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braking is HARD
https://slantsix.org/forum/viewtopic.php?t=14829		 Page 1 of 2
Author:  oibrownskin [ Wed Oct 26, 2005 12:17 pm ]
Post subject:  braking is HARD
when i first bought my 1966 dodge dart 270, a decent press on the brakes would lock them uip. Since changing the shoes (all of them, all around 9" drums) I have to press the hell out of the pedal to stop at all. THe pedal is not spongy ( i did replace master cylinder, but there are no leaks and i have not lost any fluid). I am thinking that on one or more wheels only one of the two shoes is grabbing. What can I do to ensure both shoes in all drums are working properly?

any tricks to adjust brakes with ease? and without a hand pump to pump and bleed the brake system?

anyhelp is appreciated.

Caesar
Author:  Dennis Weaver [ Wed Oct 26, 2005 12:43 pm ]
Post subject: 
They probably just haven't "broken in" yet... How long's it been?

D/W
Author:  SlantSixDan [ Wed Oct 26, 2005 2:25 pm ]
Post subject:  Re: braking is HARD
Quote:
when i first bought my 1966 dodge dart 270, a decent press on the brakes would lock them up.
Not good. If the brakes will lock up under less than sheer-panic pedal force, it means that either they're not adjusted properly or the linings are contaminated and grabbing.
Quote:
Since changing the shoes (all of them, all around 9" drums) I have to press the hell out of the pedal to stop at all
Very typical with new linings. They're still "green", not yet bedded in or thermally cycled, and they're not making very effective contact with the drums (nobody cam-grinds shoes to fit the drums any more; everyone's afraid of brake dust, so the idea is that you're supposed to bed them in by stopping with them and just do "asbestos" you can that way).

Problem is, it's REALLY easy to glaze the linings and spoil their effectiveness in this early bed-in period. I keep an old toaster-oven in the garage and actually bake the linings before installing them (easier with disc pads than with drum shoes). Not only are thermally uncycled linings much less effective, but new "green" linings will outgas when heated up, and this causes a high-pressure gas layer to come between the friction material and the drum, which makes it very tough to stop. Prebaking greatly shortens the lining bed-in time.

Also, these older brakes were not made with the modern "lifetime" lining compounds in mind. Those compounds work OK in modern cars with vastly boosted brakes, but the less costly ordinary linings work better in nonpower-9" drum systems. (Of course, bigger or disc brakes work much better still, but that wasn't your question.)

Did you turn or replace the drums? What procedure did you use to bleed the brakes? Did you check, rebuild and/or replace any of the wheel cylinders?
Author:  Bohmer2 [ Wed Oct 26, 2005 3:04 pm ]
Post subject: 
Dan,

Questions about baking pads or shoes, are you talking about a basic pop-up toaster oven or a small toaster type oven? If its a small toaster, what temperature do you set it to and how long do you toast them for? Am I correct in assuming you let them cool (back to room temp) before installing them? I assume when you say that this can be done with disc brake pads you are talking about modern pads with older rotars or is this a necessity more because of the characteristics of the caliper, master cylinder, older brake system design in general?

Brain
Author:  SlantSixDan [ Wed Oct 26, 2005 5:14 pm ]
Post subject: 
Quote:
you talking about a basic pop-up toaster oven or a small toaster type oven?
If it has slots in the top and the bread gets put in vertically, and pops up when it's done, it's a toaster.

If it is a small countertop oven that also has "toast" settings, it's a toaster oven (or, properly, "Toast-R-Oven", which was a GE trademark until Black and Decker bought GE's housewares division).

I use the latter type (countertop oven).
Quote:
what temperature do you set it to and how long do you toast them for?
500 degrees, bake until the edges are golden brown, all the cheese is melted and a toothpick inserted in the centre comes out clean ;-)

Seriously, I start at 300 degrees for about 20 minutes, then go up to 500 degrees for half an hour or so. When the toaster oven stops stinking quite so badly of hot brakes, they're done.
Quote:
you let them cool (back to room temp) before installing them?
Naw, man, 3rd-degree burns is FUN! Yeah, I let 'em cool.
Quote:
I assume when you say that this can be done with disc brake pads you are talking about modern pads with older rotars or is this a necessity more because of the characteristics of the caliper, master cylinder, older brake system design in general?
I was referring more to the compact size of disc pads compared to drum shoes. It's easier to fit pads into the toaster oven! This "bake in" procedure is applicable for just about any brake friction material in just about any form. Don't put the rubber brake blocks for your bike in the toaster!
Author:  emsvitil [ Wed Oct 26, 2005 6:25 pm ]
Post subject: 
I do the following for seating pads (and shoes) that I learned from motorcyle pad replacement instructions.......

10 stops 20mph-5mph at about .5g's decceleration

let it cool down

10 stops 40mph-5mph at about .5g's decceleration.

Which is similiar to 'SATISFIED' pads at

http://www.tirerack.com/brakes/tech/tec ... ?techid=85

it does get harder to stop at the end of each of the stopping runs........
Author:  Dennis Weaver [ Wed Oct 26, 2005 6:55 pm ]
Post subject: 
Drum shoes are a bit more challenging to seat than disc pads because the outside diameter of the shoes doesn't quite match the inside diameter of the drum, particularly if it is worn. Like Dan sed, nobody will cam grind shoes anymore, (due to fears when it became apparent that asbestos causes cancer - now brake shoes no longer contain asbestos, so it's kinda moot) seating can be a long process and it can damage the shoes since all the heat is concentrated in certain areas.

D/W
Author:  emsvitil [ Wed Oct 26, 2005 7:06 pm ]
Post subject: 
It took 2000 miles before my shoes acted correctly............... (every once in awhile it had a tendency to pull to one side or the other randomly)
Author:  james longhurst [ Thu Oct 27, 2005 6:23 am ]
Post subject: 
ceasar-
did you have the drums machined like dan mentioned at the end of his first post? if you haven't and the friction surface of the drum is uneven, you'll have a tough time getting much performance from those little 9 inchers at all. if they were machined, were they within the maximum diameter spec stamped on the drum?
what kind of shape are the hoses in? any swelling or cracking? this is an area where you can lose a fair amount of braking pressure. you replaced the master cylinder. added pressure from this could "overwhelm" your old hoses.
like you said, you replaced the master cylinder. is it the same bore size as the one you replaced? this will really affect what's going on at the wheels in terms of braking pressure. you should be able to check this easy enough by looking up under the dash. you should be able to see it. of course you will need your old M/C to compare it to.
as far as bleeding, you did bench bleed the master cylinder first, right? there should have been instructions on this and a set of plastic adapters and hoses for this in the box with the cylinder. some guys like to do this in the car (so the piston doesn't get pushed too far) or with the cylinder clamped in a vise. tap the cyl on the end with a small hammer or screwdriver handle to shake loose any rogue air bubbles. install and top off the M/C. if the rest of the hydraulics are ok and not getting replaced, you may get away with leaving the line(s) loosely installed at the M/C and having a helper slowly press the brake pedal all the way to the floor, then tighten the line and release the pedal. repeat 2-3 times and clean the mess underhood. if the pedal is still low or spongy, bleed at all 4 wheels starting at the farthest point from the M/C. if you replace all the wheel cylinders and/or calipers, i like to fill the M/C and open all the bleeders and let the system gravity bleed. it's messy, but simple. once the air bubbles stop (keep an eye on the M/C level,) close the bleeders and check the pedal stiffness. find your helper and pressure bleed as necessary.
if you have made it to the end of this post, i must say i'm sorry it's so long winded. i added a couple of extra scoops to the coffee maker this morning and i'm a little jittery. :shock: i hope it helps though, it's all stuff that's worked for me in the past.

-james
Author:  Rust collector [ Thu Oct 27, 2005 6:38 am ]
Post subject: 
I use a belt sander to shape the ends of the bands, to fit the drums better.

It works...
Author:  SlantSixDan [ Thu Oct 27, 2005 9:18 am ]
Post subject: 
Quote:
ceasar-
did you have the drums machined like dan mentioned at the end of his first post? if you haven't and the friction surface of the drum is uneven, you'll have a tough time getting much performance from those little 9 inchers at all. if they were machined, were they within the maximum diameter spec stamped on the drum?
Max allowable diameter is 9.060" on anything but '70-'72 drums, 9.090" on the '70-'72 drums.

On any car with 9" drums that I'm actually going to drive (and not upgrade) that needs brakes, I swap on a set of the '70-'72 drums, which are still available. They are heavily finned for cooling, and are much more massive. This gives the marginal 9" drum brake setup a fair amount more safety margin.
Author:  oibrownskin [ Fri Oct 28, 2005 8:58 am ]
Post subject:  more information
I changed the brakes more than 2000 miles ago, and stopping is still a bear. I had to replace one wheel cylinder on the rear passenger side since it was blown and leaking. I dont have ANY other leaks anywhere else in the system. The replacement master cylinder was a stock replacement and appeared to be the same. I bled the system with my dad and there was NO air in the system. The pedal is ROCK solid.

I havent had a chance to inspect the brakes, might not get to it for a while now, my poor slant needs a rebuild BAD.!!! Have some questions about that, but that is another post.

The drums were never machined, although I need to replace the front driver's side. SOme retard at a tire shop neglected to realize that the driver's side lug nuts are threaded the opposite way, and blasted off on my lug nuts with his impact wrench like it was an F-ing tommy gun. So all drums are old, not sure if stock, but old and I have never had them machined.
the hoses appear to be in decent shape. there are no leaks, but they are old and stiff. will inspect further.

dont know what else to say. thanks for the info, keep it coming.

Caesar
Author:  SlantSixDan [ Fri Oct 28, 2005 9:12 am ]
Post subject:  Re: more information
Quote:
The pedal is ROCK solid.
Could just mean you have three seized brake cylinders.
Author:  emsvitil [ Fri Oct 28, 2005 1:46 pm ]
Post subject: 
You'll need some help with this, as I'm going with Dan's siezed idea.........

Check each drum in turn..

Take a drum off, then have someone slowly press the brake pedal.
The wheel cylinders should expand on BOTH sides.

A partially siezed wheel cylinder may have 1 piston siezed, so that only 1 piston expands out.

If the piston that isn't siezed is the wrong one for the direction of wheel rotation, you lose the inherent force multiplication (servo action) of drum brakes (about 5 times) so even though the shoes make contact, you need 5 times the force on the pedal.............


play figure 5 at

http://auto.howstuffworks.com/drum-brake1.htm

Now if the one piston doesn't work, no servo action........
Author:  sandy in BC [ Fri Oct 28, 2005 1:53 pm ]
Post subject: 
Be careful pressing the brake pedal with the drums off,,,,you may end up with "unsiezed" pistons and fluid from here to Indio....
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