Bouncing when unloaded

[leo13]

When I apply my brakes going down the ramp to load the boat the trailer bounces severely when lightly braking. It is a Triton tandem axle trailer with UFP disc brakes on the rear axle. Unfortunately my local ramps are rough with a dozer track finish and long because of the low water levels.

I recently replaced the actuator/solenoid, calipers and bushings. The actuator shock was broken and one wheel/rotor seem to run hotter then the other. It did solve the brake issues but no effect on the bouncing. Any help with finding a solution would be greatly appreciated.

[375VTROCKET]

Sounds like the brakes are trying to lock up when in reverse. Check for a bad connection on the blue wire or a faulty ground wire.

[Bass AHolic]

if it don't do that on a smooooooth surface, its the DOZER tracks, similar to rumble strips

[billnorman1]

If in doubt, mechanically lock out the actuator and see if that stops the bouncing.

[leo13]

I just got a lock out for it before it just had a plastic cover. It only appears to happen when going down hill. It might be the rough finish or the decline. I don't see other trailers doing it at the same severity. It is bad. I have people ask if there is something wrong.

If in doubt, mechanically lock out the actuator and see if that stops the bouncing.

[Mhorberg]

Does the issue happen all the time when you are backing up, or only when you apply the brakes while you are backing up?

Did you have this issue at all before you replaced the actuator / solenoid?

You could have a bad ground going from the trailer to the tow vehicle. Check the wiring at your connectors. The solenoid itself should have a blue wire that connects to the trailer harness, if not connected the trailer will be stubborn to say the least trying to back up.

[billnorman1]

Does the issue happen all the time when you are backing up, or only when you apply the brakes while you are backing up?

Did you have this issue at all before you replaced the actuator / solenoid?

You could have a bad ground going from the trailer to the tow vehicle. Check the wiring at your connectors. The solenoid itself should have a blue wire that connects to the trailer harness, if not connected the trailer will be stubborn to say the least trying to back up.

^^^^^^^^^^^^^^^^^^ This could be a Winner Winner Chicken Dinner!! The ball could be grounding the trailer instead of the white wire, when you go down the ramp it opens the lock out solenoid. What good reasoning Mhorberg

[leo13]

Does not happen when backing only when I'm going down the ramp in the forward direction. Our ramps are so long that we drive down and make a u-turn in front of the water then back up. When I'm driving in the forward direction and I apply the brakes just lightly to slow down to make the u-turn it feels like the trailer is bouncing completely off the ground. Its actually worse because I typically have to ride the brakes lightly on occasion to keep my speed low (5-10mph). I have a newer F150 and it up shifts to the point that there is no engine braking. I guess I could manually down shift and see if engine braking is a solution.

I have a Andersen adjustable ball mount and airbags. I have tried changing the height of the ball mount but have not seen any change. I have it set so the frame of the trailer is level with the ground. I'm thinking about adding shocks if its a feasible retrofit. Not sure if it will help when unloaded.

[Mhorberg]

You may need to adjust the tongue weight at the front of the trailer. You should try and shoot for 10-15% of the total load without overloading the capacity of the coupler. This could also be an issue with the shocks on your tow vehicle. I've seen nothing but problems with the vehicle tow packages that use air-bags when you are using the standard UFP surge brake system.

The first thing that I would try and do is see if you can recreate the problem while using a different tow vehicle, preferably one that does not have any kind of equalized hitch or tow package. You want the trailer to be level with the ground.

You may also have a rotor that has been warped. If you replaced the calipers recently, you may have unknowingly had a damaged rotor as well.

[leo13]

I'm not sure if the tongue weight is an issue since its unloaded when the problem occurs. Loaded it works very well. I have tried so many things to solve this including the air bags. Nothing has made a difference. The tongue weight when loaded is 525lbs. Which is about 13-15%.

I will pull the wheels and check the rotors with a dial indicator. A warped rotor is possible since I replaced the calipers because I did feel one might have been sticking. One wheel/rotor was always warmer and had more brake dust then the other.

You may need to adjust the tongue weight at the front of the trailer. You should try and shoot for 10-15% of the total load without overloading the capacity of the coupler. This could also be an issue with the shocks on your tow vehicle. I've seen nothing but problems with the vehicle tow packages that use air-bags when you are using the standard UFP surge brake system.

The first thing that I would try and do is see if you can recreate the problem while using a different tow vehicle, preferably one that does not have any kind of equalized hitch or tow package. You want the trailer to be level with the ground.

You may also have a rotor that has been warped. If you replaced the calipers recently, you may have unknowingly had a damaged rotor as well.

[fishnfireman]

If you have not already tried it ??? Put lockout key or a washer in front of the brake actuator and see if it still bounces with the brakes disabled.
I have one that bounced some on certain ramps...seems like the steeper and rougher- the more likely it was to start bouncing.
Mine never bounced with the boat loaded...
Just by the way surge brakes work--- once it starts bouncing it will only get worse with each additional bounce. The only way mine would quit was slow way down or stop !!!! GOOD luck !

[leo13]

Thanks for the reply. I have the lock out keys but they would fall out unless taped or banded in so I bought the aluminum lockout knob that replaces the plastic master cylinder cover. I have not had a chance to pull the wheels and check the rotors yet. I will most likely this weekend and will follow up with the results.

If you have not already tried it ??? Put lockout key or a washer in front of the brake actuator and see if it still bounces with the brakes disabled.
I have one that bounced some on certain ramps...seems like the steeper and rougher- the more likely it was to start bouncing.
Mine never bounced with the boat loaded...
Just by the way surge brakes work--- once it starts bouncing it will only get worse with each additional bounce. The only way mine would quit was slow way down or stop !!!! GOOD luck !

[DABS]

I'm not sure the lockout cap will give you the results you are looking for. Once you place it in the Backing position, it will stay there as long as there is force going backward. If the trailer lurches forward slightly, the cap will reset itself back to zero. I would tape the side lockout in place for your test.

[DABS]

It sounds like you have a tandem spring axle. Are your tri rockers on each side equal? What year is this trailer? Are you towing with the tongue level or just above?

[leo13]

I finally had a chance to pull off a wheel to check the rotor runout and it was out .020" with hot spots.

I replaced the UFP actuator with back up solenoid about a year ago because it seemed like the brakes were not working well and it always seemed to have air in the system. I also noticed that one wheel had more brake dust on it and was always warmer then the other. I thought it was because the other caliper had air in it. Should have recognized that their in series and that if one had air they would both function the same. Unfortunately I did not and replaced both calipers. The brakes work good but the bouncing when driving unloaded down the ramp was still very bad.

When I first got the boat I was 2 weeks out from picking up my new truck and friend towed me out to the lake with his older Chevy. It only had a 4 pin connector and I did not think it would cause a problem. I now think the 5th pin was for the back up lights and solenoid. So it might have overheated the brakes made the caliper stick which took out the rotor.


Now I have to replace the rotors and check the back up solenoid. Any how to info would be greatly appreciated. It has the Vault system and I thought it was a 10" rotor but my supplier lists a 9.75" X .75" or 10.25" X .950". It measures .75" thick so I guess its the 9.75. Thanks for all of the help.

[RazorCat]

My tandem BCB trailer bounces some if I back down to load in a hurry. Brakes aren't an issue. Trailer suspensions are stiff. No load and they'll bounce.

[leo13]

In Ca our water levels are so low we drive down and make a u turn in front of the water then back in. It happens when I'm driving forward down the ramp and lightly apply the brakes to slow down. My most local ramp has a rough surface from dozer tread. When it bounces it is so bad that it comes of the ground and people have asked me if I'm angry. Everyone stares. It not just a little bounce. I'm sure if I went a little faster maybe 25-30mph I might be able to flip it up on top of my truck. I think the brakes are locking up because of the warped rotors. Every so often the frequency is timed just right with the bumps and that makes it bounce up violently.

My tandem BCB trailer bounces some if I back down to load in a hurry. Brakes aren't an issue. Trailer suspensions are stiff. No load and they'll bounce.

[DABS]

If it had anything to do with the brakes, you would be able to lock them out and go down the ramp with no brakes and no bounce.

[leo13]

Have not had a chance to try it yet. Partly due to the fact the lake just bottom out and there is not enough water to launch anymore. We are supposed to have a storm next week that might bring it up the ft that is needed. The rotor that was originally running hot is out over .020". The bearings feel good and there is no free play or slop in the hub.

[billnorman1]

The out of true limit on a car rotor is .010, .020 is too much, however earlier I posted that you should check the ground wire on the trailer. It seems the brakes are still ON when you are backing up. This can be caused by grounding through the ball versus the wiring. When you start to back up, the brakes are on if you have a bad ground. This causes the ball to ground the trailer which releases the brakes, only to lose the ground again repeatedly, causing bounce.
Of course I may be wrong, but this could be what's happening.