Trailer brakes locking up even with a slight brake application

Hello everyone,

I have a Mac Roadwarrior flatbed trailer 2009, where all the wheels lock up everytime I apply the brakes, no matter the brake force applied (slight, normal or heavy). My Truck is a Western Star 5700XE 2016.
I have pulled the trailer with a different truck, same problem.
The problem started after I had new brake shoes installed (otr 4707q green 23k). I weighed the trailer axles individually and the weight was the same. Brought the trailer to different shops. They all tell me it's this or that but so far none of the parts they replaced have fixed the problem. Trailer has new brakes, new drums, new ABS relay valve, 2 new ABS sensors, and new suspension bushings and still the same problem.

Please help

Thanks
Roman

 

What was the weight? How old is the trailer? 4707 is a Q+, while the standard Q is a 4515. Are you certain they put the right shoes on? Could also have been XEM

 

We ran into same problem running 23K brakes on trailers. Switched to 20K and issue resolved.

 

The Trailer is a 2009. Weight was 3540 lb on back axle and 3480 lb on the front.
The brakes have still the stickers on it OTR4707QGRN. All I know is that this shoes are recomended for flatbed trailers.

 

Did your trailer lock up empty and loaded? Mine does

 

The Trailer is a 2009. Weight was 3540 lb on back axle and 3480 lb on the front.
The brakes have still the stickers on it OTR4707QGRN. All I know is that this shoes are recomended for flatbed trailers.

 

Mainly empty on ABS equipped trailers, both on non-abs trailers. Our trailers are super light empty also. Switching to standard 20K Abex 6008 vs the Abex 685 was cure for most. What brand of ABS on trailer. Had lots of issues with Haldex ABS locking up brakes in 2015 time frame. Haldex sent out engineering level laptop/program to adjust some to pressure settings vs air ride pressure.

 

The trailer is equiped with a Haldex slh-a7.
I don't understand how ABS could cause the wheels to lock up? Shouldn't ABS step in after the sensors detecting a wheel lock up?

 

In our case, it wasn't stopping lock up. The Haldex had roll stability and monitored air bag pressure for trailer weight calculation. The pressure sensors would read off and cause over braking. Sensor was located inside of module, so had to replace whole ABS module if sensor failed. I retrofitted all of those trailers over to Wabco 4S/2M since then.

 

Trailer has the correct brake shoes installed (4707 Q Plus) . I checked today with the trailer manufacturer to be sure.