[cj5] disc conversion trouble : low pressure behind

hallo everybody


ok i put new brakes on my cj (stock leaf but revlover shackle = +1 inch and my tire are 7.5x16 (oem: 6.00x16 wrote on dashboard)

front = rotor and pads from suzuki jimny

rear = rotor and pas from suzuki vitara

beetween the mc and the caliper i put an hydrovac fom mg/a . on front very very good break , but rear low pressure on the rotor ! bleeding is ok (pedal method + vaccuum + pedal) .

the rear caliper wor well : tested , no rust

my system is :










- navy blue = oem brake line

- red = new irgid brake line (copper)

- green = aviation brake line

- light blue = oem suzuki jimny line (caliper/axle)

- very light blue = to intake manifold for depression

- repartiteur jeep = proportionning valve

- pipe admission = intake manifold

- ar d or g = rear break

- av d or g = front break


i ve read a lot of topic before ask you . i found this one : http://www.earlycj5.net/forums/showthread.php?95651-Are-these-stock-brake-parts/page2

the picture of the problem ! http://s1262.photobucket.com/user/Elislives/media/brake3.jpg.html



before i ve read this special topic , i thought that what i call "repartiteur jeep" was a proportionning valve . if i understand the topic , it s not !


how can i solve my problem ! i hope my english is not a problem !

have a nice day

greg

 

thnaks


when i look to the rear rotor they re not polished like front , i can see rust ray on . when i push the pedal you feel that front work fine but rear is not .

diameter i dont know exactly but front are bigger than rear .

the year 1968 . on that part no electrical wire . the switch for brake are further on the line (one for front , one fro rear)

 

Realize that the front brakes do a lot more work than the rear brakes. When you stop, the weight of the car transfers mostly to the front wheels. If you applied the same force to the front and rear, the rear brakes would lock up and the tires would skid long before the front brakes.

Car manufacturers take this into account when building the car. They use smaller/weaker brakes on the rear wheels. Also, the rear brakes wear out more slowly than the front brakes.

Do you know that the brakes are balanced front to rear?

 

the caliper are in good shape ! i ve tested them with test pedal . no rebuilt


ok , i ll try this test !



the problem is taht i don t really know if it s really a proportionning valve ! and perhaps i didn t understant the link , but some of you are not sure too.

 

i know that . it s why i put the biggest (tuffest) in front and the light on the rear axle .

front : rotor with ventilation (sorry for this word but i dont know it) diameter 287mm and lenght pad 117mm , height 45.8mm
rear : "simple" rotor diameter 288 mm and pad lenght 104mm , height 45.7mm



Do you know that the brakes are balanced front to rear? i don t really understand what you say ... what i understand is : rear or front , the rotor were mounted on the front of the car , both jimny or vitara have drum brake on rear .

greg

 

I looked at your Profile and I assume:
You still have a 68 CJ?
And are the pedals and Master still attached to the frame?
I also looked at your photobucket pictures............what Master cylinder do you have in there? There was two in your photo's
Disc's systems require a Master Cylinder with a larger reservoir...........much like one of those in your photos..........If the Master is still mounted on the frame it will also require a 2 PSI residual valve. And if you still have the pedals on the floor you should also check your pedal ratio. Discs require more mechanical pressure in the system versus a basic drum system...............Normally manufactures accomplish this by first using the correct sized Master cylinder bore matched to the needs of the volume of the individual piston sizes at the calipers along with the correct pedal ratio so that your leg that is pushing has enough mechanical advantage.

 

Yep , Howard all of the above..........to many unanswered questions......... be it an unmatched system, proportioning valve , or a residual valve...........I'm just poking holes in the dark!

 

i know that . it s why i put the biggest (tuffest) in front and the light on the rear axle .

front : rotor with ventilation (sorry for this word but i dont know it) diameter 287mm and lenght pad 117mm , height 45.8mm
rear : "simple" rotor diameter 288 mm and pad lenght 104mm , height 45.7mm



Do you know that the brakes are balanced front to rear? i don t really understand what you say ... what i understand is : rear or front , the rotor were mounted on the front of the car , both jimny or vitara have drum brake on rear .

greg

 

i try to answer .

my pedal and mc are stock . i use the hydrovac because in don t want to modify too much and in france it s not really easy with the autority .

1968 cj5 jeep/kaiser


my pictures are not mine but take on the forum .

i ve tested my mc is ok . if i push the pedal i ve the same volume of break fluid which go out . i ve pull away the non-returning valve on the mc .if i kept them the break stayed push a the maximun . the car can t run after a push on the pedal .

 

actually , il i touch the pedal the jeep becomes to break . if i push hard like emergency stop , the front wheels silde on the road . i dont t have to product much force on the pedal to stop the jeep . it s almost like on normal car .

 

its not the same jeep with or without . our little roads in mountain have a lot of curves , we need real break ! i don t regret my hydrovac fb

 

So what I am reading here is, with the rear jacked up and the engine running and tranny in gear (rear wheels turning) and you apply the brake hard, it will not drag the engine down (no brakes)?

 

no , i didn t jack yet the jeep . i ve to do it .

you feel it on the road , that s not : no break but bad break feeling on the rear .

 

As a side note and not entering into the discussion on how to repair the brake problem, I did note something from the brake diagram that concerns me. The description notes copper brake lines. Note a good idea.

Ed

 

why copper is not a good idea ?

 

Copper lines can work harden and fail (crack). A better choice is steel, stainless steel, Cunifer or Nicopp tubing.

Ed