Problems with Sway

[riden]

Tow vehicle is a 3/4 ton long box.

Boat is an older 16 ft Lund fibreglass with a older EZ Loader trailer.

I always thought sway was the result of negative tongue weight. That isn't the problem here.

I don't use an actual boat launch. Sometimes it goes on a little **** eyed. But no rythme or reason to sway.

Sometimes it sways and sometimes it doesn't. I always clear out the gas from the back of the boat.

What else can cause it?

 

[Silvertip]

Re: Problems with Sway

Have you actually weighed the tongue? You might be lighter than you think you are. And its not negative tongue weight. Its too little tongue weight. If you had negative tongue weight the tongue would pop up in the air when uncoupled. You need a minimum of 10% of the rig weight on the tongue. When you put all your stuff in the boat, where you put it can affect tongue weight. Load it all in the rear and the tongue gets light. Low tire pressure can also induce sway. Is the tongue level when coupled to the truck. If it's high, you need to drop it down.

 

[kenmyfam]

Re: Problems with Sway

I am with Silvertip on this one. Weight distribution and tire pressures are critical for successful towing of anything. The 10% tounge weight is also critical within a couple of percent. I have used bathroom scales on a solid platform under the coupling to check for tounge weight. Works for me when I am unsure what I have.

 

[DJ]

Re: Problems with Sway

If the trailer tongue is elevated, your tongiue weight decreases.

I suspect the tongue may be elevated, with a 3/4 ton truck If the trailer does not set level, use a drop hitch on your truck.

 

[riden]

Re: Problems with Sway

I was using a 3 1/4 drop receiver, I use that for my other trailers. For the boat, I use a 6 inch drop(I thought it may be the problem too). Trailer is level, that isn't the problem.

I empty my boat before trailering, never anything in the rear.

I will try to weight the tongue.

Thanks

 

[Silvertip]

Re: Problems with Sway

One last thought here -- if this is an older trailer with coil springs, some of those did not track very well at highway speed. There was just too much going on with the suspension. As wear occurs things can get worse.

 

[kenmyfam]

Re: Problems with Sway

I was using a 3 1/4 drop receiver, I use that for my other trailers. For the boat, I use a 6 inch drop(I thought it may be the problem too). Trailer is level, that isn't the problem.

I empty my boat before trailering, never anything in the rear.

I will try to weight the tongue.

Thanks

May want to try it with some added nose weight and see what happens.

 

[tashasdaddy]

Re: Problems with Sway

tire pressure is a must. inflate to the recommeded pressure. this helps support the side walls, cuts down on heat buildup, and tire blow out. if you run lower pressure the side wall give, (sway) the temperature gets hotter than designed and this cause premature wear and the majority of blow outs.

 

[riden]

Re: Problems with Sway

Tires are in great shape and and pressure is 40 lbs for both.

I do have leaf springs though and they are getting old. Food for thought there.

 

[Silvertip]

Re: Problems with Sway

Are these trailer tires (marked ST-xxx-xx-xx). If they are, they should be inflated to 50 PSI. If they are passenger car tires (Marked P-xxx-xx-xx) that may be part of the problem. The solft sidewalls contribute to sway. Lots of info here about "P" vs "ST" tires, load ratings and inflation pressure.

 

[riden]

Re: Problems with Sway

A good question Silvertip, I will look into it.

On my trailer there is an inflation guide. I have 15 inch tires and the guide says "B" tires should be 35-40 lbs.

I saw a B on a tire so I went with 40.

I will look further, but my guess is they are trailer tires as they have a rounded contour.

Update later.

 

[riden]

Re: Problems with Sway

Ok

They are in fact passenger tires. My spare is a trailer tire.

 

[Silvertip]

Re: Problems with Sway

Those may be bias ply tires and the B you saw (as in B78x15) would indicate a size rather than load range. Trailer tires are typically load range "C" tires so they can carry higher air pressure. Just as a test, replace swap one side or the other with the spare and see if sway changes. If sway is eliminated or at least decreased, it is probably a tire issue. If no change is noticed, I'd go back to the tongue weight and check .

 

[kenmyfam]

Re: Problems with Sway

Personally I would only put on trailer rated tires and not car tires. My guess is that is your problem....or a large part of it.

 

[bruceb58]

Re: Problems with Sway

A B78x13 trailer tire can come in load ranges B, C and D.

http://www.greenball.com/tires/biastrailer.htm

 

[tashasdaddy]

Re: Problems with Sway

i have 3 trailers in the yard right now. each trailer has a different brand , and all the spares are different, 6 brands, amazing. all the tires are marked Trailer, Trail, or marked not to be use a passenger tire. two trailers are c rated, little boat is b rated. so form this i would say trailer tires are marked. had Auto tires on a i/o i restored, worse pulling trailer i ever pulled.. hit a bump and the would screach on the fender, side walls didn't support the boat. and the were over rated for the load.

 

[bassboy1]

Re: Problems with Sway

the difference between car tires and trailer tires is that trailer tires have thicker side walls since they do not need to steer. Car tires have thinner side walls to flex while steering. Otherwise it would just skitter forward instead of turining. Change to trailer tires and see if that fixes the problem