Brake question

this may be a dumb question but here goes
when changing from drum to Disc., why do you have to change the proportioning

The reason I ask is, when I changed mine over to Disc. I never changed the valve, I only changed the master cylinder.

I don't have any brake problems, what problem if any will this create.

Wrong forum - moved....

The problem you will have is on a panic stop the rear will lock up well before the fronts (from a pressure standpoint). Ideally lockup occurs at the same pedal pressure.

Just a suggestion,,,
Ditch the stock valve and put in an adjustable one from Ma' Mopar, Wilwood, whomever. You will be suprised at how more responsive your brakes will be once they are adjusted in properly.
From a tech aspect, you want the fronts to lock just before the rears. I know you all will snivel about being able to turn a locked wheel, but if you have ever had a the chance to panic on wet pavement and had your rears lock first, you will know what I am talking about. I did a four wheel lock with an abs car on ice once, man, that was interesting.....