My trailer tires lock up when braking?

Is it a spread axle? Is your ride height adjusted properly? I had a trailer doing that for awhile and it ended up being the ride height on the back axle was too high and carrying most of the weight so it let the front axle skid.

 

You need to remove the axle locks on the rear axle. Those are seriously the worst idea Hendrickson ever had.

The reason the front axle is skidding is because the rear axle isn't coming up off the locks. The front air bags have no air in them, causing light ground pressure and skidding.

Likely a bent leveling valve rod bracket.

Remove that locking system, throw it in the trash, fix whatever is bent on the leveling valve and all will be well.

 

Another thing you need to check as well--make sure the leveling rod has the proper geometry through the FULL TRAVEL of the suspension.

Aftermarket leveling valves can cause this headache because the adjustment rod is too short. When the suspension bottoms out, or has no air, it bends the attachment bracket that bolts to the brake can.

This lowers the ride height, so the next time the axle locks are activated, the suspension won't raise high enough to release them.

In addition, if you ever go through a weigh station that weighs your axles individually, you're going to be in for a surprise. All the weight will be on the rear axle.

 

The first thing is have your Trailer Brakes adjusted, too tight they will lock up and if too loose they will not stop the vehicle.

 

my 2014 4000dx has same problem. checked every thing from brake adjustment to air pressures in bags. ABS modulation valve is the problem I guess. the trailer has 2 abs sensor setup and no sensors on front axle. I am thinking to replace the whole system with 4 sensor - abs .

 

If your having to adjust the brakes with self adjusting slack adjusters then you have other problems and manually adjusting them is a temporary fix at best.
Remove the locks and check ABS. I prefer the 4 sensor abs systems myself but 2 of my 3 trailers have the 2 sensor.

 

axle locks ? can you describe what part is it ?

 

After all the work he did.....maybe he should recheck his brake adjustment?

 

Just so happens I am pulling a brand new trailer that has these things on it. They are locking arms located on the rear axle. When you set the parking brake on the trailer, they flip inward, preventing the suspension from compressing when a forklift goes in and out of the trailer. This system is extremely finicky to ride height and every trailer I've ever pulled that has these, the front tires are always flat spotted.