My NorthernLite porpoised when on concrete highways. I played with tire pressure, moving the camper COG,etc with no luck. This year I decided it was time for new shocks. Went with KYB monomax. No more porpoising and greater stability on corners. Concerning your overloads, I think your Timbrens may be preventing them from contacting. I don't have airbags or overloads so I can't say how they work, but my Timbrens get the job done.
"04" CHEV 2500HD DURAMAX DIESEL REG CAB SRW
2010 NORTHERN-LITE 10-2 SPECIAL EDITION
15 YR OLD BORDER COLLIE (LADY)(no longer with us 6/23/11)
You can't do much about concrete highways... There are a couple of stretches of new concrete highway around here that are so bad that it doesn't seem to matter much. Load, wheelbase, speed... NONE of it matters. You're going for a bucking-bronco ride.
I've been down it with my regular cab dually empty, and with a load... Same.
I've been down it with my shortbed extended cab 1/2 ton... Same.
My uncle drove an empty 10-wheeler down the same stretch... He said he thought he was going to shake apart.
2002 Chevy 3500 DRW 8.1L/Allison
2000 Palomino B1500
...and the reason why I need a DRW to haul a Palomino:
2004 United 7x14 tandem axle enclosed toy trailer
2011 PJ 8x20 7-ton deckover equipment trailer
X 10 on airbags being over inflated etc etc. Air bags give a very soft and bouncy ride after all they are just a set of balloons back there, squeeze a balloon and see what it does...
If you are bouncing something is overcoming the intended shock action. I would look at a set of Stable loads and insure you are getting early (as in static) engagement with your overload springs.
I would also INSPECT your shocks for oil leaks to insure your bushing are not wallowed out. Do you run your shocks on '9' when loaded???? Are you SURE you have them set on a high setting and NOT on 1 or 2. I have had clients that wanted a refund on the Rancho 9000's I installed because their Jeep bounced so bad they could barely drive it...checking in every single case they had turned the setting knob in the wrong direction...
Don
17 Oaks Ranch, Texas
US Army (RET)
'11 F350 4x4, CC, LWB, DRW, Lariat
AF 1150, solar, satellite
Vietnam Combat Veteran
On a concrete highway, you are bouncing because the distance between your axles, combined with the distance between expansion joints, combined (usually) with your speed sets up a harmonic that no suspension system can compensate for.
mkirsch wrote: On a concrete highway, you are bouncing because the distance between your axles, combined with the distance between expansion joints, combined (usually) with your speed sets up a harmonic that no suspension system can compensate for.
That could be true, but speed is a part of the equation and not independent of it. I can pass in and out of harmonics based upon speed at which I travel, shocks and other factors.
Is the harmonics appearing on any concrete at any speed or is there a certain speed or zone they appear...
Survey,
We have about the same size T and same size C.
I've used Lance camper struts for 10 years, and I do like them. I get no porpoising at all. They tend to 'tighten up' the whole rig, dampening the porpoise. I notice a moderate difference when they're not on.
However, I don't think they actually make $400 worth of difference. At $400, I'd pass.
What you want are:
Tork Lift Stable Loads
An extra secondary spring in addition to the factory one. (sometimes called overloads. An overload spring is actually that big flat one on the bottom of the pack)
Mine was a composite of a Camper Special thick secondary and a pair of thinner 1-ton secondaries each style with about a 1200 lb. rate.
and longer U-bolts and a longer centering bolt.
H.D. shocks on all 4 corners, rr ones on the stiffest setting, front ones with no adjustment.
I like Rancho's and KYB's and have had good luck with both. The KYB's tend to get stiffer as they get hotter, as in rough road conditions, with no median position, since they are gas charged and always pushing up, which i think is a plus, over all.
With this set up I've been able to carry 5000 lbs. in the bed with no issues.
The only downside for me is the empty ride. Does riding a brick come to mind?
Also, how flexible is your TC height increaser? I hope not flexible at all.
The only other thing is how thick is your camper pad? Thin rubber ones are the best as they have little deflection or recoil.
Just my opinion (after using them) but I don't like the issues you get with air bags. Lots of recoil here. And they have a very narrow range (of air pressure) that they will do any good. Same with coil springs. Big old dumb leaf springs are still the best for ride control and carrying heavy loads.
regards, as always, jefe
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Some have reported with the Happijac tiedowns the rear bumper on some trucks flexes too much . I believe they sell an additional bumper brace to correct this . Just a thought .
Don't play with tire pressure. Inflate to the recommended rating. For example: I have 10 ply E-rated tires that indicate 80 psi on the sidewall. The dealer that I bought the tires from recommended 80 psi when loaded, and without the camper, he recommended I run 42 psi pressure. After 4 years with those tires, they still perform well and have never had a problem...Interstate highway speeds and gnarley mountain roads. I have air bags that I use to level the rig front-to-back, "Stable Loads" to facilitate engaging the overload springs, Lance struts to help dampen the camper overhead of the truck cab. Now, regarding "porpoising", and assuming that the base/pad/mat that the TC sits on is not spongy, allowing the TC to spring front-to-back, side-to-side, My most impressive addition to the ride was the addition of KYB MonoMax shocks that have done what they were designed to do and dampen any of that stuff, including those aweful concrete highway engineering mistakes. When I encounter those, it's up-and-down, once or twice, then smooths out.
As you can see from my sig, I carry a pretty heavy camper on a 150/1500 series PU, and after 4-5 years of my kind of camping (Rocky Mountains), I'm pretty satisfied.
Cap'n Bob
1996 Chevy K1500 4X4 Short Box, 5.7L Vortec, E rated tires, Lance Model 820 with Cabover Struts, Firestone Ride-Rite Air Bags, KYB MonoMax Shocks, Torklift Stable Loads, Happijac Truck Camper Tiedowns and Turnbuckles, Honda Eu2000i Inverter/Generator.
sorry to get back after so long, thanks everyone for the tips. As soon as I can spend a little money I'll be looking to use a couple of these suggestions. I sure appreciate it.
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