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Auto reverse brakes issue

by argonaut » 26 May 2018, 22:33

OK ... another all day on this ...
All 4 hubs off again, expander clutches lubricated, and auto reverse cams.
Fitted 4 new Bowden cables
4 new cable ends and 4 half shell covers.
Had 2 mates come and check adjustments & setup.

Adjusted exactly as per AL-Ko manual .... same again, brakes fine, hand brake fine ... but When reversing as soon as coupling at end of stroke ( bellows compressed) ... i.e. as soon as I reverse up a slope ... brakes lock on.
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by argonaut » 27 May 2018, 09:29

Tried. Putting 3, 5 and 20mm slack in actuating rod, still same.
After full set up yesterday, 2 thing I notice.

1. Is that when I apply handbrake is is not exactly vertical (90) it is at about 11 o’clock position.
Thinking I may back off brake adjustment by equal amount on all 4 wheels (maybe 2 clicks) and see if that brings it to 90 degrees and test again.
Brakes certainly set correctly ..adjusted until almost locked, and backed off just enough that if you spin wheel .. it will do 1.5 rotations before drag stops it. (AlKo described method)

2. When I reverse and they lock on, looking at compensator, the swivel sections are not remaining in line confirming that auto reverse is not releasing.
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by Cap'n Jack » 27 May 2018, 13:56

So yes I agree, slacken off the brake shoes. I think although Alko say that's how to adjust them, I often find it is very much a matter of feel. I think to tighten them then loosen off with some friction may not be enough release them completely once in reverse.

Also Rick, is the draw shaft bottoming out completely when in reverse? The reason I ask is that once the cam has been operated by reversing its only a small movement and the bottoming out gives the brakes a chance to not bite, if there is more movement in the draw shaft to reach its bottom position then it may override the cam, if you see what I mean.

As I said previously the adjustments are boringly fine. :mrgreen:
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by argonaut » 27 May 2018, 18:06

Slackened off all 4 brakes .. it did put handbrake in fully 90 degree position ... thought it looked promising ... but no, the rear brakes lock on as soon as I reverse up a slope (my drive). ...which is by no means steep.
Double checked, there is around 5mm of play in actuating rod.

Frustrating.
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by Ianfs » 28 May 2018, 06:58

Very frustrating.

Does the draw shaft bottom out/come to the end of it's travel when reversing?

Just a thought, what's it like reversing on a flat surface?
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by argonaut » 28 May 2018, 09:16

On a flat surface it’s OK ...as the hitch starts compressing, but boat starts rolling so hitch does not fully activate rods.
Reversing downhill is fine as boat weight does not push against tow ball.

Uphill the full weight of boat pushes against car so compresses hitch, and fully applies brakes ( same as when they activate in fwd braking)
Obviously if you then push car backwards the shoes should press against cam, tripping into auto-reverse position.

I’m not sure what you mean by bottoming out.

AlKo state to fully extend the coupling, that loosens Bowden cable, after adjusting the brake shoes clearance. These are set by winding out adjuster until shoes bind, then back off slightly, just enough that if you spin the. Wheel, i5 free rotates only 1.5 turns .... i.e. some drag.
You then adjust rod to take all play out of it, thus as soon hitch starts moving backwards it will start pulling Bowden cables.
You check setting of cables /shoes by manually pulling Bowden cable ... from off to aplied is 5+8mm


I have tested set as that ... with more ‘backing off of drums’. And up to 10mm play in actuating rods ...all same result.
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by Ianfs » 30 May 2018, 08:33

Sorry this took so long Rick.

I’m not sure what you mean by bottoming out.


When the draw shaft is fully pushed home it'll reach the end of its travel and go no further i.e. it bottoms out.

Here's my take on what I think might be happening, but I may be way off base. In the last few centimetres of it's travel the brake rod should pull on the brakes. Therefore if the brakes apply too early when the draw shaft is being pushed backwards the cam will reach its potential too early and will release the brake shoes but then as the brakes are pushed that little bit further come back on again.

What I think should happen is that the cam releases the shoes as the draw shaft bottoms out, thus no more brake effort.

The reason I asked whether you get the same effect on the flat is because I was wondering if its possible that when reversing up a slope the two rear wheels take most of the weight and the two front wheels may be off the ground and therefore the shoes may not have enough pressure to release from the drum. Just a wild thought, might be complete rubbish. :)
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by argonaut » 30 May 2018, 10:12

Indespension when asked said that what should happen is brakes apply as soon as rods move .... the instructions say to set rod with no play.
They add that shoes need to come on firm on drum, then the friction forces the trailing shoe to trip the auto-reverse cam.
It will not work if brakes gap set too wide ...
They give 'counter check' that if you manually pull Bowden cables you should have 5-8mm from rest to fully applied.

I have tried things with rods no p[lay, 5mm, 10mmm & 20mm play and shoes correct, tight and loose.

On the flat ... my assumption is that the brakes don't apply if reversing slowly, as not enough pressure on the coupling to 'pull' the rods.

Going up my drive, all weight is on back wheels only and the full weight of laden trailer is pressing against the coupling forcing full braking pressure.


That is theory ... not sure where that takes me next
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by Ianfs » 01 Jun 2018, 11:25

the instructions say to set rod with no play.


This is the bit I don't get, but I'm no expert. With no play this will mean the brakes will apply very early on during the draw shaft travel, but maybe that's what should happen. If the front actuator lever which is attached the clevis pin and brake rod doesn't travel much during draw shaft travel, your trailer brakes may apply during the last few cms of draw shaft travel, which is correct.

Indespension when asked said that what should happen is brakes apply as soon as rods move


Assume you mean the steel threaded rod from the front actuator to the brake equaliser? :)

So that we are on the same page, here's my summary.

1/ Make sure the brake shoe expanders are the right way round.
2/ Adjust the brake shoes so they are just off the drum when towing.
3/ Tighten the brake rod to the front clevis.
4/ Adjust the rod at the equaliser to apply brakes during the last few cms of travel of the draw shaft whatever adjustment it takes to achieve this, i.e. when the draw shaft comes to a stop when pushed in.

Another suggestion, when you are reversing onto your drive are you able to pull forward by about half a metre to release the brakes? I'm thinking the trailing shoe may lock on (which becomes the leading shoe when reversing and the one I think should release).

The only other thing I can think of is that for some reason (and I can't actually think of a reason why) but by not having the front wheels on the ground during a reverse manoeuvre in order they release their brakes, possibly forces the rear wheel shoes to stay on. I think this may be a daft idea but then trailer brakes are a bit archaic.

I would love to come and help to see if we could trouble shoot this together but you're miles away, albeit in a beautiful part of the World. :D
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by argonaut » 01 Jun 2018, 12:23

Ianfs wrote:
the instructions say to set rod with no play.


This is the bit I don't get, but I'm no expert. With no play this will mean the brakes will apply very early on during the draw shaft travel, - Indespension manual and Alko documents state actuating rod should be set with zero play for all modern couplings

Indespension when asked said that what should happen is brakes apply as soon as rods move


Assume you mean the steel threaded rod from the front actuator to the brake equaliser? :) - yes, one documents does add up to 3mm play at coupling end



1/ Make sure the brake shoe expanders are the right way round. - actuators installed so hinge pin is on same side as autoreverse cam - book pic & atual pic attached
2/ Adjust the brake shoes so they are just off the drum when towing. - set to locked, then backed off minimum to give 1.5 turns of wheel before drag stops it when spun
3/ Tighten the brake rod to the front clevis. - done
4/ Adjust the rod at the equaliser to apply brakes during the last few cms of travel of the draw shaft whatever adjustment it takes to achieve this, i.e. when the draw shaft comes to a stop when pushed in. - not sure how to do that and avoid play & sag in rod , but have tried it with a lot of play in rod (via compensator cone nut)

Another suggestion, when you are reversing onto your drive are you able to pull forward by about half a metre to release the brakes?yes I can pull fwd with ease, but as soon as I put it back in reverse it locks again

The only other thing I can think of is that for some reason (and I can't actually think of a reason why) but by not having the front wheels on the ground during a reverse manoeuvre in order they release their brakes, possibly forces the rear wheel shoes to stay on. - it is only rear wheel taking load, at start of the reverse, front wheel don't even touch the ground ...

I would love to come and help to see if we could trouble shoot this together but you're miles away, albeit in a beautiful part of the World. :D
Sure I can't tempt you to come down ? ...... sort trailer, out on the water, BBQ .... could meet 1/2 way, or come down and stay overnight :-)
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