Isuzu air ride ?

[shooter51]

Well, I finally got my Isuzu NPR, 14.5 K, 120 inch wheelbase, tow rig rolling. I haven't pulled my 26 foot 5'er yet but I have towed a couple of TAG  travel trailers and a few boats. Power and acceleration is not race ready (4 cyl turbo diesel) but merges easily (acceleration) stops well, and changes lanes with confidence.

I ain't gonna win any pulling contests, but overall, I'm happy with the all around performance. The fly in the ointment is the quality of the ride. Un loaded, (bobtail) at freeway speeds, the bounce, buck and shimmy is memorable, (short wheelbase and sitting right over the steer axel) on all but the smoothest of roads. I had to glue down a foot rest next to the go pedal, because the bounce under my throttle foot, going up thru the gears, quickly gets out of hand.

All of her bad habits are much more manageable with a load on. I use a WDH with my 32 foot, enclosed, dragster trailer, (all up loaded ~6800.lbs) It should be MUCH better with the 5er, 'cause I can shift the hitch pin as much as 14 inches forward of the axle centerline. (the 5er is rated at 8600 Lbs. GVW,1600 Lbs., pin weight. but I'll never likely have that much crap in it at one time.)

As harsh as the ride is, I've been looking for an air ride conversion. If it was a pickup, up to a Ford F-550, I could get a conversion off the shelf, but, because it's a straight truck, commercial and an import, none of the conversion outfits, I could find, want to play. I found several setups that would work, with very few modifications (like the Reyco-Granning model RD-11-KC and the RD-960-C. ) all refused to even discuss modifications. The R-G setup is a "Z" shaped, forward pivot bar (from the front spring hanger) that clamps to the axel and the air bag is behind the axel. panhard bar, shocks and factory sway bar retained.  Neat, clean and bullet proof, I think. (wouldn't be a big deal to replace the panhard  bar with a watts link)

Am I chasing a well found unicorn again ?

I had even considered pulling all the spring leaves, except the bottom one, and mounting a double convoluted bag on top of the axle. Leaving the top overload spring would not be a problem, the way the spring pac is arranged. Even this simple a setup would allow 10 inches, or so, of ride height adjustment, wouldn't that be cool? (I would have to change to longer stroke shock's, but Monro stocks them)

Let's bring the collective minds to bear. Am I crazy or just lost sight of the box?  (sometimes, I look for reality, in the rear view mirror)

 

Thanks, Paul

 

 

[NoDirectionHome]

Air springs are not a panacea.  The direction I'd go is to weigh the truck front and rear, then go find a GOOD spring shop to help you re-spring the the truck for the appropriate load you intend to use it for.  I'd also mention the idea of progressive or dual rate springs.

[shooter51]

I agree, air suspension is not always a fix all. In my situation, it might be adjustable enough for the various rig's I tow. I have 4 trailers I tow on a fairly regular basis, from 3500 lbs to 11,000 lbs, with a 4 bay, angle load, horse trailer that shows up occasionally. The 4 legged go go dancers don't seem to care for the ride and my sit bones don't either. I'm old, I want a smoother ride, just not sure how to get it.

 

Thanks, Paul

[noteven]

Shooter51 - take a look at the manual control valve used by Canadian Load Share on their kits. Consider one of those if you decide to add the air spring as you mentioned. Sizing air springs is a bit if a science as well.

 

Firestone Air Suspension design guide

 

[beyerjf]

Trying to get any suspension to react accordingly to a range going from no load to full load is the holy grail of engineering. I bobtail 20,000 miles a year in an Argosy cab over, the air suspension has little air in the bags and it is rough at times. Your little Izuzu might benefit from air ride suspension, and similar sized trucks are equipped with air. It is still going to be rough. No way around it. 

[shooter51]

I recently scored a steel flatbed ~600 Lbs. when I get the genset, compressor, tool/storage boxes and transfer tank bolted down and covered, most of the annoying bounce issues should be gone.  With the pin/gooseneck forward of the axel centerline, the trail weight should improve the tracking and chucking. I'll have to log some more miles to know for sure but, An air ride pin box or receiver would not be out of the question.

Adding 800 to 1000 or so Lbs. may improve the bobtail ride enough. Remember, this rig started life as a 157 in W/B box truck with a 8500 Lb. cargo capacity.

Thanks, Paul