How to fix oversensitive brakes on Marston Ace trailer?

[SRRC]

The brakes on my 12t Marston Ace grain trailer are hypersensitive, locking up at the slightest touch on the brake pedal when empty.
It doesn't matter which tractor (and my neighbour has exactly the same issue with the same make of tractor and trailer). Adjusting the rams doesn't make any difference, they still whack on and lock up.
Any ideas how to fix this please?
Thanks.

 

[clbarclay]

Sounds like this is just hydraulic brakes, not air breaks which can benefit from a load sensing valve.

Have you inspected the brakes inside the drums?

 

[Dman2]

My new Bailey is the same
Stops that sharp it`s shook the paint off
Thinking of putting a load restrictor in the brake line

 

[Tractortech]

The brakes on my 12t Marston Ace grain trailer are hypersensitive, locking up at the slightest touch on the brake pedal when empty.
It doesn't matter which tractor (and my neighbour has exactly the same issue with the same make of tractor and trailer). Adjusting the rams doesn't make any difference, they still whack on and lock up.
Any ideas how to fix this please?
Thanks.

Now Then..
Assuming that your brakes are hydraulic. The only solution is to fit a load sensing valve. However, that will only work on a trailer with springs..
Try this.........

Hydraulic Brake Load Sensing Kit

 

[JWL]

Years ago when trailer brakes first started appearing on trailers we had a big Fendt that when coupled with a Merrick Loggin trailer was pretty vicious with the foot pedal when empty so we put a restriction valve that had a knob you could turn to alter the restriction. Ok when you remembered to turn it up or down at the appropriate times, loaded or unloaded.
Used to be easier to have an adapter and plug the trailer brake line into a spool, hardly ever used the tractor brakes then.

Disclaimer first........ don't try this at home. The spool braking was quite useful when doing your Carlos Fandango down the long sweeping downhill on the bypass with the tractor out of gear. I was young and foolish and the copper clocked me at a shade over 40mph, at least I could stop when he was waving me into the lay-by. At those speeds putting your foot on the pedal wouldn't have been advisable when it engaged the front axle into 4wd to get the front braking on the front propshaft.
We had a lad on spuds on another farm that did just that, we never did find the front prop

 

[George Mitchell]

An accumulator tee'd into the line might take some of the initial kick out of it

 

[76masseyman]

Take the trailer drums off first, ensure they’re clean inside, shoes in good order, and all free and easy to move. Then adjust them to take up any unnecessary slack. If the cams are travelling too far, that can cause them to grab.

 

[Farmer_Joe]

Our Marston was poor but it was not new as above check what’s going on in drums first

 

[bobk]

The brakes on my 12t Marston Ace grain trailer are hypersensitive, locking up at the slightest touch on the brake pedal when empty.
It doesn't matter which tractor (and my neighbour has exactly the same issue with the same make of tractor and trailer). Adjusting the rams doesn't make any difference, they still whack on and lock up.
Any ideas how to fix this please?
Thanks.

Mine is the same , pulling the pipe out helps

 

[davidroberts30]

The brakes on my 12t Marston Ace grain trailer are hypersensitive, locking up at the slightest touch on the brake pedal when empty.
It doesn't matter which tractor (and my neighbour has exactly the same issue with the same make of tractor and trailer). Adjusting the rams doesn't make any difference, they still whack on and lock up.
Any ideas how to fix this please?
Thanks.

Take a pic of 1 of the brake rams

 

[Lakesdigger]

It's quite simple if the brakes are sized correctly for a loaded trailer and there is no load sensing fitted they will lock up empty. Other than fitting load sensing (trailer would need to have suspension) any mechanical mods will probably end up with a loaded trailer with inadequate braking.

 

[SRRC]

Sounds like this is just hydraulic brakes, not air breaks which can benefit from a load sensing valve.

Have you inspected the brakes inside the drums?

Yes, hydraulic brakes.
Basic simple system with no load sensing.
I thought the tractor brake valve was proportional, i.e. caress the brake pedal and a little bit goes down the brake pipe, stomp on it and full pressure applied.
I'll have a drum off, but it's all pretty new and low mileage, can't think what might be going on.
I'll get a pic of a ram

 

[Chuckie]

Yes, hydraulic brakes.
Basic simple system with no load sensing.
I thought the tractor brake valve was proportional, i.e. caress the brake pedal and a little bit goes down the brake pipe, stomp on it and full pressure applied.
I'll have a drum off, but it's all pretty new and low mileage, can't think what might be going on.
I'll get a pic of a ram

If it hasn't done much, I'd check the adjustment, load the trailer, then plug the brakes in to a spool and have a drive with them on a bit to shine them up and get them good and warm.

 

[76masseyman]

Yes, hydraulic brakes.
Basic simple system with no load sensing.
I thought the tractor brake valve was proportional, i.e. caress the brake pedal and a little bit goes down the brake pipe, stomp on it and full pressure applied.
I'll have a drum off, but it's all pretty new and low mileage, can't think what might be going on.
I'll get a pic of a ram

Correct, and just because it’s new, don’t think for one minute they’re set correct when the axle was assembled. Some of the worst ones I’ve seen were new !!