Trailer Bounces When Braking

[markmcfarland]

Have a 13 star and the trailer bounces/surges if i hit the brakes kinda hard. I've had empty trailers do that going down a steep hill empty, but never loaded. Is there some kind of adjustment that can be made?
I realize it's from the brakes engaging/disengaging rapidly.

[mikeg205]

there's air in the line.. most likely..

[CantRepeat]

Are the brakes working on the trailer? If it's bouncing or jumping it would seem like the truck is slowing down but the trailer is not so it tries to pass the truck. Since it cannot do so it starts to hop around??

[X25John]

I think it's a characteristic of Mastercraft trailers. I've had 2 different Mastercrafts that did the same thing. Once it got so bad I couldn't stop and was pushed into an intersection. Luckily everyone around me saw what was happening and got out of my way. I've been told it's the actuator causing the problem. My 15 trailer has a different actuator than previous years. I haven't had any bouncing issues......yet.

[frankster1969]

Are the brakes working on the trailer? If it's bouncing or jumping it would seem like the truck is slowing down but the trailer is not so it tries to pass the truck. Since it cannot do so it starts to hop around??

The man is right, your trailer brakes aren't working right. I would bleed the calibers first, also after you do that make sure the reservoir is full...

[markmcfarland]

The brakes are working. I may have explained the issue wrong. Instead of bouncing it's more like surging, kinda like engaging then releasing. It does this rapidly. If I can slow down gingerly it doesn't do it.
What it seems like is happening is they engage too strongly. It's like the boat pushes forward/engages the brakes which pulls the trailer back, disengages the brakes, then pushes back again etc.

[markmcfarland]

I was wondering if there was any adjustments. If there was I think adjusting it so the brakes don't engage as strongly would help. Or if there was a spring that disengages the brakes, maybe it needed to be stronger to keep from applying so much braking power.
I tow with a 3/4 ton so stopping is not a problem. But I have towed with the brakes disengaged and you can definitely tell a difference and feel the push.

[markmcfarland]

there's air in the line.. most likely..

How do you fix air in the lines. Can you just bleed them or do I need to replace/drain the fluid?

[mikeg205]

How do you fix air in the lines. Can you just bleed them or do I need to replace/drain the fluid?

bleed till no air in the system.. older trailers made a machine gun sound when braking with air in the line..

[phil_edgecumbe]

I had this problem with my 1997 Prostar 205 and Mastercraft trailer. I tried a different size (larger) master cylinder and bleeding the brakes. I came to the conclusion the trailer is too heavy for the override design.

I ended up fitting an electric over hydraulic actuator (Dexter) and inertia sensing controller in the car. No more hammering under brakes and I can manually apply the brakes using the controller if I need to.

[sprj]

Just put a bolt through the tongue to disable the brakes when towing empty. My brakes work great, just too aggressive when the trailer's empty.

[93Prostar190]

If there is no air in the lines, and the fluid is clean.
Then you need to check to make sure the actuator is moving smoothly back into the trailer nose and back out.

It feels like the actuator is not activating or releasing well and smoothly.

By the very design of surge brakes if they are working properly, then the "bucking" you are describing should not occur.

I would ...
1. Bleed lines. Lubricate the pins where the actuator slides into the trailer.
2. Jack trailer and spin wheels by hand and see if by manually pushing the actuator the wheels stop and release promptly. Any dragging by one wheel would be bad.

[markmcfarland]

Thanks guys. The boat is put away for the winter at the lakehouse 2 hours away. So I'll probably have to wait until spring to mess with this. I will definitely bleed the brakes. If that doesn't fix it, I'll probably take to dealer under warranty.

[CantRepeat]

Just put a bolt through the tongue to disable the brakes when towing empty. My brakes work great, just too aggressive when the trailer's empty.

It's happening to him while the boat is loaded on the trailer, not empty. Locking out the brakes with the boat on isn't a good idea.

[bturner2]

OK let's start with this is not a normal MasterCraft trailer thing, it's a surge brake thing and most likely caused by either something out of adjustment, binding or a worn/malfunctioning part. My last 4 MasterCraft trailers have been just fine but they've also been well maintained.

Bucking occurs typically from the system engaging too hard or suddenly which sets up an oscillation of the brakes being applied then released in rapid succession. There are many factors that can cause this and it's seen often with no load on the trailer (and not just a MasterCraft trailers). With load on the trailer this is not a normal occurrence and is not a MasterCraft trailer normal operation design flaw (did it to it from day one? probably not so something's changed, right?).

The quick things to look for are fluid level in the actuator, damaged/pinched lines (I've ran into this on a friends trailer after he used the folding tongue and pinched the line), rusted or binding pivot points.

Start by checking your fluid. Is it full? What color is it? When's the last time it was changed?

If it's not full where is the fluid going?
If it's not clear its contaminated and needs changing.
If it hasn't been changed in three years you should probably consider changing it anyway.

How often do you use the trailer? Where is it stored when not in use? What maintenance have you been doing to the trailer?

If the answers go something like......

I rarely use the trailer as the boat sits on a lift and use it once or twice a month during the summer.
I store it outside in an open storage yard or under the old oak tree in the back yard.
Maintenance? I thought trailers were built to sit outside and were maintenance free.

Then you probably have a maintenance issue caused by lack of use or storage conditions.

That being said if the fluid looked good the next places I'd look at would binding in the actuator and/or the calipers. If the trailer is stored outside or is not used very often there's a good chance you could have a hanging caliper. Pull the calipers and clean/grease the slides. Make sure the lines going to the calipers are in good condition and not cracked, leaking or pinched. Next if you haven't already, bleed the lines to ensure there's no junk or air in the fluid. Inspect the actuator slide pins for anything that could obstruct smooth operation or rust. If you haven't been lubricating this area start now, same with the coupler.

If none of the above have brought you joy the path from here gets less fun as we're looking at the actuator. A bad master cylinder can cause strange problems. A bad shock absorber in the actuator will definitely cause bucking. A shorted or sticking backup solenoid will cause slamming and bucking too. If you're not comfortable working with these components then it's probably easier to mass replace with a new actuator inner sleeve or take it to a professional.

As stated above, if the rig worked well when it was new and is now giving you problems then something has changed. Start with inspections, doing the recommended maintenance schedule items then move on to the more difficult areas within the actuator. Based on the age of the trailer (assuming you bought the trailer new with the boat and the rig we're talking about is the latest one in your profile) the actuator should be fine although newer components can go bad too.

I'm certainly no expert but I have worked on more than a couple these trailers over the years. Once you understand how they're supposed to work the system is not that difficult to work on.

Good luck resolving your issue.