Trailer Has Loud and Excessive Vibrations Loaded or Not Loaded

Question:

I understand your comment about why people dont balance trailer tires because the weights may be bounced off when the trailer is empty. However, when Im cruising at freeway speed 70mph+/- my trailer starts to vibrate so excessively that it shakes the whole SUV and its fairly loud. The vibrations fluctuate in intensity from nothing to severe in a repeating cycle that takes a few seconds. I would describe the fluctuating vibration intensity like a tornado siren. Quiet to loud to quiet over a few seconds. This is really annoying, and Im sure its not good for the bearings either. The maximum intensity changes in correlation to the amount of load. The heavier the load the less vibration, but I rarely have it more than 1/2 loaded so the vibrations are bad. Ive tried a couple places to see if theyd balance them, but everyone turns me down. The trailer is a 54inch x 120inch single sled trailer. Its about ten years old. Im on my third set of tires and all 3 sets have done the same thing. Tires are 18.5 x 8.5-5. 5 hole. Ive also checked roundness of the tires. All sets have been out of round by about 3/16. I presume this would cause vibrations too. The last set of tires I pulled off had started to scallop on the inside 1/3. What would cause that? So, where can I purchase new tires or get the existing tires balanced to reduce/eliminate these vibrations? I used to own a small 4foot x 8foot folding trailer with smaller tires and never had a problem. Several potential problem areas here so any ideas you have would be very helpful. Thanks in advance for your input.

asked by: Gary

Helpful Expert Reply:

Trailer tires typically do not get balanced because manufacturers tend to match the heavy spot on the tire with the light spot on the wheel. It takes a special rig to balance trailer tires, equipment that not many tire shops have anymore.

The other issue is that the trailer tires we carry are rated for 65 miles per hour at most and a lot of other trailer tires are rated lower. I recommend checking the tire sidewalls to see if they have a speed rating. Staying under 70 miles per hour would be a good idea.

It might not be the tires at all. It could be the wheels. I would have a shop inspect the wheels to see if they are off. You will also want to make sure that your tires are inflated to the maximum psi as indicated on the tire. Trailer tires are made with a thicker sidewall. If under inflated the thicker sidewall will cause excessive heat and wear the tire out faster and/or cause it to fail.

The scalloping you see could be caused by scrubbing (dragging sideways) which happens on trailers with more than one axle when making tight enough turns.

Tire size 18.5x8.5 is an old tire size not used anymore. The modern size is 215/60-8, # AM1HP28. These are wide, short tires. The wider the tire the more of the road you are going to feel. As far as where to get them balanced it is going to be very difficult to find a place. You will need to call around and see if any shops have the special rig to balance trailer tires.

And as far as where to get tires, right here! I have linked our trailer tire FAQ article for you.

expert reply by: Michael H