drums to disks front on 45s

[4sum4]

Do i need to replace the master cylinder aswell when doing this,its an 81 model

[MY45]

You shouldnt need to but you will need an proportioning valve for the rear brake line.

I got an adjustable one from rocket industries. The adjustable ones are not meant to be run if the can be adjusted with out using tools but my engineer didnt care/notice.

[beanz2]

If the front was drum, the master may have a higher residual pressure valve to counter the return springs. This needs to be removed if used with discs up front, otherwise the brake pads will drag on the rotor.

In older cruisers it is usually a brass valve screwed into the side of the master. You can replace it with one from any disc brake Toyotas of similar years.

Dave

[4sum4]

this what got

[beanz2]

this what got

See the larger hexagonal valve that the brake line screws into? That is where the RPV is. See if you can remove it from the front circuit and get rid of the mechanism inside. Often it is just a simple spring or a rubber flap.

Dave

[4sum4]

Now looking at replacing the master cylinder with the 80s,Already have the prop valve and hard lines to bolt up,Will i need a LSPV for the rear?

[beanz2]

I'm also running an 80 series master in my 75. I have no LSPV for the rear circuit but I don't expect to load her to the limit.

It is interesting in the 80 with ABS and viscous transfers the rear brake circuit comes off the front connector of the master and the front circuit comes off the rear conn. I think it isn't reversed in the non ABS 80. Somebody correct me if I am wrong.

Dave

[4sum4]

I don`t no much about brakes but correct me if i`m wrong aswell?but i think the ABS MC from the 80s would be usless on a 45s aswell on my 85 4runner???

I`m planning on doing rear disks on both vehicles

[4sum4]

is this what your talking about

[beanz2]

The RPV is a brass valve screwed into the side of the master in the pic below. Inside you can see a little plastic valve held in place by a rubber flap. In this HJ75 master, I can feel a difference in the tension between the front (disc) and the rear (drum) RPV's.

The valve is prone to rounding off when you try to remove it, be sure to use a flare nut wrench or remove the brake line first and use a six-point socket insted of a twelve-point.

Dave