ZX Binding drum brake queries

[deian]

Hi people,

Today while adjusting my handbrake, I discovered my nearside rear wheel is binding (even with the handbrake cable slackened a lot), the other side rolls fine, and stops as it should. It takes a quite a bit of effort to move the wheel, it's just about turnable with the wheel off holding two wheel bolts.

Question 1 is, what size is that big nut? Is is a 33 or a 32mm?

What happens if I open that nut, will the cover come off and I can see what's binding the brakes? What is usually the most likely culprit?

Again haynes manual is a bit sketchy, I am not the most clued up on drum brakes.

This nut (see below) looks dodgy, whats happened there, dad reckons it will come off. I can't imagine how it's assemebled, looks like some 'master mechanic' has locked the nut onto the thread/cap (whatever it is) because he didn't have a circlip??



Any ideas and walktroughs for me there??

Thanks

[MikeT]

My recollection of drum brakes is they have two liners that contact the inside surface of the drum. They were often held on by one or two phillips screws (not sure about Cit's though!) as the wheel itself gave the ultimate security.

They may have manual or semi-manual adjusters on the inside face, presenting a small square ended bolt. Turning this moves the liners toward or away from the drum so you might want to back them off before you remove the drum.

[uncle buck]

If I remember correctly the nut is 32mm.....you have to remove the nut to remove the drum.
The nut is a stake nut.....when you have tightened it you bend the outer edge of it into the grove in the axle using a punch & a hammer...this stops the nut coming undone.
You are supposed to renew the nut each time it is removed but what you can do is to use the nut from the drivers side on the passenger side & vice versa, this normally put a fresh part of the nut over the groove in the axle!

If the drum is worn it will be difficult to remove as it will have a ridge in it.... it may come off easily if you give it a bit of persuasion with a hammer, but if not you will have to back off the adjusters to get it off.
You can do this through one of the bolt holes in the drum....shine a torch through the bolt hole & slowly move the drum around until you spot the adjuster....you can then wind it off with the tip of a small flat blade screwdriver, I think you will want to turn it in a downward direction to wind the brake shoes away from the drum....use trial & error here as I can't remember 100% what way you need to turn it.

The binding brake could be that the area of the back plate that the shoes rest on is covered in rust, this will stop the shoes sliding as they should....clean this area up & put a smear of copper grease on it.
The springs that pull the shoes together could be weak & not doing their job properly.
It could also be the handbrake cable...when they get old they sometimes don't release as they should....if you think the cables are past their best now is the time to replace them while you have the drums off.

Regards.

[deian]

Thank you Uncle Buck, I will take those advice on board. I'm sure the haynes manual mentioned a circlip through the nut that stops the bolt, unless i'm thinking of something else.

Anyway, I have a 32mm, i was hoping it wasn't a 33mm as it's a funny size.

Thanks

[jeremy]

I agree with what has been said. The cables are prone to siezing and will probably need replacing. On ours the back cylinders were leaking and the shoes were US. The adjusters were stiff as well.

The adjusters may well respond to very careful cleaning and re-assembly. make sure the thread for the ratchet wheel is clean and greased and that some grease gets under the contact face of the wheel and that when assembled it turns freely and that the strange looking spring and levers work correctly.

I bevelled the ends of the linings, cleaned and sanded the backplate contact areas and breased them. (some paint would have been better)

When assembling make sure the self adjusters really are working before you stake the nuts again. You should be able to hear them click . I think they operate when the footbrake is pressed but can't recall properly.

[uncle buck]

....I'm sure the Haynes manual mentioned a cir-clip....

Re your picture....if you removed the grease you can see around the nut you will see a big circlip....but this is to do with the wheel bearing in the drum, you don't need to touch it to remove the drum, you only need to remove the nut.

I has a similar problem on my ZX with one of the rear brakes binding & it was the handbrake cable, so be prepared to have to renew the cable....I would recommend replacing both cables....if one side has given up the other must be nearing the end of it's life.

[RichardW]

I hate drum brakes... last time I fiddled with ZX rears I ended up with new drums, bearings, nuts, linings, cylinders, pipes AND adjusters and I was lucky I didn't have to fit a new stub axle as some hand fisted git had been there before me and mullered the thread on the N/S axle (how??? it's M20 FFS!!!!).

Note that the hub nuts are pretty tight - you need a good breaker bar to get them off.

As noted most likely the cable is knackered and holding the brakes on, but then the mech will be all rusted / crudded up inside, the shoes will be shot, the cylinders will most likely to be leaking, and the adjusters (if they are even still there!) will refuse to work .... prepare for the worst!!

[deian]

Thanks to you all, I will look at it again next sunday, i don't live with my parents anymore, and my rented accommodation has gravel drive, not good for jacking cars. Plus my dad will be the one with the big breaker bar and arms like a bear

I'll open it up and analyse the situation. I've not done drum brakes before, they've all been discs, hence the questions. I'll get back to you on the final situation.

[deian]

Hi again,

The drum was a bit tight to come off but I persevered and it came off.

The problem seemed to be the pin holding the brake shoe, the pin comes in from the back of the brake unit, through the brake shoe back frame, a spring is on the front side of the shoe, and a metal plate is slipped over the pin and twisted keeping the top of the shoe in contact with the piston.

Because the spring wasn't pushing the shoe in place, the show would not be straight against the drum, hence the catching.

That is what i saw, it all seemed ok otherwise.

[moodle]

Hi,

I have a really annoying problem which I havent been able to solve.

A while back I changed the rear pads on a 2001 HDi 306 Pug, no problems there wound back the piston and wedged in the new pads. Ok, it was a bit stiff to turn but I thought after a couple of miles they would bed in, but they never did.

Instead it seems as though the pads were permantly binding with the disc which I put up with until the current change of pads. When I took the old one out one was at an angle and certainly looked like it had been rubbing over a long period of time.

I replaced the pads again checking everything meticuously and winding back the pistions the their full extent, sloted the small pin into the grove of the disc on both pads - started the engine and pressed the brakes, took up the slack and all was fine, but no ! guess what these bind exactly the same as well.

The only thing I havent checked is the hand brake but pulling it up it travelas a long way before it engages - anyone any ideas


Thanks,

David

[AndersDK]

Hi David -

Is the rear radius arm on this 306 alloy composite ? then chances are that the caliper has been pressed out in an angle to the disc, because of corrosion between caliper and radius arm.
This problem is very well known on many other PSA cars rear disc brakes.

[moodle]

Not sure on that one Anders, will have to take the wheel off and have a look at the radius arm -

Is there a cure for this ? I am suprised its not a factory recall if its to do with brakes

Best,

David