do weight distributing bars weaken with age?

Timeking wrote:
I have been towing a 24ft 5500 lb TT with my 5.3L V8 Trailblazer for over 40,000 miles. Back when I first got the hitch, the trailer and the trailblazer sat level. Now I notice that the rear sags enough to notice, and it would seem that those bars being springs might have lost some of their original tension. Does this happen?

PS: I think I read all the posts on WD hitches here.

A few questions:

What year Trailblazer?

What is the size of your WD bars? (The weight rating)

Do you know your loaded tongue weight?

When did you notice the sag? How many miles ago? The setup is 40,000 miles, so trying to back into how many miles were OK and now not OK.

Is this a square bar hitch? (trunion bar)
Is this a round bar hitch? WD bars are round.

What brand hitch is it?

Any chance of pics of the hitch hooked up to the truck and camper?

Sorry for the so many questions, need more info to help give a better answer to tell you were to go looking. Bending a WD bar is not impossible but in most cases not likely which means the cause is somewhere else. 40,000 miles on a hitch is not a lot if the hitch has been maintained and the loads are within the ratings and set up right. If the WD bar is bent, then odds are high it is still bent and once we know more about your hitch it can be spotted if it is bent.

Hope this helps

John

Well EVERYTHING weakens with age. Especially things subjected to "duty cycles".

However your steel parts should take many many many years, maybe hundreds to see any real effect in actual change to tensile strength.

So dont worry.

I agree its probably your suspension moving parts that are changing for the worse.

During our 8000 mile trip I had to go up to link #4 to keep the trailer and tow vehicle level. The head is definitely worn as I can jiggle the arms around quite a bit, and I don't remember being able to do that 6 years and 50,000 towing miles ago. So after the financial dust settles following this long trip I am going to order a new head.

I am also going to write Chevy a letter and tell them how amazed I am at the engineering that went into my 5.3L Vortec and transmission. I did my absolute best to destroy this vehicle between Florida and Glacier NP via Texas and Michigan's UP on the way back, and the thing only burned one quart of oil. Wow!!

I am also going to replace rear shocks and front struts, and have my wrench evaluate all the springs, the whole suspension and steering.

If you see noticeable wear on the hitch head or the ends of the bars that insert into the head, that will make a big difference. I replaced my bar ends once and it was the equivalent of about 1 link. I'm sure the hitch head was affecting it just as much with as worn as it looked. I acquired the hitch parts used from the owner of the trailer I bought at the time. I'm not sure he ever greased anything so there was a lot of wear. I've since replaced the hitch head but the they are of two different designs so I can't say how much impact the head wear had on things. The next most logical thing is that you bring along more now than you used to. Or it could be any of the other things people have mentioned. I think bar end and hitch head wear is the most likely however.

Spring steel is expensive, tough and made to flex for millions or more cycles
before they start to fatigue...

But...they can be over flexed to go beyond their designed range (plastic) and
into the range where they will NOT go 'back' (yield)

This is basic strength of materials science, or metallurgy classes

WD Bars are NOT static in usage, but are preset in a static condition

Meaning while they work...they have a range of flexing that the WD Hitch
System imparts on them. That includes the TV/TT setup plus the biggie: The
Road conditions & how fast

Those Whoop-d-doos will un-weight them (un-bend) and over-weight them
(bend them more)

The faster you go over those Whoop-d-doos...the higher the chances of over-bending
the WD bars (no matter round or trunnion). Not just a one time thing, but
over time (many cycles) will or might over bend them to fatigue them

Think of your coil spring or leaf spring suspension on your car/truck/SUV/etc
Same thing and they do have a cycle life span

I am pretty sure/certain that the holes that the spring arms go through have expanded in size through wear. I had to go up to link #4 to get decent leveling (and freedom from the wind in Montana blowing me all over the road). Made it home fine. Having towed this TT almost 50,000 miles, I'm having everything on the tow vehicle checked, and replacing worn parts in the hitch assembly. As far as greasing, these things don't keep the grease where the grease needs to be, and that is why the holes got enlarged.

How about bloat?

BarneyS wrote:
Another possibility is that the receiver on the truck is bending upward when the bars are tensioned. Maybe a weld broke or something cracked in the receiver or the mounting area on the truck.
Worth taking a look as it has happened in the past.
Barney

Agree, receiver flex happens

My original hitch head egged out where the springs bars attached. I was towing a heavy bumper pull toy hauler and got about eight years out of the head before I had to replace it. I am still using the same bars and have not measured a diameter difference compared to new ones. My old hitch head is now dedicated for towing dead tongue weight - I have it set up at a different height so I do not need mess with my WDH setup when I occasionally tow a lighter trailer.

Another possibility is that the receiver on the truck is bending upward when the bars are tensioned. Maybe a weld broke or something cracked in the receiver or the mounting area on the truck.
Worth taking a look as it has happened in the past.
Barney