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Author Topic:   Why does my trailer sway?

grandmufti posted 05-04-2002 08:42 PM ET (US)
Why does my trailer sway when trailering at highway speeds and I get passed by a semi or hit with a gust of wind.Also happens at times when I make a fast lane change.
kingfish posted 05-04-2002 09:33 PM ET (US)
The first thing that is diagnostic of trailer sway is not enough tongue weight. You should calculate gross weight of trailer, boat, moter, gas, the whole enchilada, and endeavor to have close to ten percent of that weight on your hitch. 2000 pounds gross trailered weight = 200 pounds tongue weight on the hitch.
kingfish
Clark Roberts posted 05-05-2002 05:44 AM ET (US)
In addition to Kingfish's great advice above, check that tires are both same (EXACT) size and are aired to max recommended press! Happy Trailerin'... Clark... Spruce Creek Navy
Clark Roberts posted 05-05-2002 05:48 AM ET (US)
Also tires same type (either radial or bias ply).... Bias ply tires have more side wall strength and may be less sway prone. Clark
grandmufti posted 05-05-2002 09:22 AM ET (US)
My tongue weight is 280 lbs on a 3000 lb package.I have bias ply tires that are inflated to max pressure of 50 lbs.Would 20 lbs make that big of a difference on tongue weight.
grandmufti posted 05-05-2002 10:19 AM ET (US)
Just went out and reweighed my tongue on trailer.240 lbs tongue weight.Looks like the repowering to the 115 four stroke changed my pivot weight.
How close to the 10 percent rule must my tongue weight be?I swayed just as much before the repower as I do now.Before repower I had 280 lbs on tongue.Should I bite the bullet and move the axle back on the frame?
jimh posted 05-05-2002 10:30 AM ET (US)
How many axles on the trailer?
Single axle trailers seem more prone to sway.
Jerry Townsend posted 05-05-2002 10:54 AM ET (US)
Grandmufti - your tongue weight is in the ball park - 5 to 10 % on a single axle trailer and 5% on a multi-axle trailer. But going to around 10% doesn't hurt a thing and can help the trailer dynamics. Decreasing the air pressure can help - as it will give you a little more 'gripping' of the road - but don't go to 20 pounds - perhaps in the 30 to 35 pound range. There will not be more friction per se which is dependent on the weight and the coefficient of friction between the rubber and the pavement/concrete.
Also have someone follow you on the road and see if the trailer is tracking straight. An axle that is not square with the trailer will cause the trailer to 'crab' behind the tow vehicle. ------ Jerry/Idaho
jimp posted 05-05-2002 12:19 PM ET (US)
grandmufti -
Just have to say it, don't mean to be insulting.
I assume you're driving straight without swerving from side to side in your lane. And that when semi rigs pass you, you are not unconsciously turning away and then back. Same with lane changes, that you make them smoothly. A wind gust could cause you to over correct. When I trailered my Montauk cross country in 1989, I was hit with severe cross winds in North Dakota, my top speed dropped to 48 mph in order to keep the trailer behind me. I had been able to do the speed limit up until that point (55-65). Also, maybe when you check your rearview mirrors, you're turning slightly in that direction.
JimP
simonmeridew posted 05-05-2002 06:16 PM ET (US)
You might try putting something with a little weight in in in front of the console, like a full cooler etc. On the other hand, make sure you don't have something heavy in the stern that would try to counterbalence the tongue weight.
Also, you don't have one of those trailers with a tilt pin mechanism do you? They always have some "slop" in them which can translate into side to side sway.
Are the spring shackles tight on the axles? and the receiver mechanism on the rear of the truck nice and tight? Just a couple of things to think about.
simonmeridew
grandmufti posted 05-05-2002 10:58 PM ET (US)
I moved my axle back 4.5 inches this afternoon and brought the tongue weight up to 310 lbs.The trailer is a single axle shorlander.
I have had the sway get so bad that I almost lose control of the Van.The only way it goes away is to slow down fast.I will try towing with the 10% tongue weight and see how it handles.Only time will tell as the conditions need to be right to get it to sway.I don't relly want to induce it by jerking the steering wheel.Will keep you posted.Thanks for the advice.
triblet posted 05-05-2002 11:34 PM ET (US)
I have a single axle Shorland'r, a bit
smaller (Montauk, about 2000 pounds). My
tongue weight is around 100 pounds. No sway
unless I do something abrubt.
Have you checked the wheel bearings?
sklein posted 05-06-2002 08:34 PM ET (US)
Buy a pickup with Quadrasteer (Four wheel steering). It's now available on the GMC Sierra and Chevy Silverado. It does great things for towing, especially reducing trailer sway at high speeds.
http://www.delphi.com/automotive/handling/steering/quadrasteer/
Check out the section on trailering.
Steve
simonmeridew posted 05-06-2002 10:00 PM ET (US)
I've been thinking about this thread for a day now.
I have towed everything from a 300 lb woodsplitter, a 12 foot aluminum boat, to my Montauk 5000+ miles, a 5500 lb GVW including trailer SeaCraft 2000 miles, utility trailers with 3500 lb of gravel, utility trailer with 1000 board feet of green lumber with serious negative tongue weight issues, 6000 lb excavators on a tandem flatbed, all with either a Tundra or formerly a Bronco. By the way I'm not recommending the excavator stunt, or the negative tongue weight, it was only by "personal necessity". I'm sure that many on this forum have ten times the towing experience that I have. Without trying to put words in anyone else's mouth, i.e.: my own opinion only:
If you have a trailer that sways or in any other way is unstable, or you even think might be unstable, there is something seriously wrong with the setup and you are only asking for a situation which you are not in control of your vehicle and could lead to at the least undergarment soiling and perhaps loss of vehicle or boat or life.
Go to a truck scale or gravel scale and take your time to get an accurate weight of all components, including tongue and axle weight. It sounds like you are on the right track with shifting the axle. But maybe your van is not quite the best towing vehicle, due to suseptability(sp??) to crosswinds and light rear end itself. What about vehicle GVW specs? Should you really be putting your boat on a single axle, or would a tandem be better?
If the trailer is set up right you keep having to keep looking in the rear view mirror to see if the trailer is still back there, you can't even feel it.
Just my opinion
simonmeridew
grandmufti posted 05-06-2002 10:51 PM ET (US)

The new truck is out of the question as I tow with an all wheel drive 2000 Astro van with factory trailering package.Besides the van doesn't sway the trailer does.The van is rated to tow 5800lbs. I agree that a tandem axle trailer would be better for towing all the way around.But I have used this trailer for 13 years and am quite attached to it.Most of my tows are under 10 miles on city streets but the occassional 75 mile trip to the islands at highway speed are a little scary at times.
I am a patient man and will work this thru one step at a time.My first step was to add tongue weight which needs to be tested.But I like the suggestion to get the whole outfit weighed so I will know for sure what weight I am dealing with.If it does not rain I will do it tomorrow.If after getting the tongue weight to 10% I still sway I will seek professional help on this forum.
Remember I have short arms and deep pockets so if I can fix it for free or almost free I won't have to see if I can reach the bottom of my pockets.
triblet posted 05-06-2002 11:12 PM ET (US)
Quadrasteer, huh. Reminds me of my high
school buddy Gary Stiles. He was into the
old turtle SAABs, (three cylinders,
two-stroke, pre-mix) and had several in his
back yard. One day he cut the steering out
of one and welded it into the back of
another. He rigged up a shovel handle
between the seats for a tiller for the
rear wheels. He could drive down the road
crabbed about 45 degrees to the line of
travel, and parallel park it instantly in the
tiniest of spots. I think he single-handedly
increased attendance at AA meetings about
25%.
;-)
Chuck
grandmufti posted 05-07-2002 11:38 AM ET (US)
Things I have learned today!My boat and trailer weigh 3800lbs not the 2800-3000 I had estimated by adding up the components.My tongue weight is 300 lbs not what my bathroom scale said.
This means I must add back the leaf I removed from the springs to soften the ride 5 years ago when I replaced them.I think I will be Ok with the 300 lbs on the tongue as the test ride on the freeway went pretty well.I induced a good sway at 65 mph by jerking the steering wheel and the boat straightened itself after about 4 or 5 sways.Before I added more tongue weight the sway would have kept getting worse until I hit the brakes and slowed down.
All these years I sat smug thinking I had the 10% tongue weight on my rig.I never knew I was towing that much weight.If you take anything from this post GET YOUR RIG WEIGHED you carry more junk than you realize.Never assume anything.
The man at the building supply yard did not charge me for the weigh when I explained what i was trying to accomplish.Looks like I may have fixed it for free and will not have to try and get my short arms into my deep pockets.
JimU posted 05-07-2002 12:03 PM ET (US)
you might want to take your trailer to a trailer specialist and have alignment, springs, Hangers and hanger bolts checked for wear and loosness. JIM
grandmufti posted 05-07-2002 12:20 PM ET (US)
I am the trailer specialist.Eveything is tight and aligned.Although I will probably replace the springs this summer for preventive maintenance.I had a set break on another boat and have been running scared ever since.They do wear out and develope stress cracks over time.
grandmufti posted 05-07-2002 12:24 PM ET (US)
No offense to you Jim but I have found if you want something done right you have to do it yourself.Too many neer do wells out there.
jimh posted 05-07-2002 03:27 PM ET (US)
Would temporarily adding some weight to the tongue (so as to increase the tongue weight) be a valid test of how the trailer would behave if the boat were move forward (which would increase the tongue weight)?
whalerron posted 05-08-2002 12:27 AM ET (US)
I stumbled across this tonight. This is a very harsh example of the results of fishtailing...
http://www.boatus.com/Seaworthy/13.htm
Dr T posted 05-09-2002 09:44 AM ET (US)
JimH,
I believe so, expecially if placed on the tongue behind the winch and under the bow.
tds
Jerry Townsend posted 05-09-2002 11:18 AM ET (US)
Jimh - That would give a valid test. Now, strictly speaking - the dynamics of a trailer is dependent on the location of the C/G of the load. As such, the test C/G should be close to the C/G should the boat be moved on the trailer - however, a small weight close to the hitch will have more effect on the hitch load and will not displace the C/G of the resultant trailer load all that much. Therefore - in my mind, your suggestion is good. ---- Jerry/Idaho

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Author	Topic: Why does my trailer sway?
grandmufti	posted 05-04-2002 08:42 PM ET (US) Why does my trailer sway when trailering at highway speeds and I get passed by a semi or hit with a gust of wind.Also happens at times when I make a fast lane change.
kingfish	posted 05-04-2002 09:33 PM ET (US) The first thing that is diagnostic of trailer sway is not enough tongue weight. You should calculate gross weight of trailer, boat, moter, gas, the whole enchilada, and endeavor to have close to ten percent of that weight on your hitch. 2000 pounds gross trailered weight = 200 pounds tongue weight on the hitch. kingfish
Clark Roberts	posted 05-05-2002 05:44 AM ET (US) In addition to Kingfish's great advice above, check that tires are both same (EXACT) size and are aired to max recommended press! Happy Trailerin'... Clark... Spruce Creek Navy
Clark Roberts	posted 05-05-2002 05:48 AM ET (US) Also tires same type (either radial or bias ply).... Bias ply tires have more side wall strength and may be less sway prone. Clark
grandmufti	posted 05-05-2002 09:22 AM ET (US) My tongue weight is 280 lbs on a 3000 lb package.I have bias ply tires that are inflated to max pressure of 50 lbs.Would 20 lbs make that big of a difference on tongue weight.
grandmufti	posted 05-05-2002 10:19 AM ET (US) Just went out and reweighed my tongue on trailer.240 lbs tongue weight.Looks like the repowering to the 115 four stroke changed my pivot weight. How close to the 10 percent rule must my tongue weight be?I swayed just as much before the repower as I do now.Before repower I had 280 lbs on tongue.Should I bite the bullet and move the axle back on the frame?
jimh	posted 05-05-2002 10:30 AM ET (US) How many axles on the trailer? Single axle trailers seem more prone to sway.
Jerry Townsend	posted 05-05-2002 10:54 AM ET (US) Grandmufti - your tongue weight is in the ball park - 5 to 10 % on a single axle trailer and 5% on a multi-axle trailer. But going to around 10% doesn't hurt a thing and can help the trailer dynamics. Decreasing the air pressure can help - as it will give you a little more 'gripping' of the road - but don't go to 20 pounds - perhaps in the 30 to 35 pound range. There will not be more friction per se which is dependent on the weight and the coefficient of friction between the rubber and the pavement/concrete. Also have someone follow you on the road and see if the trailer is tracking straight. An axle that is not square with the trailer will cause the trailer to 'crab' behind the tow vehicle. ------ Jerry/Idaho
jimp	posted 05-05-2002 12:19 PM ET (US) grandmufti - Just have to say it, don't mean to be insulting. I assume you're driving straight without swerving from side to side in your lane. And that when semi rigs pass you, you are not unconsciously turning away and then back. Same with lane changes, that you make them smoothly. A wind gust could cause you to over correct. When I trailered my Montauk cross country in 1989, I was hit with severe cross winds in North Dakota, my top speed dropped to 48 mph in order to keep the trailer behind me. I had been able to do the speed limit up until that point (55-65). Also, maybe when you check your rearview mirrors, you're turning slightly in that direction. JimP
simonmeridew	posted 05-05-2002 06:16 PM ET (US) You might try putting something with a little weight in in in front of the console, like a full cooler etc. On the other hand, make sure you don't have something heavy in the stern that would try to counterbalence the tongue weight. Also, you don't have one of those trailers with a tilt pin mechanism do you? They always have some "slop" in them which can translate into side to side sway. Are the spring shackles tight on the axles? and the receiver mechanism on the rear of the truck nice and tight? Just a couple of things to think about. simonmeridew
grandmufti	posted 05-05-2002 10:58 PM ET (US) I moved my axle back 4.5 inches this afternoon and brought the tongue weight up to 310 lbs.The trailer is a single axle shorlander. I have had the sway get so bad that I almost lose control of the Van.The only way it goes away is to slow down fast.I will try towing with the 10% tongue weight and see how it handles.Only time will tell as the conditions need to be right to get it to sway.I don't relly want to induce it by jerking the steering wheel.Will keep you posted.Thanks for the advice.
triblet	posted 05-05-2002 11:34 PM ET (US) I have a single axle Shorland'r, a bit smaller (Montauk, about 2000 pounds). My tongue weight is around 100 pounds. No sway unless I do something abrubt. Have you checked the wheel bearings?
sklein	posted 05-06-2002 08:34 PM ET (US) Buy a pickup with Quadrasteer (Four wheel steering). It's now available on the GMC Sierra and Chevy Silverado. It does great things for towing, especially reducing trailer sway at high speeds. http://www.delphi.com/automotive/handling/steering/quadrasteer/ Check out the section on trailering. Steve
simonmeridew	posted 05-06-2002 10:00 PM ET (US) I've been thinking about this thread for a day now. I have towed everything from a 300 lb woodsplitter, a 12 foot aluminum boat, to my Montauk 5000+ miles, a 5500 lb GVW including trailer SeaCraft 2000 miles, utility trailers with 3500 lb of gravel, utility trailer with 1000 board feet of green lumber with serious negative tongue weight issues, 6000 lb excavators on a tandem flatbed, all with either a Tundra or formerly a Bronco. By the way I'm not recommending the excavator stunt, or the negative tongue weight, it was only by "personal necessity". I'm sure that many on this forum have ten times the towing experience that I have. Without trying to put words in anyone else's mouth, i.e.: my own opinion only: If you have a trailer that sways or in any other way is unstable, or you even think might be unstable, there is something seriously wrong with the setup and you are only asking for a situation which you are not in control of your vehicle and could lead to at the least undergarment soiling and perhaps loss of vehicle or boat or life. Go to a truck scale or gravel scale and take your time to get an accurate weight of all components, including tongue and axle weight. It sounds like you are on the right track with shifting the axle. But maybe your van is not quite the best towing vehicle, due to suseptability(sp??) to crosswinds and light rear end itself. What about vehicle GVW specs? Should you really be putting your boat on a single axle, or would a tandem be better? If the trailer is set up right you keep having to keep looking in the rear view mirror to see if the trailer is still back there, you can't even feel it. Just my opinion simonmeridew
grandmufti	posted 05-06-2002 10:51 PM ET (US) The new truck is out of the question as I tow with an all wheel drive 2000 Astro van with factory trailering package.Besides the van doesn't sway the trailer does.The van is rated to tow 5800lbs. I agree that a tandem axle trailer would be better for towing all the way around.But I have used this trailer for 13 years and am quite attached to it.Most of my tows are under 10 miles on city streets but the occassional 75 mile trip to the islands at highway speed are a little scary at times. I am a patient man and will work this thru one step at a time.My first step was to add tongue weight which needs to be tested.But I like the suggestion to get the whole outfit weighed so I will know for sure what weight I am dealing with.If it does not rain I will do it tomorrow.If after getting the tongue weight to 10% I still sway I will seek professional help on this forum. Remember I have short arms and deep pockets so if I can fix it for free or almost free I won't have to see if I can reach the bottom of my pockets.
triblet	posted 05-06-2002 11:12 PM ET (US) Quadrasteer, huh. Reminds me of my high school buddy Gary Stiles. He was into the old turtle SAABs, (three cylinders, two-stroke, pre-mix) and had several in his back yard. One day he cut the steering out of one and welded it into the back of another. He rigged up a shovel handle between the seats for a tiller for the rear wheels. He could drive down the road crabbed about 45 degrees to the line of travel, and parallel park it instantly in the tiniest of spots. I think he single-handedly increased attendance at AA meetings about 25%. ;-) Chuck
grandmufti	posted 05-07-2002 11:38 AM ET (US) Things I have learned today!My boat and trailer weigh 3800lbs not the 2800-3000 I had estimated by adding up the components.My tongue weight is 300 lbs not what my bathroom scale said. This means I must add back the leaf I removed from the springs to soften the ride 5 years ago when I replaced them.I think I will be Ok with the 300 lbs on the tongue as the test ride on the freeway went pretty well.I induced a good sway at 65 mph by jerking the steering wheel and the boat straightened itself after about 4 or 5 sways.Before I added more tongue weight the sway would have kept getting worse until I hit the brakes and slowed down. All these years I sat smug thinking I had the 10% tongue weight on my rig.I never knew I was towing that much weight.If you take anything from this post GET YOUR RIG WEIGHED you carry more junk than you realize.Never assume anything. The man at the building supply yard did not charge me for the weigh when I explained what i was trying to accomplish.Looks like I may have fixed it for free and will not have to try and get my short arms into my deep pockets.
JimU	posted 05-07-2002 12:03 PM ET (US) you might want to take your trailer to a trailer specialist and have alignment, springs, Hangers and hanger bolts checked for wear and loosness. JIM
grandmufti	posted 05-07-2002 12:20 PM ET (US) I am the trailer specialist.Eveything is tight and aligned.Although I will probably replace the springs this summer for preventive maintenance.I had a set break on another boat and have been running scared ever since.They do wear out and develope stress cracks over time.
grandmufti	posted 05-07-2002 12:24 PM ET (US) No offense to you Jim but I have found if you want something done right you have to do it yourself.Too many neer do wells out there.
jimh	posted 05-07-2002 03:27 PM ET (US) Would temporarily adding some weight to the tongue (so as to increase the tongue weight) be a valid test of how the trailer would behave if the boat were move forward (which would increase the tongue weight)?
whalerron	posted 05-08-2002 12:27 AM ET (US) I stumbled across this tonight. This is a very harsh example of the results of fishtailing... http://www.boatus.com/Seaworthy/13.htm
Dr T	posted 05-09-2002 09:44 AM ET (US) JimH, I believe so, expecially if placed on the tongue behind the winch and under the bow. tds
Jerry Townsend	posted 05-09-2002 11:18 AM ET (US) Jimh - That would give a valid test. Now, strictly speaking - the dynamics of a trailer is dependent on the location of the C/G of the load. As such, the test C/G should be close to the C/G should the boat be moved on the trailer - however, a small weight close to the hitch will have more effect on the hitch load and will not displace the C/G of the resultant trailer load all that much. Therefore - in my mind, your suggestion is good. ---- Jerry/Idaho