Boat trailer vibrates in pulses at all speeds

Joined
Jul 25, 2016
Messages
9
Hi all,

My boat trailer is vibrating in pulses (about every second or two) at any speed of travel. It sounds/feels like hitting a rumble strip, but a bit milder.

Here are some details:

Trailer is a light-duty, single axle (1000 lb axle) and loaded with a 1436 Lowe jon with 15hp merc 2 stroke (about 250-300 lbs total weight). Heavier gear is usually in truck bed to keep towing as light as possible. I've made a few 100+ mile trips with this happening and want to make sure everything is safe before towing again.

I had the tires replaced and dont think I had the vibration problem after replacing them, or never noticed. Then I did the following upgrades and something changed:

1. Two new hubs

2. Replaced bunks with rollers, as I fish some hard to launch spots (I don't see how this could change things but maybe).

3. the trailer frame is super light and weak. We discovered that the metal tubing leading to the tongue is just a light duty channel (3 sides) with a wood 2x4 fit into the channel. To reinforce this, we welded two square tube braces, which made the trailer much sturdier (before you could literally twist the tongue while it was hitched). Here is a quick drawing of where we added the braces in case this could have something to do with it (new bracing is colored red)
Untitled drawing (5).jpg Do the tires need to be balanced? Any guidance is greatly appreciated.
Thanks!
 

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NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
Does the vibration get faster/more frequent as speed increases? Yes, start with balancing the tires. Double-check the bearings.Jack up each wheel and see if the wheels turn smoothly and there is no slop in the bearings. Also make sure you have sufficient tongue weight.
 

Alumarine

Captain
Joined
Feb 22, 2005
Messages
3,684
When you jack it up and rotate the wheels also check to see if there is a wobble up and down or sideways.
 

DouglasW

Petty Officer 1st Class
Joined
Apr 20, 2018
Messages
269
All the above. It may be because the trailer frame is stiffer now, you can feel the vibration that was already occurring.
 

harringtondav

Commander
Joined
May 26, 2018
Messages
2,438
Check the axle for alignment. Measure the distance from the exact center of the tongue hitch to the inside of a wheel flange. Repeat on the other side to the same measuring point. If the measurements aren't within 1/16", adjust one side of the axle until the distance is the same.

With the trailer on your hitch you can drop a plumb bob from the center of the hitch ball to mark center.
 

David Young

Chief Petty Officer
Joined
Jul 12, 2015
Messages
485
Have your tires balanced then play around with the air pressure. I have to run mine at 30 psi for the best ride. Any higher than that, my boat bounces around too much.
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
If your trailer is stored for long periods, it's possible your tires are developing flat spots, especially if they aren't inflated properly. Those flat spots may take quite a few miles to straighten out, especially on a lightly loaded trailer in cooler weather.

I would have a good look at the tire sidewall and get the max psi for them. Then inflate to the max and make sure they stay that way to prevent low pressure induced flat spots.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,307
If there is a significant amount of toe-in on the axle, the tires will fight then release then repeat with every revolution
 

Lowlysubaruguy

Chief Petty Officer
Joined
Dec 3, 2012
Messages
514
A simple and accurate test if it shows up. Your boats light might not. Get your boat on a dry smooth piece of concrete like a home garage floor while hooked to the tow rig. Tape a section of newspaper together wide enough to span to the outside of the tires lay them out in front of the tires but two or three rows. You only need to join individual rows not the whole thing And tape them to the floor flat on the outsides only. Slowly pull the trailer straight out while someone watches the paper. If the paper pulls inward or outward it needs alignment. It won’t show minor issues but it will tear the paper or pull it loose if it’s way out. It’s not what you’d call flawless. But it won’t take long to do and won’t cost you but a buck to do. On,y a few alignment shops can work on trailers,

was this there before or after you welded the bracing welding tends to make meter warp and shrink your axle may have shifted?
 

TyeeMan

Master Chief Petty Officer
Joined
Feb 27, 2006
Messages
849
You may not be able to balance a light duty tire like that the rim might not allow it. Find a good tire shop, they might be able help you out.
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
Even if they can just spin the tire up, you'll know if that was your issue...
 

TyeeMan

Master Chief Petty Officer
Joined
Feb 27, 2006
Messages
849
Totally agree with that. It would be nice if they could road force test/ balance that type of tire. Yes it's a small would be inconsequential tire, but if its vibrating your boat etc. to pieces it's a big deal.
 

MTboatguy

Fleet Admiral
Joined
Jul 8, 2010
Messages
8,988
Now a days, they can balance pretty much any wheel, with the clip on weights or the stick on weights, I just finally lost a stick on that has been on my truck since 2008, which is the last time my Dad had tires put on this truck that I inherited. I have had it three years and if it was going to come off, it would have been long gone. My 14' utility boat sits on a trailer with small tires and rims and it has stick on weights as well.
 
Joined
Jul 25, 2016
Messages
9
Thanks for the replies.

I finally got around to checking the trailer out again (holiday and work business, etc.)

1. I first thought that maybe I don't have sufficient tongue weight, as the roller bunks I installed are not long and may take too much weight off the tongue. Yesterday I moved gear up to the front and added some extra weight (I calculated that I need about 80 lbs tongue weight). Took the boat fishing and at first thought the vibration was better, but soon realized it was the same.

2. The tires are new and have not sat for more than a couple weeks without use, so I doubt it is a flat spot or excessive wear.

3. I jacked up each side and there is barely, barely a little play. I suppose even though it is miniscule, it could still be enough to cause the vibration. I know the hubs are supposed to be the right size for the axle (1"), but I guess they are barely too big?

4. Balancing still seems like a good option, so I'll see if my local tire guy can do tires this small.

I guess another question is, how dangerous is it to ride like this? I can buy a new trailer, but I just spend a lot of time setting this one up and really like it besides the vibration. I understand that stuff can shake loose over time and vibration is generally bad...also that even if the amount of play in the hub is teeny tiny, it can still eventually mess up the bearings and/or spindle...how much time I got, doc?

Thanks guys, please let me know if you have any more thoughts.
 

ahicks

Captain
Joined
Sep 16, 2013
Messages
3,957
I doubt a tiny bit of bearing slop is causing your headache. That's not to say it's OK though. Any trailer bearing I've ever seen is tapered, meaning you can easily get rid of any slop by careful adjustment of the bearings when adjusting the axle nut. The correct procedure there is to snug the bearing up lightly using a pair of pliers, then backing it off to the point you can insert the cotter pin.

Your balancing plan plan is a good one. You'll see any wierdness in the shape of that tire at the same time.
 

MRS

Commander
Joined
Jul 10, 2005
Messages
2,555
Have you checked to make sure there are no cracks in the frame any where?
Had a old Willy's panel 4x4 lot of years back thing would sake you like crazy,
tried and checked every thing. One day was jacking it up and saw the crack fixed it.
 
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