Trailer Sway - The Hull Truth

cjudge · 11-01-2009, 05:38 AM

I have a 2005 1/2 burb with a 2000 Pursuit 2470 center counsel. Trailer sways horrible above 50 MPH. How do I diagnose issue? Only towed it 100 miles home one time. Went back roads at 45 MPH max. Trailer is dual axle surge brakes one axle

crothers · 11-01-2009, 05:50 AM

Start with getting the tongue weight. Use a bathroom scale to start, use a 2x4 lever as needed if the scale pegs(and it should peg a 300lb scale). Not enough tongue weight is a sure ticket to trailer sway at speed. Solution?, if you do not have the stern of the boat loaded with movable ballast (stuff) that can be relocated to the front of the boat or removed, then moving the boat forward on the trailer is desireable. Hopefully the bow stantion of the trailer is movable.
Oh, check FIRST that the tires are aired cold to the max pressure noted on the sidewall.
Only things I can think of. Good luck.

SHAMROCK69 · 11-01-2009, 05:51 AM

Sounds like you don't have enough tongue weight. Look on trailer boats site or the BoatU.S. trailering club site about how to determine tongue weight. Also make sure trailer is level when you tow it.

welder · 11-01-2009, 07:05 AM

Yes , It sounds like the tongue weight is way off, I would also like to know more about the tow vehicle

Tires, gears, power , trans ,total weight of the whole rig [ truck and boat wet ready to fish/play ] we can't use information we don't have.

Guys , the tongue weight might be lite because a 26' boat is just to much for a 1/2 ton burb . There I said it , he aint got enough Truck.

cjudge · 11-01-2009, 07:32 AM

Hull is 3400 lbs, 2 stoke 600, 1000 for trailer 1000 lbs of fuel and gear 6,000 total. 2005 Yukon XL 5.3 motor XLT with autoride Not enough truck ???

welder · 11-01-2009, 07:57 AM

cjudge, you may have enough truck but I suggest you take the WHOLE RIG to a scale house and weight it then you will know what you are pulling FOR REAL .

You will be surprised at what you have .

Now, go find out what your tongue weight is . should be 450 to 500 lbs going buy your #s

FYI, the alloy boat in my sig pic is just over 6K ready to fish going down the HWY and it's a 23 footer, was weighed on FDA certified scales [ 5840lbs with 3/4 tank of fuel and no gear or ice on her ] and Pacific says my hull only weighs 2600lbs.

kerno · 11-01-2009, 09:10 AM

Trailer sway is scary. You think it might be just one section of road, but it is not. It might be OK at 44 mph, but every time you hit 45 it begins to wag.

As everyone has said, the problem is not enough tongue weight. The boat needs to move forward on the trailer, so take the boat to a ramp, move the bow stand forward 6 inches and give it a try. If you can't move the boat forward, you'll have to move the axles rearward.

rayteagarden1 · 11-01-2009, 10:40 AM

I have sway problems above 50 miles per hour when towing my boat trailer with my motorhome, so no freeway driving. The reason is because of the overhang of the motorhome (the distance from the rear wheels to the trailer hitch).

Towing my boat trailer with my LandCruiser is a real pleasure and 70 miles per hour is no problem, I have a 483 pound tongue weight (maximum allowed is 650 pounds), the boat and trailer weigh a total of 3,510 pounds. Towing with the LandCruiser which weighs 5,425 pounds is a real pleasure and one needs to be reminded the trailer is back there.

JEFF6920 · 11-01-2009, 10:55 AM

Tongue weight

cjudge · 11-01-2009, 01:56 PM

Went to scales total rig 12,900 Boat and trailer alone 6700 Tongue weight 120 pounds. Dealer loaded boat so the upper bow ring was below the bow stand roller. Adjusted the boat so the roller is between the 2 bow rings. Much better towing now. Is that the right place ? Will try to post pictures in a little while

gf · 11-01-2009, 02:30 PM

Quote:

Originally Posted by cjudge

Went to scales total rig 12,900 Boat and trailer alone 6700 Tongue weight 120 pounds.

120 pounds was way too little. Tongue weight should be 5-7% of the total, so 335-469 pounds in your case.

bc22 · 11-01-2009, 02:42 PM

a few ideas to better balance your rig:
- make sure the dual axle trailer is riding level on both axles
- as mentioned many times already a proper amount of tongue wt.
- tongue wt can be adjusted by moving the boat forward or backward on trailer and adjusting bow stand, bunks, etc.
- can also move axles on trailer forward or backwards (move back if too little tongue wt.)
- can u post any pics of the rig? if you're a bit reluctant to do the work yourself, a good trailer shop should be able to help you out and adjust things like brake line, wiring, etc.

ATaylor · 11-04-2009, 05:53 PM

Get the tongue weight up significantly - welder has some good advice for you there. If you are still having problems, run a string from your axle hubs up to the ball hitch and make sure your axles are square to the tow.

Glock Diver · 11-15-2009, 05:40 PM

Yep, trailer sway is scary. Just experienced a nasty case of it on Saturday, while pulling my 22' cc on I-75. Had never had it happen before, but I hit about 66mph and the trailer started swaying HARD. (speed limit is 70, most vehicles doing 75+). Had to slow waaay down and take an exit quickly.

Tires were fine. Trailer/boat weight is 6300 lbs, with 330 lbs of tongue weight.

Does the tow vehicle really play a role in trailer sway? Seems like if its going to happen, it will happen regardless of what's pulling it. My vehicle wasn't moving around at all. The boat sure was.

welder · 11-15-2009, 11:58 PM

Glock, you are at about 5% tongue weight, are you pulling a tandem axle trailer ?

Is your trailer level when hooked to the truck and on flat ground ?

Yes the Vehicle has some to do with the equation .

Glock Diver · 11-16-2009, 09:07 AM

Yes on both accounts. The tandem-axle trailer is level with the ground while towing.

What does a heavier tow vehicle do to help prevent trailer sway? My SUV wasn't really moving around, but the trailer was.

welder · 11-16-2009, 12:02 PM

The Tow vehicle usually has a shorter wheel base [ Than the wheel base from your rear axle to the trailer axle ] than the boat.

Any small movement of your steering wheel multiples to the trailer.

But your biggest problem is the weight on the ball or how the trailer is loaded ,IE , put all of your gear and toys in the stern of the boat while towing which can lighten the ball load.

Simple things we learn while pulling our toys around.

And I Respect you for coming here and asking why , some will never ask and then we read about them in the news paper,

Speed safely ,

mike343 · 11-16-2009, 08:45 PM

Cjudge

The guys are right, you need 400# or a little more on he tongue. The only way to do this is to move the boat forward on the trailer or move the axles back on the trailer. Either way, you move the boat forward relative to the wheels. My simplified calculation (basically lazy) but not that far off is that the movement needs to be about nine inches. If you can get close by moving the bow stop try that and see how it behaves. If it's not enough, you will have to move the axles. I tow 5600# behind a Tahoe with 320# TW and it tows like a dream.

Basis of simplified calculation:
Distance from center of wheels to hitch ball is 20 feet.
Boat weight is 5300# (1400 for trailer)
Assume that right now the CG of the boat is 6 inches forward of the wheel center. The boat then contributes about 110 @ to tongue weight. the trailer structure contributes some.
Moving the boat niner inches forward will put another 300# on the tongue.

Hope this helps.