Electric Caravan Brakes - how far should they go?

Submitted: Saturday, Mar 04, 2006 at 12:01
ThreadID: 31409 Views:7925 Replies:4 FollowUps:7
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Just thought that as I'm going away for the weekend that I would repack the van wheel bearings as it's about a year since I've done it and noticed that all 4 magnets are equally worn out and needed replacing. The van is 18 months old and has done about 30,000 km. Is this usual life for the magnets? The shoes are in excellent shape.
I use a Prodigy controller & wonder if this may be the problem.
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Reply By: blown4by - Saturday, Mar 04, 2006 at 12:31

Saturday, Mar 04, 2006 at 12:31
Mmmm! I was not aware the magnets were a wearing item. I thought the linings just wore out the same as any drum brake assembly just that they are actuated differently i.e. Electrically. I will be equally interested as you to hear what the other more knowledgable replies say about this.
AnswerID: 158531

Follow Up By: Darian (SA) - Saturday, Mar 04, 2006 at 18:29

Saturday, Mar 04, 2006 at 18:29
Every time the magnets provide any force, they get an absolute "pasting" from the revolving drum. Turns out that the shoes do most of the braking, but the magnets are still trying to "grab" the drum.
FollowupID: 413073

Reply By: Sparkie C - Saturday, Mar 04, 2006 at 13:28

Saturday, Mar 04, 2006 at 13:28
Normally the magnets should be held clear of the brake drums by a small spring clip on the centre pin of the magnet, these frequently vibrate off and as a result the magnet then rubs on the drum face (It happened to mine also). The clips come with ths replacement magnets. Magnets should not be a wear part IMHO
AnswerID: 158541

Reply By: Derek from Affordable Batteries & Radiators - Saturday, Mar 04, 2006 at 13:28

Saturday, Mar 04, 2006 at 13:28
The electro magnets are spring loaded and will rub up against the drum, they do last a long time and normally look worse than they are. Wash then down and inspect them and replace them if they are near to rubbing into the electro magnetic coil.

The best option when replacing is to buy a kit. I buy in a brake kit which includes the shoes, electro magnet and the backing plate all mounted and ready to go. +- $120.00ea

Regards Derek.
AnswerID: 158542

Follow Up By: Mr Fawlty - Saturday, Mar 04, 2006 at 16:20

Saturday, Mar 04, 2006 at 16:20
Yep... very close to the coil, infact there is a mark indicating wear limit & 2 are just below (front wheels) & 2 are just on the mark. All the clips etc were still in place. The area on the drum where the magnets run was very rough but I put the drums in my lathe and took 5 thou off which made them smoother and true & square to the brake face. I thought they lasted as long as the shoes, obviously not.
FollowupID: 413043

Follow Up By: Flash - Saturday, Mar 04, 2006 at 17:06

Saturday, Mar 04, 2006 at 17:06
"The area on the drum where the magnets run was very rough".....
I'd say perhaps there's your problem???
Every electric brake drum I've seen is very smooth (almost polished) where the magnet rubs.
I don't know why it would be rough ....was it perhaps from rust at some stage, or perhaps from other contamination, dust and dirt maybe.
"Off Road" electric brakes are available, though I'm not sure what the difference is- I'm sure someone here could tell you if you were interested.
FollowupID: 413048

Follow Up By: Max - Sydney - Saturday, Mar 04, 2006 at 17:43

Saturday, Mar 04, 2006 at 17:43
Off road magnets are to prevent what happened to me on the highway between Kununurra and Turkey Creek - the magnets, on an Aussie Swag Camper had bounced around on rough road so much that they had worn on the corners, and one just rolled and locked the whole thing up. It had done about 85,000 km when that happened. I subsequently replaced everything as it was well worn - had been in some feindish country.

The off road magnets have more rigid guidance to prevent the rolling. Should not be the problem in this case.

I think you have another problem. For example, you got the controller set so that the van is doing too much of the braking? I now have a caravan, and know the way the dealer set my controller, the van was hauling backwards every time I touched the brakes. I have got them set neutral now - no feel of the van pushing or pulling when I brake. Alternatively, is there a loose connection so you get intermittent braking - that might make the face rough if they come on and off.

Suggest that you go through the set up instructions on your controller and make sure you have set it carefully. Then, when you have fitted the kit that Derek suggests, check the hubs for run out, and make sure there is nothing funny in the way its set up.

Chances are you have got rid of the problem already by machining the face they run on.

I HATE drum brakes - why oh why does someone not make an electric disk brake??

Hope you sort it out.

FollowupID: 413058

Follow Up By: Member - Craig M (VIC) - Sunday, Mar 05, 2006 at 11:24

Sunday, Mar 05, 2006 at 11:24
Max - notice you had a campertrailer before your van - I have just bought a Southern Cross OffRoad and elected not to get brakes. I'm using a Prado V6 to tow it and fully loaded (including) spare wheels, Jerry cans extra battery etc it weighs 960kg. I'm about to head up to my favourite area - Nthn Flinders ranges, up the Strzlecki to Innamincka. When I'm camping in less remote area's the weight will be more like 750kg. I was told it would safely take in excess of 1 tonne. However I am now having 2nd thoughts about brakes. I am not a maniac driving, and rarely exceed 90 - 100 on a good road and off road much gentler. I also hear lots of stories as above about electric brakes sticking etc.
Would welcome opinions from you or any other readers as to whether or not I should get brakes.

FollowupID: 413179

Follow Up By: Max - Sydney - Sunday, Mar 05, 2006 at 18:31

Sunday, Mar 05, 2006 at 18:31
Craig - My Aussie Swag was over 750 kg empty, so had to have the brakes, but would have had them anyway as they do make sure the car brakes don't over work. Having said that, the trailer would have been about 1 - 1.1 tonnes when the brakes failed on me.

I wired the bits back, and disconnected the brake lead, and drove back from Kununurra to Sydney without trailer brakes. Like you, I drive steadily, use the gears to slow down when I can, the engine is diesel; and I must say did not miss the brakes. Where its reassuring is in heavy traffic (and that starts 250 km out of Sydney) - just knowing I am going to be able to pull up fast if I have to.

In your case, I reckon I would have brakes just to be sure. However, if you have the van already, see how you go on your Flinders trip - check out how well you can pull up and look for brake fade etc on the Prado.

Good luck
FollowupID: 413240

Follow Up By: Sand Man (SA) - Sunday, Mar 05, 2006 at 18:33

Sunday, Mar 05, 2006 at 18:33

Any trailer or van with a gross weight greater than 750kg must be fitted with brakes. Either machanically or electrically orerated.

The weight should be marked on the trailer's compliance plate.

I'm diagonally parked in a parallel Universe!

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FollowupID: 413241

Reply By: Darian (SA) - Saturday, Mar 04, 2006 at 18:33

Saturday, Mar 04, 2006 at 18:33
Recent research with an industry pro suggested about 3mm was all the magnets can go down (there are small wear indicator holes in them - they are quite shallow) - when the holes are gone, you need new magnets at well over a $100 each. 30000k of cruising might be ok, but if there was plenty of braking type work on them with dusty conditions through in, that may well be a good run from the first set.
AnswerID: 158600

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