Hi everyone, ever since getting the car back on the road, the rear brakes grab when they are cold and I’m moving at slow speed. Once I get along the road and stop they are fine. I see some posts where the adjustment is to adjust up until the shoes start to grab the drum and then back off 4 clicks. When checking one side tonight it seems they required many more clicks than 4 to get them to grab.
can being unadjusted too much make them grab? When I put it all back together originally I would have adjusted as per the manual. But they have always been a problem.
Hi Tony, I noticed that you recommended backing the adjustment off 4 clicks after it stops the drum moving, however the manual calls for 40 clicks….
40 click is unreasonable and you will have no brakes
Not sure where you saw me say 4 clicks which could be correct if you back off after the brake shoes were adjusted to contact the drum first
My method is to adjust the front brake where you feel the shoes grab the drum from the front of the drum with the tire off
Place the tire on to the brake drum —with two lugs ( very heavy tires and rims )
Now Grab the tire and spin it on the rim until until it spins one complete turn and comes to a stop where you started
Tire on and off the drum —and spinning it until you get the spin right
That is when the adjustment is correct on the front — and only necessary due to the drums being adjusted from the front of the drum which is not the norm -most drums being adjusted from the rear of the cars drum which is much easier ( no tire on and off required )
You cannot spin the rear tires due to the rear end gear connection so I use 3-4 clicks after I adjust the brake shoes to be just contacting the brake drum
I turn the rear tires to get a feel for how the brake adjustment feels and sounds ( can hear the brake shoes on the drum ( car in neutral )
Take the car out for a spin to heat the brakes
When warm —at a stop sign come to a complete stop - come off the brakes and the car should roll slowly forward with no brake binding felt
You need the cars idle to be correct ( cannot be a high idle ) or you will have a problem with the trans torque converter working agains the brakes as you brake to a stop
Having the trans working against your braking is not good for the trans and could cause heat issues with the trans ( not good )
Hope that helps get your brake adjusted correctly
Backing the car up and hitting the brakes - using the self adjusters to do what they do works very well when working correctly —mostly after the first mechanical adjustments needed after a complete brake job replacement
Oh and in another note, is it common to see the pushrods on an able coming out of the slave cylinders like shown in the photo attached?
That was meant to say “angle” not “able”
Have attached pic of the other side which shows the pushrods at more of an angle.
Also attached a photo showing uneven wear on the bottom of one of the trailing shoes.
The pushrods are normal, so long as the 'C' shaped portion of the shoe at the upper anchor is seated, which it looks to be, then this will not cause a problem, assuming the brake shoes are correct.
My concern is at the bottom of the second pic you posted; here's what i see:
Is that a trick of the lighting, or is the drum rubbing there? It looks like the wear pad was brazed flat ( a common repair and a good one, usually) and that maybe it's time to redo it.
I'd check the surface of your backing pads, to make sure they are not grooved. It could be that the shoe is sticking on that pad and pivoting there, which would also explain the lack of wear near the adjuster and heavier wear near the cylinder (wear should be centered on properly arced pads)
I could be reading way too much into this, it's only one pic, but it's worth looking at, if the drum is touching there, the backing plate may be bent, either from brake heat, brazing heat (assuming that's the gold color I think I see), or from prying off drums somewhere in the past 60 years. If the plate is bent, the brakes will apply weirdly and 'rock and lock'.
so long as the upper anchor is seated, it doesn't matter how the pins are situated. The 'dual servo' action of the free floating drum system means that the links must be allowed to pivot up and down as the brakes are applied.
As seen in the reference pic, an upward angle is normal, provided that both shoes are seated on the anchor and not misaligned on the plate.
Hi Mark, i did see this in my manual. I also spoke to a mate of mine who has been a mechanic for 20 years and he agreed with your view that the pushrods being on a angle was normal. Another thing he mentioned was that the leading edge of each shoe should be chamfered. If it is not (which mine aren't) they will catch the brake dust and eventually present with lock up issues.
I am thinking maybe mine have had new shoe material fitted to the old shoe frames.
I will be filing mine down. I see on the pic you shared above, that both ends of the trailing shoe a chamfered but the leading edges of the leading shoe are square.... I will take a look at the rear pic for a comparison.
What I like to do when diagnosing brake issues (any issues) is to read the parts. They will tell you the story every time.
In the one pic you posted of your shoe, i see a few anomalies that would lead me to suspect the backing plate or the hardware.
First off, the wear pattern on your trailing shoe trails off toward the bottom in a strange diagonal way. It would indicate that the diameter of the drum swept surface is greater toward the backing plate than near the wheel. This never happens, drums wear 'bell-mouthed' where the diameter at the open end is greater than the closed end. So that would indicate to me that at least that shoe is not running square relative to the drum, like it's lifting up on that side, maybe only when it applies, or maybe because that side of the backing plate is lifted.
Second, I see evidence of an uneven application at the lower right (Chatter) which would could be from worn hardware or bad adjustment.
Third, I see what looks like a lot of virgin shoe toward the adjuster and none toward the cylinder end. It may be just the photo, I really can't see the top, but if both the primary and the secondary are worn at the top, the adjustment was too loose, which would also cause chattering but not the uneven wear line. If the primary pad doesn't share that pattern, suspect the hardware because the shoe is moving.
The dark streaks are caused by heat, they are basically meaningless, but i'm sure that you will find they line up with a defect in the drum surface.
I'd be looking at the uneven wear, check the backer plate and the condition of the hold down springs first. I'm gonna guess that you have it dialed in for adjustment, so it must be a little deeper. I'd also take off the shoes to test fit them in the drum. the shoes should be a smaller diameter than the drum, it looks that they are. I, too, will always file down all the edges of the friction surface on both shoes and pads.
Hi Mark, have taken the shoes off and with the way they have been wearing, they sit crooked in the drum. So I’m assuming that the backing plate is bent which wouldn’t surprise me. See pic. It’s had a hard life.
so I guess I need to find a good one. Other side is wearing evenly and consistent with the pad contact patch.
The backing plate contact pads are worn too as you suspected.
Thanks a heap.
Your handle on this subject is just amazing
So very glad you got our backs on this site to solve the hard and in this case somewhat unusual circumstances regarding Cliff brake wear
My first experience with the condition of the brake backing plate being an issue — Who knew ?
Just Love learning all I can about repairing these great car no matter how that happens
Thanks Mark, i will check this and report back.