IW trailer auto reverse not working

[Guineafowl]

Trying to fix a mate’s twin axle DP stock trailer.

He said the front wheels were locking up when reversing, possibly staying locked as the front tyres had flat spots on them.

I’ve stripped all 4 hubs down, replaced the brake cables, and adjusted everything properly. Nothing seemed amiss with the problem hubs. Drums all good, shoe linings good and not lifting off.

This type, and yes, I’ve checked to make sure everything’s assembled correctly and on the right side:

When I rotate the front hubs forwards (handbrake on), they lock up fine. They will reverse about 16th of a turn then lock up solid. The cable balancer seems to take up slack when I do this, which is odd. Rears work perfectly.

When adjusting the shoes (wedge adjuster) the auto reverse works, ie they lock up forward but will turn backwards fine. It’s something to do with when the cable pulls the brakes on, not the adjuster.

I’ve had the hubs off again on one side, compared the two, both the same. I even took the hardware off and laid it side by side to check. Has anyone seen this before? The only thing I can think of, while writing this, is something to do with the spreader link that the cable pulls on (12 o’clock in the pic). I didn’t compare those.

Cheers

 

[addjunkie]

I had one lock up on me. I noticed that the cam bit that rotates when the cable is pulled has a bit a lip on-them, so if its over rotated they lock.
i think on mine the previous owner had tried to adjust the brakes by over tightening the cable rather than taking up wear correctly.

 

[Justme]

With the hand brake on its supposed to rotate a little backwards & then lock up as the compensator takes up the pressure.
They only auto reverse when the brake force comes from the hitch.

Most cause of it locking up when actually reversing are:-
incorrectly assembled
over adjusted shoes
over adjusted cables
over adjusted rods
drums out of round
unlevel trailer so the tyres dont grip the ground enough to activate the auto reverse especially on loose surfaces


Have you got a copy of the brake service date that specifies adjustments?

The car reversing should not move the rod as far as the hand brake lever does. The hand brake lever moves it further to overcome the auto reverse.

 

[8ob]

Sounds like the damper is shot in the hitch, there should be enough spring/damping at the hitch to avoid everything locking up.

Bob

 

[Migmac]

Sounds like the damper is shot in the hitch, there should be enough spring/damping at the hitch to avoid everything locking up.

Bob

My thoughts too

 

[Guineafowl]

With the hand brake on its supposed to rotate a little backwards & then lock up as the compensator takes up the pressure.
They only auto reverse when the brake force comes from the hitch.

Most cause of it locking up when actually reversing are:-
incorrectly assembled
over adjusted shoes
over adjusted cables
over adjusted rods
drums out of round
unlevel trailer so the tyres dont grip the ground enough to activate the auto reverse especially on loose surfaces


Have you got a copy of the brake service date that specifies adjustments?

The car reversing should not move the rod as far as the hand brake lever does. The hand brake lever moves it further to overcome the auto reverse.

Ah, so they might be ok after the strip and cable replacement. I gave it a quick test drive, unloaded, backing up a hill, and was concerned the problem hadn’t gone away. Odd that the rears seem to auto reverse on the handbrake - I thought this was normal and it was the fronts misbehaving.

The info I got was - check cable has free play, then tighten wedge adjuster while spinning wheel forwards, till it locks up. Back off until just free, then 1/2 turn further. Do all 4 hubs, then adjust compensator to a sensible amount of free play.

8ob, I’ll check the hitch damper too.

 

[m_c]

Hitch damper shouldn't have any effect on the auto-reverse.
Auto-reverse is achieved by the drawtube having a physical stop, so it can only operate the rod/cable a limited amount. The handbrake doesn't have a physical stop, so it can pull the rod/cabled further.

Going by what you've described, the cables/rod has been adjusted up too much.

Stick a bit weight on the trailer, and try reversing it. If it locks up, slacken the rod a bit, and repeat.
Once you can reverse, pull the handbrake on and try reversing to make sure the brakes lock up. If they don't lock up, then tighten the rod a bit.

Some trailers it can be a bit of balancing act to find a suitable adjustment point.

 

[pedrobedro]

Brother in law had a caravan that did this. I bent him a piece of flat bar to drop in to stop it pushing the hitch back when reversing.

 

[Justme]

Ah, so they might be ok after the strip and cable replacement. I gave it a quick test drive, unloaded, backing up a hill, and was concerned the problem hadn’t gone away. Odd that the rears seem to auto reverse on the handbrake - I thought this was normal and it was the fronts misbehaving.

The info I got was - check cable has free play, then tighten wedge adjuster while spinning wheel forwards, till it locks up. Back off until just free, then 1/2 turn further. Do all 4 hubs, then adjust compensator to a sensible amount of free play.

8ob, I’ll check the hitch damper too.

Most people over adjust the free play in the rods / cables.
They get the shoes right but without the slack in the system the vehicle braking pulls the cable into the handbrake compensated range hence no auto reverse.

Some times its also reversing to gently. They can need a push to overcome the fact that they locked up when you stopped.
Its actual reverse rotation that makes them release. If they cant rotate then they cant release.

Lots of car mechanics just dont get how they work.

If auto reverse on handbrake was normal you could never park on a down hill facing up it un hitched.

If you stop gently on the flat. Hand brake on & unhitch then push trailer hard backwards you should see handbrake lever travel further taking up the auto reverse slack. The trailer can move 6"-12" but should not do a full rotation.

The damper being weak should not affect the auto reverse it just makes the brakes come on fast / hard when stopping. They dont reduce full travel just damp it so they apply slower with no thump & hence no sudden locking up / skidding.

 

[Justme]

Ah, so they might be ok after the strip and cable replacement. I gave it a quick test drive, unloaded, backing up a hill, and was concerned the problem hadn’t gone away. Odd that the rears seem to auto reverse on the handbrake - I thought this was normal and it was the fronts misbehaving.

The info I got was - check cable has free play, then tighten wedge adjuster while spinning wheel forwards, till it locks up. Back off until just free, then 1/2 turn further. Do all 4 hubs, then adjust compensator to a sensible amount of free play.

8ob, I’ll check the hitch damper too.

PS
unladen up a hill I would expect issues as you wont be level & grip will be reduced on one axle.

If the tyres cant grip more than the brakes have then it cant auto reverse.

Up hill on grass even with correctly set up brakes is when you want the old U clip to stop them coming on at all.

 

[Guineafowl]

Thanks all - my mistake was trying to use the handbrake to mimic the hitch being pushed in. Of course, it’s on a spring so not realistic.

I’ll let a bit more slack in the rod and give it back to him. It must have seriously locked up at one point, because one tyre has worn right through the wires in one spot