Front driver side brake locking up on startup

[TimR]

Hi,
Having a bit of a problem with the front driver side brake locking up when I first go to drive. A slight touch of the brakes and the brake locks on hard for a second.
• I’ve had my brakes completely rebuilt (drums all round, new flexible hoses, steel lines, stainless cylinders and stainless master, new brake lines, drums machined, new brake shoes etc.) for about 3 years. No vacuum booster.
• Doesn’t lock up in reverse
• Seem to need to lock up once or twice on bitumen before being completely fine for the rest of the day. Going back and forth in the gravel car park locking up and releasing doesn’t seem to do anything.
• Not losing fluid and brakes have been serviced every year. Haven’t been able to spot any fluid leaks.
The strange thing is that it seems to only happen when the car’s been recently stored outside (gravel car park). Off and on it’s back in a garage and haven’t had a problem at all. Just been serviced again and am having the same problem again.
Bit strange, any ideas? Or recommended brake shops in SE Melbourne to drop it off at?
Thanks in advance!

[Harv]

Could be:
a) crap or a swollen rubber in the slave cylinder stopping it from returning,
b) the adjuster cup on the outside of the slave not wanting to return due to rust or crud,
c) shoe return spring has fallen off,
d) brakes are waaaay over adjusted (too tight),
e) shoe pivot pin is fouled/rusted and preventing shoes pivoting,
f) brake master cylinder check valve is shagged (just had a new one from a reputable supplier fail on the bench ,
g) pedal return spring is not working,
h) pedal fulcrum is sticky.

Some more likely than others.

Cheers,
Harv

[ardiesse]

Tim,

The technical name for this problem is "Holden Morning Sickness". It affects approximately one million early Holdens.

It's largely humidity-related, and is made much worse by the presence of brake lining dust. The linings absorb humidity, and the coefficient of friction increases. The primary (i.e.leading) shoes have articulating links, which gives them "self-servo" action - the braking force on the shoe acts to apply the brake harder. It's a positive feedback thing, and like all positive feedback things it can go out of control: the affected brake locks under light application, and may not release until you reverse the car.

If you are keen, take your front drums off. Sandpaper the linings until they're de-glazed. Brush all the dust out of your brakes and put the drum back on. This will give you a few days' respite. The best preventative though is to drive your car every day.

Out-of-round drums are much more likely to provoke grabbing, as are weak brake shoe retracting springs. Sometimes chamfering the lining at the top of the primary shoe, next to the wheel cylinder, can help (but you need to make a shallow chamfer about 1/2" long the full width of the lining).

But the only practical approach is to learn to live with the problem. When I drive my cars, I don't use the brakes until I get the car out onto the street going downhill. When I've got up to about 20-30 mph, I apply the brakes - very gently at first, and then more firmly as the pedal effort normalises, until the brakes begin to warm up. After the first application, everything's fine. As long as I'm going faster than 20 mph, the brakes don't grab badly, and certainly don't lock up. Walking or running speed is suicidal.

In dry weather, the problem doesn't show up. But now that it's getting to the cool-and-damp season in Sydney, my cars have morning sickness.

Rob

[In the Shed]

Hey Rob,
Yep you can add my FB to the list of Holden's suffering that illness. I wondered whether the drums had a light surface rust which accumulated over a couple days causing (or contributing) to the problem. At first I used to have to drive with my foot on the accelerator whilst lightly applying the brakes. Once that was done they were OK. Winter seemed to be an issue.

Just another idiosyncrasy of early Holdens I guess?

Regards
Stephen

[Errol62]

I’m going to jump in here. I’m rebuilding my stock brakes and wondering what lubricant would be suitable to use on the wheel cylinder adjusting cups. Being concerned about using anything petroleum based for fear of affecting the cup rubbers, I was wondering if lanolin would be suitable. Brakes get hot of course so I had thought high temp bearing grease if not for this issue. I must admit I haven’t consulted the shop manual yet.

Pulling the levers off some old shoes they were pretty well seized, preventing the servo effect described by rob above. Graphite is carbon based so probably a no no. Vaseline is simply deodorised grease and has a low melting point. Don’t want lubricant melting and getting on the linings and drums. Talcum powder??


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[ardiesse]

Clay,

You can use high-temp bearing grease on the threads of the adjusters, but use it sparingly. Or anti-seize compound.
On the cups of the adjusters, rubber grease. You don't want to get petroleum-based compounds anywhere near the hydraulics.

Rob

[Errol62]

Rubber grease, thanks Rob. I knew petroleum was a no no. Don’t want them pesky adjusters seizing. These old brakes need regular adjusting.
Cheers
Clay


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[Craig Allardyce]

Incorrect leading shoe length and leading top edge chamfer. Also get your drum diameters checked and radius grind of the shoes to match. Most mobs don't bother radius grinding shoes anymore and fit way too fat linings which cause the top edge of the leading shoe to pull in when cold.

[ardiesse]

Craig,

What's the appropriate size of the chamfer on the leading edge of the primary lining?
And am I to believe that the linings conform themselves to a hot drum, and so when the brakes cool down the linings contact the drum at the leading and trailing edges first?

Rob

[Craig Allardyce]

Rob I'd say by experience the chamfer should taper down from the top edge to about 1/2" to the material face.

I think there is some merit in your description also. For my part I think it's to do with the drum curvature being different to the shoe lining and the first point of contact is the leading top edge which causes the loc up when it pulles in (self energising). I would think that if the full face or centre of the shoe would be better i.e. if the shoe lining curvature was the same or slightly tighter than the drum. For my mind I think its the shoe being pulled off the wheel cylinder into the drum rather than the shoe sliding on the drum and whilst being pulled down with the direction of rotation.
I have the same problem with my FB RHR wheel. Locks when cold. All good once warm.

I also notice on both cars when the brakes get hot the the front starts to pull to the left. I've done the usual swap and replace routine and both cars have been retubed and new hoses fitted. Return springs have also been replaced. My EK is slightly better but is carrying less weight than the FB. I'm looking at wrapping the front lines especially the left one that is close to the exhaust.

[Harv]

Rob I'd say by experience the chamfer should taper down from the top edge to about 1/2" to the material face.

I learnt a lot from this posting. Have I got the drawing below correct? i.e. the edge that needs to be machined is shown in the red circle, and the machining is as per my dodgy sketch below?

Brakes.png (61.53 KiB) Viewed 1638 times

Cheers,
Harv

[Craig Allardyce]

That's correct Harv. The set up you have shown is what's called a twin leading arrangement if both linings are set high with respect to drum rotation (i.e. one close to the cylinder and one close to the anchor). Also it wouldn't have a fixed bottom anchor. This would allow both shoes to get dragged into the drum but only in one direction. FB/EK are single leading in both directions as both shoe linings are set high (one for forward and one for rearward motion) and it's a fixed bottom anchor. Only one shoe will self energise for each direction of rotation of the drum.
The chamfer you've drawn is right. Radius grind is about getting the diameters of the drum and shoe lining matching.

[Harv]

FB/EK are single leading in both directions as both shoe linings are set high (one for forward and one for rearward motion) and it's a fixed bottom anchor. Only one shoe will self energise for each direction of rotation of the drum.

Because one shoe is leading when going forwards, and the other shoe is leading when in reverse, does this mean that both shoes should be chamfered (ie the edges in both the red and green circles below? Or are only the forward direction leading shoes (red circle) chamfered?

Brakes2.png (56.85 KiB) Viewed 1628 times

I guess for old shoes there is a pretty fair risk of the linings being asbestos bearing, so you wouldn't want to grind them at home. But for new linings (supposedly asbestos free) is there any reason not to grind the chamfer at home? Assuming this would be a hand file type job (or perhaps remove the meat with a grinder then clean up with a file)?

Cheers,
Harv

[Craig Allardyce]

Yes I'd chamfer both shoes harv.

[Errol62]

I’m wondering if they have this the wrong way aroundseems to me that the rear springs need the offset to clear the handbrake transfer rod.


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