Brake Drums/disk brakes

[sidevalvepete]

On 12/12/2021 at 8:13 AM, blucarsdn said:

I really wonder if there is any advantage (s) to converting a vintage vehicle brake system to disk brakes in lieu of a properly maintained drum brake system? .........

Apologies for the false start above....

 

I do tend to agree with this sentiment but I acknowledge that I have no experience doing a disc conversion so my opinion will be limited. However, I do know that the Chrysler engineers did a great job of designing these old vehicles to operate very well in their day. A well tuned, maintained vehicle with properly adjusted and functioning brakes will start, cruise and stop no problem at all. But they won't be like a modern car. They were designed and built in a long distant past. Giving one of these old girls discs may make it stop marginally better......and it may not. Also,  this 'upgrade' won't make it go faster, steer better or be anywhere near as safe as a modern car. No power steering. No properly designed and  fitted seat belts and no airbags or energy absorbing collapse zones In it's construction. Certainly, enjoy your rides but remember their limitations. Car safety has come ahead in leaps and bounds in the last decade whereas when I was a child in the 1960s safety still wasn't the responsibility of the car construction industry and ne was vehicles then were no safer than thirty years prior.

 

Treat them for what they are and if you really want to enjoy driving them do what all the old sages on this site repeat time and again. Renew fuel system  - tank, lines and properly refurbished pump and carb. Do the same with complete brake system. And the same with all the wiring. Get to know how to tune and maintain the spark function. Read the manuals, devour the wisdom of the forum and you can't go wrong.

 

Having rambled on with that, I do acknowledge some get their pleasure out of playing around with these old girls and making all sorts of tweaks. To each their own.....of course. It's probably you folks that I learn the most from

[Racer-X-]

On 12/10/2021 at 11:00 AM, Sniper said:

In order to do a gravity bleed your master cylinder has to be about the wheel cylinders, something not applicable to the stock braking system.

 

All drum brake systems do not use proportioning valves and in the case of the residual pressure valve, it's part of the master cylinder in the stock braking system.

You are correct that the stock braking system won't do a gravity bleed.  I keep forgetting that my experience with Elvis isn't anywhere close to a stock braking system.  However, gravity bleed requires the reservoir to be above the wheel cylinders/calipers.  If the reservoir is remotely mounted above the level of the bleed ports at the wheels, then a gravity bleed is possible, even with a master cylinder in the stock location. Still, for most of these cars, a gravity bleed is not easily done.  Pressure bleeding might be an alernative to that, feeding pressurized fluid into the reservoir at the master cylinder.

 

As for the disc vs. drums debate, I'm OK with drums all around for a stock(ish) setup that's mostly driven on city streets or country roads.  Yes, they can fade some in hilly terrain, but if you're using the brakes to hold speed going down a hill, you need to learn how to downshift.  Brakes are for slowing down.  Never use the brakes to hold speed on a grade.

 

If you plan to drive on interstate highways or in environments where you'll be exceeding 50-60mph in traffic, you probably need disc brakes at the front, with the complications that brings.

 

Also, IMO, everybody who drives on public roads needs an upgrade to a dual circuit master cylinder, even if you're running the stock drums on all 4 corners. I wish there was a kit available to mount a dual circuit master cylinder in place of the stock one, along with handling the pedal pivot pin.  Maybe one is available and I just haven't found it yet. Or maybe I need to fab up something for that which is better than "Bubba's" welded in solution.

[Sniper]

1 minute ago, Racer-X- said:

You are correct that the stock braking system won't do a gravity bleed.  I keep forgetting that my experience with Elvis isn't anywhere close to a stock braking system.  However, gravity bleed requires the reservoir to be above the wheel cylinders/calipers.  If the reservoir is remotely mounted above the level of the bleed ports at the wheels, then a gravity bleed is possible, even with a master cylinder in the stock location. Still, for most of these cars, a gravity bleed is not easily done.  Pressure bleeding might be an alternative to that, feeding pressurized fluid into the reservoir at the master cylinder.

You are correct that the reservoir height is key, not so much the M/C.  I was just looking at this as a possible option for the under the floor setup we have.

 

Power Bleeder

 

Not sure if the will fit though.

 

As for a kit for dual reservoir M/C.  Several have used THIS KIT though I read, on this site, there are some issues.  No direct experience though.

 

 

 

 

[soth122003]

Correct me if I am wrong, but aren't most master cylinder reservoirs mounted on the frame rail on the drivers side? If so then can't you jack up the front of the car and do a gravity bleed on the rear brakes and then jack up the rear then bleed the front brakes. Seems you shouldn't have to go to high to do the bleed. Maybe 8-10 inches in front to bleed the rears then maybe 10-15 inches in the rear to bleed the front. Plus if your put the jack stands under the frame won't the wheels lower from suspension drop, lowering the cylinders even more. Just throwing this out there since the reservoir has to be higher than the wheel cylinders though not by much. Let me know what you guys think.

 

Joe Lee

[TodFitch]

2 hours ago, soth122003 said:

Correct me if I am wrong, but aren't most master cylinder reservoirs mounted on the frame rail on the drivers side? If so then can't you jack up the front of the car and do a gravity bleed on the rear brakes and then jack up the rear then bleed the front brakes. Seems you shouldn't have to go to high to do the bleed. Maybe 8-10 inches in front to bleed the rears then maybe 10-15 inches in the rear to bleed the front. Plus if your put the jack stands under the frame won't the wheels lower from suspension drop, lowering the cylinders even more. Just throwing this out there since the reservoir has to be higher than the wheel cylinders though not by much. Let me know what you guys think.

 

Joe Lee

At least for drum brakes, there is a residual pressure valve in the master cylinder. I don’t think that any fluid in the master will get past that into the brake lines unless you pressurize the master in some way, gravity alone will not be enough.

[soth122003]

You're right Tod. I forgot about the valve. I wonder then if the reverse theory would work. Jack up the front of the car and let any air in the line from the back brakes work its way back to the master cylinder over a period of time say a day or two. Shade tree mech theory 101. LOL just wondering.

 

Joe Lee

[Sniper]

Residual pressure valves are one way valves, they stop anything under it's rated pressure from going back the the M/C.  They stop nothing leaving the master cylinder.

 

Gravity bleeding works, if you get the reservoir above the wheel cylinders.  Not sure just jacking the car up will work though

[soth122003]

Feeling funny today. Get the car to San Francisco and park it than chalk it on any hill. Depending on which end you want to bleed Nose down or tail down, crack the bleeder open then have lunch. By the time you get back close the bleeder check the reservoir and you're done. All right solved that problem, now on to world domination.

 

Joe Lee