[nodwyer]

Did a front disk conversion manual with manual drums in the rear. Front brakes fine lock up on panic stops. Rears do not, Any ideas.

[Goatracer1]

What was included in you conversion kit?

[rexs73gto]

Did you use the same prop valve, & if so that is your problem. You'll need a prop valve that is adjustable so you can dial in the amount of brake pressure goes to each end.

[69FIREBIRD76MM]

I installed rear disc on my 69 firebird, the only thing I added was a adjustable wilwood brake proportioning valve. So far it works great on the street and the track too. Disc take less pressure to stop than drums.

[NeighborsComplaint]

You need a disc/drum proportioning valve.

[SMW]

You need a disc/drum combination valve and you do not want the rear brakes locking up.

[lust4speed]

Except the original drum/drum brakes did not have any sort of proportioning valve and relied on smaller wheel cylinders to reduce braking to the rear. If there truly is not a proportioning valve in the system, there should be too much back brake.

Almost all kits come with a new proportioning valve (many already installed just under the master cylinder), and I would suspect that one is now in place and working overtime in limiting back brake action.

I have had much better luck with the adjustable valves. While the car manufacturers were very precise in fitting the correct valve to the specific vehicle, I'm pretty sure that the aftermarket vendors pretty much use the one size fits all approach. A proportioning valve with too heavy of spring either because of poor design or simple malfunction would incorrectly limit pressure to the rear.

[Scarebird]

Originally Posted by lust4speed

Except the original drum/drum brakes did not have any sort of proportioning valve and relied on smaller wheel cylinders to reduce braking to the rear. If there truly is not a proportioning valve in the system, there should be too much back brake.

Almost all kits come with a new proportioning valve (many already installed just under the master cylinder), and I would suspect that one is now in place and working overtime in limiting back brake action.

I have had much better luck with the adjustable valves. While the car manufacturers were very precise in fitting the correct valve to the specific vehicle, I'm pretty sure that the aftermarket vendors pretty much use the one size fits all approach. A proportioning valve with too heavy of spring either because of poor design or simple malfunction would incorrectly limit pressure to the rear.

very true.