The "Spread" of Ignorance

I agree with most of what has been said so far, that dump valves are good to have in tight spots. Ten feet of wheelbase less at the flip of a switch is a good thing running NYC and the Northeast every week.

But as for extending tire life by using a dump valve, has the opposite effect in most situations. A trailer that was designed to have spread axles but won't stand a u-turn without a dump valve is a POS anyway. These hands that feel the need to flip their dump valve on every time they turn the steering wheel, running through truckstops and every intersection spewing off air, their equipment would be alot better off having no dump valve.

While making a turn, closed tandems as well, one axle is fighting the other in a twist. Unless you can raise an axles tires completely off the ground this wear is unavoidable. To just dump the air off an axle under a load, most trailers will still have considerable ground pressure, thus causing the tires to side slide while rolling straight, having a cheesegrating effect unless turning on slick finished concrete or some other smooth surface. Most intersections are not what I'd call smooth, and definately not truck stop parking lots. Most are rutted out and have potholes which cause the dumped axle to skip, hop and bounce across unevenly chewing and beating your tires up way worse than the normal twisting while under pressure.

About whether the front or back should be lift axles, I'm sure it depends on the rigging and what it's doing. Tire size, ground clearance, and whether platform, dump, or hopper bed would decide. Looks way more kool to raise the front one though, leave the back end down on any trailer.
I got a Fontaine flatspread with hendrickson suspension. The front axle is the obvious easy one to lift on it just for the extra clearance created by the trailer arch and a high fifthwheel.

 

359kool, I have to disagree with you here...I have run spread axles for the better part of three decades and even had a Spring ride spread axle in the 70's.
I have seen aluminum spreads break just ahead of the front axle because some fool attempted a U-turn with a heavy load.

I couldnt keep tires on that old spring ride spread and the first air ride spread that I had was hard on tires as well (Didn't have a dump valve) Ever since then I have run a dump valve on the rear axle on every trailer I've owned for two reasons...

1. It reduces tire wear in tight turning situations (Not completely but quite a bit)

2. It reduces sideways stress on the frame of the trailer in tight turning (loaded) situations by a lot! ( This is very important if you run an all aluminum trailer)

I don't use the thing at intersections because that's not really a tight turning situation but I have found over the years that it has greatly reduced the wear and tear on my trailers and on my tires.

 

I said lifting the axle not dumping it
they used to, I havn't run a spread I could lift an axle on in probably 13 years though. I think I'd be beyotchin up a storm if I had four axles on the ground and they charged me for five

 

No it's cheaper, last time I pulled a 2 axle trailer with a front lift on the ohio turnpike it only said "4 axles" on the ticket. The savings is trivial but it did only charge for 4 axles.

While the tires are sliding sideways there is no weight on them so you don't get the "cheesegrating" you talk about. The only 2 flats I have without dump valves have 4 axles. And the only reason I don't have one on them is because their not needed. I can force the 3rd axle down which will pick the back 2 axles off the ground (empty). BUT with 19' of "tail whip" you've gotta watch out where you do it. (however you can make a U turn in the middle of a 2 lane highway if you want, it turns amazingly sharp)

Finally someone else that get's it.

 

Um........Good luck. If you do actually pull a U turn with a big load please have a video camera running. I've seen some have the rim hit the pavement when the tire rolls over but never seen one lose an axle while I was watching.

 

I was following a piggy back truck delivery driver one day years ago we were coming up to the GW bridge NB on I-95.He had four bobtails total with most of the axels off the ground.He might have been blowing smoke up a much younger driver's tailpipe but he told me he had to pay toll on all the axels.

 

The biggest idiot I ever drove a truck for in was in Tulsa,OK.the company was Kreative Trucking.The owner shared your opinion and wanted to run caps to boot.I saw more caps blowout and trailers break apart in the year I was there then before are since.

No dump valves and heavy loads are a bad combo.I was jacknife backing into a steel warehouse one day and had my front axel brake out from under the trailer Without a rear dump valve that front axel is torqued ever turn you make.

At Colt Truckline the year before same loads same equipment aluminum spreadaxel flats with rear axel dump valves no problems at all.Thats all the proof I need to think what I do on the subject.

 

All I meant was dumping the bags ain't necessarily better for the tires every time just because you're turning.
If you've been behind one before turning where its rough as hell and hear PSSSSSSHHHHHTTTT, you can see how smooth the assend of his wagon is while it's just "gliding over" the ruts.

You're probably the onlybody here needin to see u-turn videos to be convinced. Alot of trailer manufacturers don't install, recommend, or warranty after using a dump valve. Why? Because of the idiots afraid of axles and tires ripping out and frames breaking that dump 40,000 lb of load on a 20,000 lb rated single axle every time they turn thinking they reduce the stress on that axle..

Heres the way you can prove that dumped axles carry "no weight", and the tires don't ever leave black marks or wear from sidescooting and rolling.
Crawl in a rut or pothole so you are surface level at a TA entrance. Then have somebody else video and instruct drivers with various different loaded spreadaxles to dump their airbags before they turn in and run you over.

 

If most of the weight winds up on one axle...That means it's being taken off of the rear axle that's been dumped. There is still a little weight on the dumped axle but not much and that's the point of dumping...To take the stress off of tires and trailer frame rails.

 

The warranty comes into play because drivers get busy don't pay enough attention and forget to turn the dump valve off and they going down the road with one axle with all the load.
A lot of drivers hook up a light that's on when the dump is on that is highly recommended by me.
No more comments on this by me.I don't try to convert anyone on anything anymore.