Tires: Rear End Sway Under Load, inflation pressure, rear tires

Question
QUESTION: Barry,

I have a Dodge Ram 5500 with a wrecker body.  The tires are Goodyear 225/70R19.5 with a load range F.  Front tires are "all position" (according to Dodge description)G647 RSS, and rear tires are "traction" G622 RSD.


Empty the vehicle drives just fine.  Towing a car I get rear end sway.  The body upfitter says that the tire tread is too aggressive and that is causing the problem.  Others have suggested that the load range could cause the problem but the tread will not.

Can my tires be the cause of the sway?  If so, can the inflation be adjusted to correct the problem?

ANSWER: Bob,

It is possible that the tire pressure is causing the problem.

So the first step in the process is to find the vehicle placard and see what it says.  This isn't a "Light Vehicle" as defined by NHTSA, but I'll bet the placard is in the same position as required by NHTSA - near the drivers door - meaning the door or doorpost.

The second step would be to compare the tire size and pressure to what you are running!

Check this out and let me know what you find and we'll discuss what to do next.

---------- FOLLOW-UP ----------

QUESTION: Barry,

Tires are correct size and inflation per the placard. This vehicle has under 1,000 miles and is equipped with tires by the factory.

Again, drives graet without a load.  Tow a car and we get rear end sway.

Answer
Bob,

I'm not sure if this is a duplicate post or not.  If it is, ignore it, please.

I will still like to know what the placard inflation pressure is.  I'm wondering if the tires are getting saturated - loaded such that they don't behave linearly any more.

So the pressure is needed if i'm going to pursue this line of thinking.