Equilizer issues?

[ToddP]

I bought a home built tandem 16' flat bed trailer for tractor hauling. Problem is that if I haul it empty there is significant bounce at certain speeds. As I recall from last year about 35-45mph. I best describe it as bouncing in your seat with a shake and vibration. I am suspecting the springs and equalizers not quite right. I have tried varying tire pressures with no luck. Attached are some pictures. The equalizers are 7 3/4" x 2 11/16". I am thinking I should try 5 3/4" as the easy fix, before shorter springs. The 5 3/4" I have seen are 4" high. Not sure if that extra inch and 5/16 of height is an issue or not. Any thoughts would be appreciated.

 

[Diamondpilot]

I would have your tires spun balanced first. I bet you will find a tire with a broken belt or a bent rim. I see it all the time in the trailer business I run on the side.

Its also the nature of the beast with them MH axles and bias tires. I can never get the wheel centered and the bias tires flat spot. For that reason I have refused to tow or work on them for the past 10 years or so.

Good luck.

Chris

 

[pjbci]

I would have your tires spun balanced first. I bet you will find a tire with a broken belt or a bent rim. I see it all the time in the trailer business I run on the side.

Its also the nature of the beast with them MH axles and bias tires. I can never get the wheel centered and the bias tires flat spot. For that reason I have refused to tow or work on them for the past 10 years or so.

Good luck.

Chris

I agree completely.

 

[Case485Guy]

I am betting tires also

 

[Stimw]

It looks like the geometry is off on the shackles, the spring ends are too close to the center mount.
Not sure about finding shorter length springs without a hassle, probably easier to re-mount the solid end hangers.
The suspension can't work properly the way it is.
I had the cords break on a tire on the interstate and I thought the trailer was going to come off the ground, it can really be a rough ride.

 

[ToddP]

Thanks for all the ideas. The tires are new last May and the problem did seem to start about then. I only pulled the trailer a few miles on the old mobile home tires when I purchased the trailer and did not notice any issues. The new tires are DOT approved, not M.H. tires so I am legal there. The place I bought them could not balance those type rims on his machine. I noticed that the new tires are 12 ply and the old were 8 ply making them likely a stiffer tire. Perhaps the equalizer arrangement not being 100% may not allow the suspension to act properly with the stiffer tire? Not sure, but will do some measuring for out of round when I get a minute and post results. Rims seem to be properly seated on the axle and tight. thanks

 

[Diamondpilot]

Thanks for all the ideas. The tires are new last May and the problem did seem to start about then. I only pulled the trailer a few miles on the old mobile home tires when I purchased the trailer and did not notice any issues. The new tires are DOT approved, not M.H. tires so I am legal there. The place I bought them could not balance those type rims on his machine. I noticed that the new tires are 12 ply and the old were 8 ply making them likely a stiffer tire. Perhaps the equalizer arrangement not being 100% may not allow the suspension to act properly with the stiffer tire? Not sure, but will do some measuring for out of round when I get a minute and post results. Rims seem to be properly seated on the axle and tight. thanks

New tires always need balanced. Look at a new car on the lot. Even with everything new they still need balanced.

That's your next step.

Chris

 

[Bird]

The tires definitely need to be balanced, as Diamondpilot said. But Stimw is also right "the geometry is off on the shackles". Look at the angle shown in the picture and compare it to the proper angles in the diagram in the middle of this page: Tandem-Axle Trailer Equalizer Kit for 1-3/4" Wide Double-Eye Springs - 5-5/8" Long Redline Trailer Suspension AP233

Way back on May 20, 1990, my brother bought new springs for his 35' fifth-wheel and we put them on in Ardmore, Oklahoma in preparation for a trip to Alaska. We thought those springs appeared to be a little too long, but we started out anyway on May 28. But the next day (May 29), we stopped in Grand Island, NE, and he bought another set of 4 springs of the proper length. Sure glad I had an electric impact wrench and a generator in my rig for us to change that whole set of springs in an hour and a half.

 

[6011Artist]

If you want to check for out of round, jack up the tire to be checked and spin it. You'll be able to see the high/low spots as they go 'round.

If checking to see if they are seated properly, while jacked up, place a bottle, block, anything beside tire and spin it. You can see if the distance between bottle/tire changes if it is pulled tighter on one side than the other. Again, you can see the wobble.

If tightening that type of wheel, snug all lugs and then tighten them equally by using the star pattern, tighten one, skip the next one until you've been all the way around. Pay attention to how much pressure you are applying trying to match with the last on each tightening, working your way around the 5 lugs several times until you feel they are locked down.

In my experiences, if a tandem axle trailer with equalizers is not pulled level, it will do the 'huckabuck' especially when empty. Get it on level ground and look or measure to see if it is level. If not, change your hitching height to level and I think you'll see a big difference. Pulling it with the front slightly lower will cause it to jump and snatch you as if you had no springs.

 

[Case485Guy]

Try these for balancing the tires if you cant find someone with a machine to do them. A couple of my friends(truckers) swear by these. I have nver tried them, so no first hand knowledge.
Tire Balancing Products