K-G

So my master cylinder is leaking and I need to replace it.
I figured since I’m going to be swapping over to rear disc within the next month I should just get the 15/16th MC from the 91 civic so I don’t need to replace my booster also.

My question is All the research I’m doing, some people are recommending a 40/40 proportion valve and others are saying it’s fine without one.
Do I need a new proportioning valve when installing 15/16th MC & rear disc conversion ?
Im unsure as what to expect now and would like to do it right.

K-G

The car is a 93 civic EX btw

GIZZ - EXV

Abs or no abs? If non abs get the 40/40 valve, makes a huge difference should you ever need to brake hard with limited traction.

Tyson

Increasing the size of the master cylinder is not going to help anything. I wouldn't bother.

If you want the best setup, mimic an OEM system. So if you're planning to change to rear discs, use whatever prop valve and mc that matches what you have.

4040 is just more commonly available. But if you really want the best, copy OEM.