new 4 wheel disc swap and rears are doing most of the work

[mike63078]

Good mornign all

I purchased front and rear Signature disc brakes for my 67 cutlass. they work well however i need to get the car tuned up since there is low vaccum so i need to muscle them for now. My issue is ther rear brakes seem to be doing most of the work due to the amount of brake dust on the rear wheels compared to the front.

When i did the swap i did reuse my 4 wheel drum distribution block but this should now matter since the one in the kit should not have any metering in it right?

can anyone help as to what might cause this?

[captainofiron]

Good mornign all

I purchased front and rear Signature disc brakes for my 67 cutlass. they work well however i need to get the car tuned up since there is low vaccum so i need to muscle them for now. My issue is ther rear brakes seem to be doing most of the work due to the amount of brake dust on the rear wheels compared to the front.

When i did the swap i did reuse my 4 wheel drum distribution block but this should now matter since the one in the kit should not have any metering in it right?

can anyone help as to what might cause this?

you probably need a metering valve between the rears and the distribution block

sounds like there is a large enough difference in diameter between the front calipers and the rear calipers piston that the pressure in the hydraulic system is causing different forces front and rear

(force is pressure x area)

[Skip Fix]

Unless the metering block has a residual pressure valve for the drums in it. If so you still have the pads closer to the rotors if not dragging compared to the fronts.

Some drum master cylinders had the pressure valve built in others had it in the valve.

[Ron Sutton]

There are few different possible causes & cures. But before you go there, the question is ... do you want to decrease the rear braking force ... or increase the front braking force?

Of course, ultimately ... regardless of how much total braking force you end up with ... you will want the braking to be & feel balanced (which means more front braking bias). I assume you bought these brakes to improve the braking performance of your car, from what it had before. But before you work out a cure for your car, ask yourself "Does the car now have massive braking force with the new brakes ... almost too much ... and I can afford to give up some braking force in the rear to balance the braking?"

-or-

"Could the car benefit from more front braking force (to balance with the rear), and therefore end up with more total braking force, to make the car stop even better?"

If you want more front braking force, several knowledgeable folks on this site can offer smart ways to achieve that. And, if you want less rear braking force, they will be offering different suggestions.

Help guide us on what you want. And when you do, include the caliper info (# of pistons & sizes), master cylinder info (dual or twin & piston sizes) along with brake pad compound name. And true rotor diameters front & rear. Other things matter, but probably not for this situation.

[mike63078]

The braking force is not as good as I expected it to be. In fact i think the drums stopped the car better. I feel the car would benefit from more front braking force.

[mike63078]

So I may have a disc/drum master. Could this be causing my issues?

[andrewb70]

So I may have a disc/drum master. Could this be causing my issues?

You need to figure out if the MC you are using has a built in residual valve. If the rear brakes are dusty, that can certainly be a sign that a residual valve is present. What size is the MC? You said you have a vacuum issue. Is the assist working at all?

Andrew

[Ron Sutton]

Mike, I am not knowledgeable on what each manufacturer did with each distribution block. That is a can of worms I don't desire to learn about, but I'll bet Tobin for Kore3 knows. Hopefully he chimes in on this thread.

Usually, the distribution block has residual valves built in. I do not know if some also include any sort of proportioning valving from front to rear.

When I build brake systems ... street or race ... I never use the factory distribution blocks, Typically, street cars need residual valves, so the brake lines keep a micro amount of pressure to the brakes (so you don't have to pump them after long periods of none use. We don't use residual valves in race car brakes (Some people do. We don't). We do use them in all street car applications.

Drum brakes need a 10# residual valve & discs only need 2#. This just keeps your brakes "ready" & consistent. If you remove your distribution block, you will need to add residual vales inline. I do not think you have a residual valve issue, but you may want to reduce them to 2# versions anyway.

You have a bias issue ... meaning, in your case, you have too little front braking force. You need more front braking force. Before I offer any suggestions, I need to know your brake system details front & rear ... specifically ... caliper info (# of pistons & sizes), master cylinder info (dual or twin & piston sizes) along with brake pad compound name. And true rotor diameters front & rear. Other things matter, but probably not for this situation.

[woody80z28]

This may seem like a stupid question, but are the lines hooked up on the master correctly? Some MC's have the front line to the front and rear to rear, while some are the opposite with front to rear and rear to front.

[mike63078]

I bought the signature front and rear kit from the right stuff. Ill check the lines.

[mike63078]

I bought the signature front and rear kit from the right stuff. Ill check the lines.

[Ron Sutton]

Did you figure out your problem & solution?

If so, please share.

[mike63078]

Well I had the incorrect master due to the way I ordered the kits. The right stuff sent out a new master. I plan on installing this weekend. I'll follow up next week.

[Ron Sutton]

Mike, thanks for the update.

Please post after you swap master cylinders ... if it fixed it ... with some details. Thanks !

[mike63078]

Sorry for the delay life got in the way of the car. Finally got the new master and hydro boost on and all is fixed. I would highly recomend these brakes to anyone.