Moparts
Drum brakes weak
Posted By: jst19600
Drum brakes weak - 01/10/15 08:54 PM
I have a 70 roadrunner with manual drum brakes.Its never stopped what i would call good.Recently i put on all new brake shoes,hoses,and brake cylinders.The only thing i did not do was have the drums turned.I did scuff them up with some fine sandpaper.Could the drum linings have hardened,glazed so much that they just wont bite anymore?
Posted By: VincentVega
Re: Drum brakes weak - 01/10/15 08:56 PM
Air in the system is always a possibility. But if you're trying to brake glaze, you shouldn't be using anything finer than 80 grit. You should also be very sore afterwards
Posted By: RapidRobert
Re: Drum brakes weak - 01/10/15 09:03 PM
What bore MC? (is the pedal effort normal/travel normal just not enough "grab" at the (4) corners?. when you stand on it do the rears lockup first? What I'd start with is put it up on stands & run it in gear & see how the rears brake then spin the fronts by hand as a helper hits the brakes. That'd at least be a start. Others will chime in/advise further. PS Make SURE you are braked to a standstill before shifting to park etc (the illusion fools you cuz the vehicle ain't moving)
Posted By: jst19600
Re: Drum brakes weak - 01/10/15 09:29 PM
The M/C and all hardware is all stock.Its doesnt pull to one side or the other and all brakes are working.It just wont grab hard.There is no way i could lock up the brakes.If i power brake it with the stock converter it moves very easy,i cant keep it from rolling.
Posted By: RapidRobert
Re: Drum brakes weak - 01/10/15 09:38 PM
Alright, I had that on the stock car & it was a partly crimped line. You might slide a floor jack under the pig & you could get it up & see what you get & it'd be alot faster than stands (do it safely of course) but I'm thinking it might be the MC but I would bleed it out first just cuz it'd be easier than changing it & I'm assuming the pedal does not pump up at all
Posted By: jst19600
Re: Drum brakes weak - 01/10/15 10:04 PM
Peddle is good and solid and doesnt bleed down.
Posted By: VincentVega
Re: Drum brakes weak - 01/10/15 10:20 PM
glazing will certainly reduce braking performance
Posted By: jst19600
Re: Drum brakes weak - 01/10/15 10:36 PM
Should i have all drums turned provided they arent out of tolerence?Is it a necessity to put on new shoes again if i turn the drums?
Posted By: cjs69mope
Re: Drum brakes weak - 01/10/15 11:02 PM
just make sure if you get them cut you take them to a place that does drums all the time .
i have seen places try to just do a fast cut on the drums and call it good .
well that's not good .To rough of finish is bad. The car will take longer to stop as well.
Drums need to done in two steps 1 cut fast clean up and 2 slow finish.
Don't accept any less.
also try adjusting shoes up to where the drum can't be removed easy but still spins with slight drag.
Posted By: RapidRobert
Re: Drum brakes weak - 01/11/15 01:14 AM
Quote:
Should i have all drums turned provided they arent out of tolerence?Is it a necessity to put on new shoes again if i turn the drums?
(1) no not unless the finish ain't right (2) no. No opinion if the drums are too slick right now giveing a coefficeint of friction not adequate enough to stop it. Tho it's gotta be that or the MC I'd think. If so I'd find a shop that does it correctly in the 2 steps as said & a huge plus would be a shop that arcs shoes to fit the drum contour (here it is
$5 a corner for a pair of shoes). You take in your shoes and the drums & not sure if the drums need to be turned just for that. You might call their shop & see what one of their techs has to say
Posted By: Ronnman
Re: Drum brakes weak - 01/11/15 03:19 AM
How about posting some pictures of the brake setup with the drums removed. Sometimes the shoes get swapped front and back as well as the hardware. Additionally, sometimes a groove is worn in the backing plate and restricts the shoes movement. Anyway, post some pics and the forum will give you places to check.
Ron
Posted By: therocks
Re: Drum brakes weak - 01/11/15 05:13 PM
First is what shoes did you use?My kid had a shop do the brakes on the 66 Charger and they were crap because of the linings.I used to run notjing but NAPAs best.Now I run Advanced best.Drums should have been truned at least for a clean up.If they arent bad a 3M rolox disc on a die grinder will clean them up but they must be cleaned real good before install.My ? is whay run drums Unless its a show poodle or rare change to frt discs.You will never look back.Oh yeah I did brakes almost every day for 30 years as a tec.Rocky
Posted By: SportF
Re: Drum brakes weak - 01/11/15 05:28 PM
You need semi metallic brake shoes. They will increase stopping ability a great deal. I had a real hard time finding true semi metallic shoes last summer, and now I can't find them again. But this link does list them, and it is about what I paid for them. It would seem that the normal auto parts store, even for the cheapest to the premium, just don't work for a darn. When you get some true metallic shoes, you will definately notice the difference.
http://brakeperformance.com/brake-shoes/Premium-Brake-Shoes.php
Posted By: Beeware
Re: Drum brakes weak - 01/11/15 06:00 PM
Friend used this company.
http://www.musclecarbrakes.com/bib6572charger.htmlhe bought both fronts and rear setup. His car really stops great for having 4 wheel drums.
Sport F thanks for the link above the semi metallics shoes are what I've been looking for!
Posted By: JohnRR
Re: Drum brakes weak - 01/11/15 06:11 PM
Quote:
Should i have all drums turned provided they arent out of tolerence?Is it a necessity to put on new shoes again if i turn the drums?
Depends on how much you have driven it with the shoes wearing to the uneven surface of your worn drum.
Seriously you should upgrade at least the fronts to discs , the drum brakes never worked that great even when they were new .
Posted By: Mattax
Re: Drum brakes weak - 01/11/15 07:07 PM
Quote:
How about posting some pictures of the brake setup with the drums removed. Sometimes the shoes get swapped front and back as well as the hardware. Additionally, sometimes a groove is worn in the backing plate and restricts the shoes movement. Anyway, post some pics and the forum will give you places to check.
Ron
I agree with this. Pictures would be good. Check for primary and secondary for being swapped. Since you changed wheel cylinders, I assume the whole system was bled thoroughly. Might be worth checking the wheel cyl. diameters just in case something was changed since 1970.
I also agree with RapidRobert on cutting, and not cutting if not needed. If you do resurface on a machine, then the shoes ought to be arced to match. Not many places still do this. Porterfield and Rochester Brake and Clutch are two places that do.
The lining material can also make a huge difference. With drums on all 4, I almost always have preferred semi-metallic, which was getting harding to find at run of the mill parts stores even 20 years ago. You may have to go to Rochester Brake or similar to get what you want.
On most brands, you can get an approximate idea of the friction generated by the lining from the edge code. For all participating manufacturers, this is either ink or impression stamped on the edge of the friction material. EE is fairly typical, FF is better. Lower second letter, such as FE, indicates the friction reduces as the lining gets hot. A lower first letter, such as DE, indicates friction improves as the lining gets hot.
Friction is just one characteristic of the lining material. If you were talking to people in the business of friction materials for racers (like Porterfield or Rochester) you could discuss how 'grabby' and how well they release as well as the amount of modulation available from different linings.
Posted By: RapidRobert
Re: Drum brakes weak - 01/11/15 08:06 PM
Quote:
If i power brake it with the stock converter it moves very easy,i cant keep it from rolling.
I understand drums ain't discs but lets see if we can find out whats fubared. Even power braked the shoes oughta hold it still
Posted By: Mattax
Re: Drum brakes weak - 01/11/15 08:15 PM
Quote:
Quote:
If i power brake it with the stock converter it moves very easy,i cant keep it from rolling.
I understand drums ain't discs but lets see if we can find out whats fubared. Even power braked the shoes oughta hold it still
I agree and based on this we know the problem impacts on or is in the front.
Posted By: Supercuda
Re: Drum brakes weak - 01/11/15 09:33 PM
Let's all fly off on wild tangents.
Are your front brakes properly adjusted? I'll bet no.
If they aren't then nothing else will work properly.
Posted By: jst19600
Re: Drum brakes weak - 01/11/15 11:34 PM
At first yes the front shoes were installed backwards.Once i got the shoes correct it did stop better but i know it can be alot better.Yes i do have cheap Orielly's (Brake Best) brand on it and i never had the drums cut.The brakes are adjusted correctly.The car is rarely driven which doesnt help much.
Posted By: ahy
Re: Drum brakes weak - 01/11/15 11:54 PM
In terms of shoes and linings, it seems like best initial "bite" comes with the cheapest organic linings and second best are the high end pads Rocks recommends. The organics will fade faster with sustained use however.
The mid range pads usually have the least "bite".
Posted By: ghostrider
Re: Drum brakes weak - 01/12/15 07:54 AM
Quote:
Seriously you should upgrade at least the fronts to discs , the drum brakes never worked that great even when they were new .
HUH! The big drum brakes worked great when new, beat the disc in stopping distance and if adjusted properly would do it in a nearly straight line. The disc were better at a straight line stop but the rears could still kick it around and get it squirrelly if you really pushed it. The big advantage to disc brakes has always been their ability to resist fade with repeated stops because they cool more rapidly, drums would heat up and take a longer distance to stop with quick repeat stops.
I'm not talking about the little drums or even the 10 inch front drums but the muscle cars came with the 11 inch front drums in the late 60's.
If his brakes won't hold the car in place then he needs to look at too much pedal travel, too much shoe travel, or not enough pressure like from a bulging brake hose. 
Posted By: jst19600
Re: Drum brakes weak - 03/09/15 08:20 PM
I have replaced all the brake shoes with semi metallic and new wheel cylinders.Still the same.I have it on jack stands and when car is running in gear and brakes applied the rear wheels will slow down but will not stop unless i put it in nuetral.It appears im not getting enough brake pressure to the rear.Do you think there is a restriction in the line or brake line t-block,possibly master cylinder?
Posted By: skicker
Re: Drum brakes weak - 03/09/15 09:23 PM
If you haven't replaced any hoses I would look there next. Especially the rear one as it holds fluid for both rear wheel brakes.
They swell on the inside and restrict any volume from reaching the wheel cylinders.
Adjustment is key to keeping drum brakes working well.
On the rear of mine I usually set the LR until it will hardly spin by hand and then set the RR creeping up on it till I can hardly turn the wheel.
Posted By: jst19600
Re: Drum brakes weak - 03/10/15 12:34 AM
The hoses are all new also.Adjusted to where i can feel and hear the drag when turning.
Posted By: RapidRobert
Re: Drum brakes weak - 03/10/15 04:28 AM
Man after all this I think I'd get one of these & a fitting or two & see exactly what I am getting at the corners. I'm thinking partial blockage (is a bit rare tho) unless a main line had been hit/partly crimped plus th ehoses being new or inadequate MC but didn't you say it was new. Post how it turns out
Posted By: jst19600
Re: Drum brakes weak - 03/10/15 05:06 AM
The master cylinder is the only thing that is not new besides the hard lines.Perhaps its got an internal leak of some kind,it is rather old.I will replace it and see if it helps.
Posted By: kentj340
Re: Drum brakes weak - 03/10/15 07:16 AM
If drum brakes are not re-centered during adjustment, they are not properly adjusted.
"...gradually move the adjuster until you have a good deal of friction on the wheel, but it is still able to turn with some effort. The next step is very important. Either with a helper in the car or by doing it yourself, hit the brake pedal hard a few times. This will re-center the shoes and you will find that a good deal of the friction will be eliminated. Re-adjust the shoes until you achieve slightly less friction than the last time. Re-apply the brake a few times. When the shoes are adjusted properly, the friction against the wheel will not be altered after the brake pedal is (hit hard and re-centered). The adjustment is correct when the shoes rub lightly against the drum..."
From:
http://www.hemmings.com/mus/stories/2006/10/01/hmn_q_and_a1.html
Posted By: Mike P
Re: Drum brakes weak - 03/10/15 02:17 PM
Mattax hit on this and it should probably be expanded a bit.
“….If you do resurface on a machine, then the shoes ought to be arced to match…..”
When new brake shoes are installed, especially on drums that are worn or previously turned, the arc of the shoes is smaller than the arc of the drum. This results in a just a small contact patch between the drum and shoe until the material wears into the arc of the drum. Back when 4 wheel drum brakes were the norm it was not uncommon to hear complaints about poor stopping after a brake job until the car was driven for a few hundred miles.
Posted By: Jack Zupan
Re: Drum brakes weak - 03/10/15 04:16 PM
My first guess would be air in the lines. Sometimes it's hard to bleed all of the air out of the lines and when you replace everything including hoses. You are only out a little time and some brake fluid if it doesn't help.
Posted By: jst19600
Re: Drum brakes weak - 03/10/15 09:23 PM
Will the ol hitting the brakes hard going in reverse help seat the brakes/adjust them where they need to be?
Posted By: JohnH
Re: Drum brakes weak - 03/10/15 09:42 PM
Things that you need to know,, spongy brake, air in the line, Hard pedal with shoes adjusted good, good shoes,, If you have power brake then I would say A bad power brake booster..
Posted By: dogdays
Re: Drum brakes weak - 03/10/15 11:50 PM
Wow, sounds like adjusting the arc of the shoes is a real dark science. It's not.
Take your drum and put a shoe inside it. If the shoe touches in the middle but not on the ends, put it on a flat surface lining side up and hit it in the middle with a dead blow hammer. Check. Repeat until the shoe contacts the drum all the way. If the shoe touches at the ends but not the middle, turn the shoe so it's vertical, then hit on the end. Check. Repeat as necessary.
It's easier than rebuilding a carburetor, only slightly harder than changing a tire.
R.
http://brakeperformance.com/index.php?ad=google&gclid=CLOSs9nF2rgCFS9dQgodziMAjw
Posted By: Challenger 1
Re: Drum brakes weak - 03/11/15 12:15 AM
My
You must machine or replace the drums after the first set of shoes wore out. No 2 ways about it if you want your brakes to work right. You already know that though I bet. You did Nothing by sanding them with sand paper.
Posted By: RapidRobert
Re: Drum brakes weak - 03/11/15 04:25 AM
John dont even think about ending this without posting what it was
Posted By: SomeCarGuy
Re: Drum brakes weak - 03/11/15 06:52 AM
Any local car guys that might give you another set of eyes? Drums work great for general use and this is totally solvable. Don't get discouraged.
Posted By: TJP
Re: Drum brakes weak - 03/12/15 04:41 AM
Quote:
Wow, sounds like adjusting the arc of the shoes is a real dark science. It's not.
Take your drum and put a shoe inside it. If the shoe touches in the middle but not on the ends, put it on a flat surface lining side up and hit it in the middle with a dead blow hammer. Check. Repeat until the shoe contacts the drum all the way. If the shoe touches at the ends but not the middle, turn the shoe so it's vertical, then hit on the end. Check. Repeat as necessary.
R.
http://brakeperformance.com/index.php?ad=google&gclid=CLOSs9nF2rgCFS9dQgodziMAjw
I agree to a point, back in the day, when the drums were turned, the shoes were arced to the drums with a now obsolete machine, ( which I have two of ) OK fast forward 30 or so years and the material used on the linings has been superseded,( IE: improved, NOT!!) several times by cost cutting / substituting materials that work for MOST of the POPULAR applications.
A 4 wheel drum brake car from the 60's does not fit into the category of MOST POPULAR Applications for the suppliers.
The superseding of the material, losing 5 or 10% effectiveness at each revision of which there have been several) now results in a hard pedal with no effect due to , THE material being used (less effective), and the linings not having full contact with the drum
Posted By: jst19600
Re: Drum brakes weak - 03/25/15 07:31 PM
Is there a proportioning valve or is it proportioned through the master cylinder?I put on a new master cylinder this last weekend and I did seat/adjust the brake shoes per the linked article.Took it for a test drive and i have a good hard pedal and it does stop better,but there is no way it would lock up the brakes.I know im still not getting the proper pressure to the rear brakes.
Posted By: RapidRobert
Re: Drum brakes weak - 03/26/15 06:44 AM
Hello John, I'm glad you checked back in.
Posted By: GTX MATT
Re: Drum brakes weak - 03/26/15 07:10 AM
Quote:
Quote:
Wow, sounds like adjusting the arc of the shoes is a real dark science. It's not.
Take your drum and put a shoe inside it. If the shoe touches in the middle but not on the ends, put it on a flat surface lining side up and hit it in the middle with a dead blow hammer. Check. Repeat until the shoe contacts the drum all the way. If the shoe touches at the ends but not the middle, turn the shoe so it's vertical, then hit on the end. Check. Repeat as necessary.
R.
http://brakeperformance.com/index.php?ad=google&gclid=CLOSs9nF2rgCFS9dQgodziMAjw
I agree to a point, back in the day, when the drums were turned, the shoes were arced to the drums with a now obsolete machine, ( which I have two of ) OK fast forward 30 or so years and the material used on the linings has been superseded,( IE: improved, NOT!!) several times by cost cutting / substituting materials that work for MOST of the POPULAR applications.
A 4 wheel drum brake car from the 60's does not fit into the category of MOST POPULAR Applications for the suppliers.
The superseding of the material, losing 5 or 10% effectiveness at each revision of which there have been several) now results in a hard pedal with no effect due to , THE material being used (less effective), and the linings not having full contact with the drum
Like everything else, asbestos was once the magic ingredient.
Drums get a bad rap all the time, but 11 inch Chrysler drums stop pretty well IMO. No its not a modern sports car, but they're ok. 10 inch on the other hand are pretty bad on a B body.