressure of 3336psi of regulated force that can be applied to the MC on top of what the operator applies.
