What is this?

Does sit mean that you can not reverse with the trailer on?

Just sounds a bit odd.

trailer brakes work by the weight of the trailer pushing against the car towbar as you slow down, reversing has the same effect,

an auto reverse axle prevents the brakes coming on when the wheels are turning backwards, a non auto reverse axle has a lever you have to get out and lock to stop the brakes coming on.

if that makes sense???.

Ray

[Edited on 12/3/07 by rayward]

As Ray says it relates to the spring loaded nose/hookup on the trailer as this triggers the brakes when driving, but whether it also locks the brakes when trying to reverse or not.

Ned.

how does it work then? is there some machnaism that senses the direction the wheels turn? (or works electrically off the reverse lamp?)

Theres a mechanism that works when u reverse to not allow the brakes to come on. Its a lever on the shoes IIRC.

Otherwise ud never reverse a braked trailer!!

no electrics on my trailer for it, must be something mechanical, it's all in the spring loaded hitch on mine.

Ned.

The auto reverse bit is not in the towy bit, it's in the brake drums. As the wheels turn backwards and the shoes also try to turn backwards, the mechanism inside allows the shoes to 'collapes' inwards. The mechanism is often part of the shoe or shoe carrier.
HTH or confuses even more!!

Owelly seems nearest to the point.

I have been offered a trailer axle 750Kg capacity and it has a sticker on it that says the axle is fitted with auto reverse brakes.

you can turn the drum forwards no problem but when you turn it backwards then it goes about 1/3 of a turn then locks.

Surely this would not allow you to reverse it?

Unless when coupled to the trailer and the hitch a lever pushed something on the brake backplate and frees off the shoes..............????

The drum locks when there is no brake cable etc connected? strange.

Auto reverse is all in the drums as mentioned above. When the brake is not applied, the drum will freely turn either way. When the brake is applied (either by pulling the handbrake half-way or compressing the hitch as when the car slows down) the drum will not turn forwards, but turning backwards is possible (slight resistance but easilly overcome by hand) this is due to one of the shoes being able to slide on its mounting, meaning it doesnt exert any braking force in one direction.
Pulling the handbrake FULLY on will push the brake shoes even further, overcoming the autoreverse feature and locking the drum in both directions.
To test this, use a ratchet strap or similar to compress the hitch. The trailer will not move forwards but should be easilly pushed backwards. Release the hitch and pull the handbrake on fully. The trailer wont move forwards still, and pushing backwards, it will run maybe 1/4 of a turn of the wheels before locking totally.

I only have the option of the axle which is brand new and that has never been fitted to anything before so cant really test it withought the hitch and the trailer frame

If iits locking one direction with no cables, it sounds like something is amiss inside the drums, the shoes are fitted incorrectly or its over-adjusted. Assuming its brand new and not been tampered with, its probably over-adjusted. There should be an adjuster nut or an access hole on the backplate. Try slackening off the shoes and see if you can get it to spin freely both ways.
What make is the axle? Alko, BPW, Knott?

If its new and a good make like above, as long as the price is right, I would buy it as there isnt that much to go wrong.

Taking the drums off if you need to, just pop off the central dust cap and undo the big hub nut. The above brand axles, the nut is tightened to 270nm iirc. Its NOT advised to re-use the old nuts, they must be replaced once removed and are recommended to be replaced every 2 years anyway.
My local motor factors stock replacement nuts for about a quid each, and can get most types of shoes for about £30 per side iirc. Take the old parts with you as there are several variations of sizes for everything for most brands.
Also, look at www.western-towing.co.uk They do a lot of spares for quite cheap (bowden cables in particular) and have a lot of info pages with exploded diagrams.

Phew, I knew working for 4 years in a caravan workshop would come in handy 1 day!