Master cylinder for disc brakes

[aj's tonka truck]

I'm installing a D60 front & 14ff rear with disc brake conversion on my 91 Jimmy.
Do I need to install a differant master cylinder to give me more fluid capacity as
well as bigger bore ? Maybe one from a 1 ton. I know the brake calipers on the
D60 are bigger than my 10 bolt had and now I'll have calipers on the 14ff in the rear. I'm planning on installing a knob style proportioning valve inside the cab
so I can adjust the brake bias. I would appreciate any help here I can get.

 

[M-1028]

I did rear discs on my 1 ton with no mods and it works awsome. My buddy put a ff14 and 60 on his 84 1/2 ton burb and it also works great with no mods.

 

[85mudblazin]

Ileft mine all stock also and it works good

 

[mouse]

I completed the disk brake swap last week and it works great with the 3/4 ton MC I'm running. The pedal does have a slightly longer throw before the brakes start to work, but its not anything I would call abnormal. The brakes work great! Nothing like locking up all four 35 inch tires!

 

[aj's tonka truck]

Did you do anything to your proportioning valve? I have read that you have to disable the factory one and install an adjustable one in the cab so you can set the brake bias.

 

[M-1028]

If I were you I would try it with the stock system and if it dosn't work like you want it to you could always install the adj. proportioning valve. I seriously belive the stock system will work fine. Like I said my buddy did the exact same swap as you an has had no problems.

 

[camiswelding]

the hydroboost thread in tech would be a good read for you

 

[Muddytazz]

Every vehicle seems to react differently to the rear disk conversion. On my 3/4ton burb, when I installed mine, I left everything stock (stock m/c, booster, prop valve, lines everything) and have been running that way for close to 2 yrs now without any problems.

 

[mouse]

I did not do anything to the proportioning valve, although I was (and still am) prepared to if the bias seems wrong. Honestly my truck still brakes normally, just stronger than with the drums. I bought the "Large GM" calipers from TSM, and the only negative comment I would have, if you can call it that, is that the parking brake is weak. I lengthened the adjuster with some all thread, and have the cable properly adjusted, but it will barely hold the truck. With the parking brake on it will not roll, but you must really put your leg into getting the parking brake on.