rear disc brakes cure lockup

[gpp]

if you put rear disc brakes on a 66 mustang along with disc on the front does it get rid of rear brake lockup and swaying side to side?

 

[rbohm]

it will help prevent brake lock up since disc brakes need more line pressure than drums do because they are not self energizing. that said, installing an adjustable proportioning valve to reduce rear line pressure works very well.

 

[65ShelbyClone]

that said, installing an adjustable proportioning valve to reduce rear line pressure works very well.

+1. I mean why put on rear discs just to maybe get the bias right when a $40 prop valve will do the same thing? It's worth mentioning that the front brakes are supposed to lock up first to prevent the back end from coming around in a locked-up panic stop.

The "swaying side-to-side" sounds like a suspension issue to me, not brakes.

 

[gpp]

when i said side to side i meant one side or the other depending on which wheel locks first.i do have a porporton valve in the rear line in conjunction with the stock disc brake porporton valve.should i remove the stock porporton valve to adjust the rear?

 

[tph5443]

Has the suspension been upgraded or is it pretty much stock?
Hard braking and the resulting change in suspension alignment will bring on some drastic bump steer on a stock suspension set up. My 65 does the same thing when I nail the brakes.