[mercmad63]

General Motors is in deep trouble,having been building SUV's too long, for a Market that really wants Totota landcruisers and BMW X5's etc.and no one really wants their SUV's any more because of high fuel costs ...So if they are starting to sell new cars and trucks with drums ,it's all the more reason why they should go broke.They are starting to play with peoples safety by being cheap and nasty to score more Corporate dollars for the big boys at the top,who either never drive anyway or own a Maybach....never a Chev.
In the words of out forefathers I say..."BOYCOTT GM! ..".LOL
PS,go to the next thread "pontiac GTO brakes " to see just what problems are there to trap the unwary,someone has stripped the "simple" drum brakes and now has a pile of confusing parts to sort out....

 

[88montecarlols]

...but the reason they went back to drums was $$$ just like always. I bet if it wasn't a federal law some cars would still come with drums in the front. Drums are cheaper...not better. That has never been in question.

True, money is often the root of changes in this industry.

 

[427v8]

Wow, lot of different opinions around here, so here are the facts

drum brakes work well once in a while. If you have a big heavy car with namual brakes drums have that servo action to help you stop. And the do that quite well. They don't cool well though and will fade quickly.

Disk's require more pedal effor to stop, hence the booster.
The do cool better though so in a racing environment with repeated hard stops, the disks cool better since they have a built in fan.

Drum brakes, properly designed work just fine for a daily driver, I still have them on the rear of my 97 Caravan and there is nothing wrong with them, the front disks however suck. So the difference is in the implememtation.
drums also work great on a drag car. They have less drag than disks and only need to work once.

 

[xntrik]

Wow, lot of different opinions around here, so here are the facts

Disk's require more pedal effor to stop, hence the booster.

.

No so.
Fords, like Granada or Maverick, use the same master cylinder on manual and power brakes. I have converted several 60s Falcon, Fairlane, Mustang drum brake cars to Granada manual disk brakes. The manual disks have no greater pedal pressure than the original manual drums using the exact same pedal leverage ratio.

The important thing is to use high grade Wagner Thermoquiet brake pads. Cheapo lifetime guarantee pads from NAPA, AZ etc. have a poor coefficient of friction and DO require substantial pedal effort.

I have dealt with several situations of high pedal pressure with little stopping ability and in every case it was cheapo pads. And in every case, the driver told me, "But they are LIFETIME GUARANTEE pads".

I am constantly amazed how many people cannot comprehend that there is a difference in brake pads.

Personally I would not use NAPA pads if they were free and somebody else did the labor. period.

 

[Chop or not ?]

A fellow fanatic has installed the disc setup from the newer crown vics that are starting to pop up in the "Pick a Parts" bolts right up to the Ford 8 & 9 inch diffs. Just had to weld on a bracket for the E-Brake cable. Personally I think disc's aren't neccesary but they do look better with the newer style mags !

 

[1935 Ford Steve]

Frisco. You don't need residual valves with disc brakes all around. Residual valves hold the line pressure on rear drum brakes. Mine work fine

 

[Frisco]

Frisco. You don't need residual valves with disc brakes all around. Residual valves hold the line pressure on rear drum brakes. Mine work fine

This may be correct IF the master cylinder is mounted well above the wheel cylinders (such as on the firewall). It is not correct when the master cylinder is mounted below the floorboards or below the level of the wheel cylinders. It also may not be correct when using the rear calipers that I have.

In my case I need a 2 psi residual valve for the front calipers.

I have GM rear calipers that have the emergency brake as part of the caliper. I believe they are used on Cadillacs and other GM vehicles. I originally used a 2 psi residual valve on them as well. This would not work as these calipers back off .035-.040 when the pedal is released. This caused the pedal to have to be "pumped" to get enough travel in the rear calipers when the next attempt to apply the brakes occurred. By changing to a 10 psi residual valve on these rear calipers they only backed off about .005, thus correcting the problem of having to "pump" the brakes. If I had not already spent $200 for the two rear calipers, I would have purchased the stock Ford drum brakes for the rear as they would have been a lot less frustrating to get to work properly and in my opinion would work just as well for my vehicle.

 

[1935 Ford Steve]

Frisco. Your correct. My mastercyl is on the firewall I put on the Seville Calipers also but they interferred with the sway bar I installed so I put a drive shaft e brake and S10 calipers which are the same as the Seville without the E brake. Brakes worked fine without residual valve but drive shaft e brake sucked and sway bar gave a rought ride on my roads. I have switched back to Seville brakes lost the sway bar and drive shaft e brake. Must use e brake every time with Seville brakes to keep adjusted properly. Interesting on having to pump twice because pads retract too far. Could be don't have e brake adjusted properly Let you know tomorrow as I am testing tonight.

 

[Frisco]

Must use e brake every time with Seville brakes to keep adjusted properly. Interesting on having to pump twice because pads retract too far. Could be don't have e brake adjusted properly

Yes, I am aware of this condition. According to one brake source (MP BRAKES) the emergency brake lever must be ratcheted to pre-set the pad position when setting up the brakes initially. Also stated that the emergency brake must be used to keep the rear pads adjusted (as you also stated). I ratcheted the lever but the pads always backed off too far. Bad ratcheting mechanism???

I also found the following explanation on this site. I tried it (changed the 2 psi residual to a 10 psi) and it seems to have worked.

Begin quote:

Now the questions about residual pressure valves--

Many of you will already know that the traditional drum brake systems use a valve inside the master cyl that
traps about 10 or 12 lbs pressure in the system when the brakes are not being activated, to prevent fluid drainback
and keep the brakes ready to act. That has worked great for many decades.

Disc brakes do not like that much Residual Pressure in the system because they don't have return springs or an
internal mechanism to retract the piston.
It is widely accepted that 2-4 lbs residual pressure is ideal for conventional disc brake calipers.
It is enough to prevent fluid drainback, and in most cases keep the brake pads in contact with
the rotor, partly to keep the rotor clean, and partly for instant response. For disc brakes it is desirable to
keep the brake pads in contact with the rotors.
Using 10-12 lbs residual pressure will, in most cases, cause the disc brake pads to rub the rotors a bit more
than is wanted.
Conventional wisdom says that for a front-disc/rear-drum car you should use 10-12 lbs residual pressure for
the drums in the rear, and 2-4 lbs for the discs in the front.

OK so far.

Now when you want to add rear disc brakes, which would give you 4 wheel disc brakes, it would seem to
follow that you would want 2-4 lbs residual pressure for both the front brakes and the rear brakes.. right?

NOT SO FAST! Hold your horses!

The "conventional wisdom" that tells you to use a 2-4 lb residual valve for disc brakes doesn't
take into consideration the fact that not all calipers are the same.
The usual front calipers do not have any return springs or other provision to retract the caliper piston
the brake pedal is released. The usual 10-12 lbs residual pressure in a drum brake system is easily overcome
by the drum brake return springs.
Since the usual disc brake caliper does not have the springs, the 10-12 lb residual pressure will keep the
disc brake pads dragging when the brake pedal is released. That is why you need to change to 2-4 lbs
when changing to discs.

SOUNDS GOOD. When using FRONT calipers on the rear without e-brakes, that is OK.

BUT--- What about the Cadillac REAR calipers with the built in e-brakes and internal self-adjusters?

Don't they have return springs, and a retracting mechanism that retracts the piston?
YES.
And that can save you a bit of work.
When you use the Cadillac rear calipers, you will need the 10-12 lbs residual pressure that is
found in the usual drum brake system.
If you follow the conventional wisdom of taking out the 10-12 lb valve and installing a 2-4 lb valve,
you WILL end up with a low brake pedal that will require one or two pumps on the pedal in order to
bring the pedal up to a normal height.

When using the Cadillac rear calipers, you should leave the stock front-disc/rear-drum master cyl alone. I like that situation. It saves a lot of work changing the pressures in the system.

Just use the Cad rear calipers and don't bother changing the stock master cyl and valves.
They are already just right the way they are.
It's when you try to use non-e-brake calipers (front) on the rear that you complicate things.

For a street car- save the extra work, and be legal-- use the recommended Cadillac calipers.

End quote

 

[1935 Ford Steve]

Fresno Probably won't know till the weekend how my rear Seville system will work without residual valve but brake pedal sure feel strong. There are so many variables and opinions. I found that Mr. Godwin @ Godwin Brake (in Street Rodder) was spot on when I set up my brakes years ago with GM front disc and GM 57 rear drums. MP is also good source. Found a good way to bleed my brakes. Took an old cap, drilled a hole in center and added a pressure regulator from my spray gun and attached to air supply. Set to 10 psi and now bleed my brakes in about 5 min. Have to watch fluid level carefully. Used to take an hour with my son who has never forgot the experience.

 

[1935 Ford Steve]

Hey Frisco. Don't know why called you Fresno. I like both places though.

 

[Zmans69Malibu]

Rear disc brake problem

I am pulling my hair out trying to get my rear discs bled. I switched my 69 Malibu over to rear discs and installed a CPP Billet master cyl with built in prop valve. Sent the first one back because I couldn't get any pressure to the rear (front works fine) Got the second (both new) from CPP after waiting almost 2 months, having the same problem not getting any pressure to the rears. Spoke with a tech at CPP and he suggested rotating the caliper so the bleeder valve is on top and bled that way. Still no pressure. No leaks or kinks in the lines. Any similar problems or suggestions out there?

 

[ALASKAN]

Had Same Problem

SORRY

After waiting several months for ccp to help me with anything-and getting bad parts on 2 differant orders or the wrong part altoghter and after being so mislead by their tecs-i went with another system altoghter.

The more i counted on ccp to help me-the more they let me down and still to date 18 months later have never sent me the right parts.

While i like the folks there--there growing buiness and it has gotten huge--has left the customers to suffer-and i used to be a big fan of theirs.

Ifinally went with a elec master cylinder from ABS- american braking systems-and this system has more stopping power then you can ever use-even on my nbig rig and is easy to bleed out.

BEST OF LUCK

 

[T-bucket23]

I am pulling my hair out trying to get my rear discs bled. I switched my 69 Malibu over to rear discs and installed a CPP Billet master cyl with built in prop valve. Sent the first one back because I couldn't get any pressure to the rear (front works fine) Got the second (both new) from CPP after waiting almost 2 months, having the same problem not getting any pressure to the rears. Spoke with a tech at CPP and he suggested rotating the caliper so the bleeder valve is on top and bled that way. Still no pressure. No leaks or kinks in the lines. Any similar problems or suggestions out there?

If the bleeder is not at the highest point in the cylinder while bleeding you will never get a pedal. You must get the bleeder at the highest point. On my t-bucket I have to remove the calipers to accomplish this. you may have to do the same.

 

[Zmans69Malibu]

Brake problem

Thanks, I rotated the rear caliper and had my wife pump it the old fashioned way, finally got some pedal though still mushy. I think I need to put a power booster on it. the car came with manual brakes so I was just going to stay manual with the 4 wheel disc set up . No joy. can't put enough pressure to the discs. It will stop ok but can't get enough pressure to lock the brakes so I know I need more. Guess I'll order the booster in the morning.

 

[Triaged]

The power booster will make it feel much more mushy!

 

[canook2u]

Converting from drum to disc

I'm considering converting my Jeep to rear disc, (Grand Cherokee parts),
but how do you go about deciding what parts to use for older cars, like
' 60s Mopars, or Chevys?
Are there kits, or is it trial and error fitment?
If there are kits, who makes them, are there some better than others?
Thanks,

Fred - The new guy

 

[timothale]

4 wheel disc yes

I just like the feel of a good 4 wheel disc setup... did a little work and helped with the 427 Cobra that set the roadrace track record at MIS...It weighed a little over 2000 pounds... lighter than most rods... Cobra used 2 master cylinders for the brakes with an adjustable balance bar to adjust for front to rear for tires, suspension and weight balance. .. there are double master cylinders kits available and I plan on using one on my 32 roadster, jag front and rear (still a pile of parts in the shop) ... retired Ford engineer

 

[mercmad63]

I find it really amazing that 54 years after disc brakes were found to be the only really effective braking system on a high performance car that people will still insist that rear drums are better.
I too like the feel of discs on a car,even though winding roads are rare here it still gives a feeling of confidence just to be able to negotiate traffic knowing the brakes are going to work well.
Perhaps those who have rear drums don't really have a high performance car or have never used what horsepower they do have.
I know manufacturers like Ford etc still have rear drums on a lot of their products,but that's because they are cheap and their falling sales figures reflect that.

 

[IanRiordan]

I saw a new civic hybrid being pre delivered yesterday, guess what? drums on the rear! I know drums (properly adjusted) have less drag than discs, but if any manufacturer should cop flak over the use of drums in this day and age, it should be honda. Commodores and Falcons have had 4 wheel discs standard since around 1990, yet honda still use drums.
BTW, until 2 years ago M/Benz were using drums on the w168 'A' class.
Not all discs are equal, my stock vs Statesman (with abs) brakes almost as well as my heavier HQ ute with stock Holden front brakes and a disc brake 9 inch out of a 1973 Aussie Ford Landau. The only changes I made to the standard hydraulics were to delete the non return valve from the rear circuit of the master cylinder and, after trial and error, a 1mm shim in the proportioning valve.