Morning.I have a 2015 Chevy 3500 HD short bed, Crew with the duramax. It's setup with RS9000's in the rear (set at 9) and stable loads. Front shocks are Bilstein 5100. I have a Hellwig stabilizer in the rear. Truck is stock otherwise. No airbags. I have a fairly heavy camper and took this setup out over the weekend for my first road trip. Everything went very well and I am generally pleased with the way it handles. However - I notice that I get an annoying fast bounce (I think from the rear). It's not a porpoise. It's more of a chucking. It happens a couple times per second it seems, when I am rolling over small bumps at highway speeds or over 40mph. It's not constant, and any larger bumps or dips are handled fine. It's more of an annoyance than a drivability issue.I am thinking it's because my auxiliary springs are so pre-loaded with the stable loads. They are almost flat, but they aren't so flat that they touch the lower springs. i have maybe and inch and a half left. The truck sits nice and level though.Would anyone have a suggestion to calm the sharp bounce and improve the ride?I was thinking my options might be:Add air bags.Change the Bilsteins in the front for RS9000.Install stiffer rear aux springs (SuperSprings).Any insight would be appreciated.

Try adjusting the rear shocks first.

I am sure it is road surface induced. It only lasts a second or two and it doesn't happen all the time. The strange thing is that I don't FEEL any bumps in the road when it happens, and it recovers quickly. The larger dips and bumps are handled fine. I was going to try to lighten up on the RS9000's which are set at 9, but I thought that might be worse. I'll move them down a notch and see what happens.I don't know the rear axle weight yet, but I am sure I am at or slightly over the limit of 7050. I plan to weigh it Columbus Day weekend at a CAT scale. The camper is an Arctic Fox 811S. Center of gravity is over the rear wheels. Yes, I know it's a 4300 pound camper loaded. I'm very happy with how the truck handled except for the annoying choppy bounce every now and then. It didn't seem to matter whether I had a full 51 gallons of water or not - I tried full/empty and not any significant difference. I am really thinking it's induced by the helper springs being loaded like they are.OR, it could be the way the camper sits in the bed. This truck has a large lip at the forward end of the box, on the top of the bed. The rubber bumpers on the camper barely touch the front of the bed, and the exterior wall of the camper hits the lip. Bad enough that it squeaks and on this trip I had to grease it or I would have gone crazy. I am going to have to modify these rubber stops on the camper to get them out another inch or so to keep the camper off the bed rail.Finally, I have a rubber truck mat in the bed - maybe there is some give to that? What about adding Cabover struts? I have heard pros and cons, but generally people say they help.

The fact that you get the problem at higher frequency bumps rather than lower frequency bumps makes it sound like you have hit some sort of resonant frequency that your dampers aren't handling. Maybe try to find a piece of local road that induces it, then try different adjustments on the dampers either way to see if one of them improves it. I.e. don't just try making the dampers firmer, try making them softer too.It could be that the resonant frequency of bounce of the tyres (which probably relates to their pressures) may be hitting a frequency the dampers are failing to damp.Steve.

Wrong Bilstein shocks in front. 5100's are Bilstein's off road shock. You want the payload shocks #4600.

Sharp Bouncing | Good Sam Community

jeffreyduncan
Explorer
Jan 07, 2016
It definitely won't be. I'm probably slightly over. They are at 80 in the rear and I can't lower it. I could in the front. I'm convinced it's the Stable loads. Without them it rides like it should. They cause too much preload with my heavy camper.
Ski_Pro_3
Explorer
Jan 07, 2016
I don't see any mention of the tires you are using. Especially the air pressure. You might want to try lowering the air pressure 5 psi at a time, starting with the front tires first.

If you discover the ride improves, the next step is to confirm your tire load capacity is still within limits with the reduced air in the tires.
jeffreyduncan
Explorer
Jan 06, 2016
I wanted to update this thread with some information. I had the dealer fixing my slide out motor (replaced) and while he had it, I took the stable-loads off the truck because I was pretty much done for the season, and they give a harsh ride on the miles of dirt roads I drive. So the story is that I picked up the camper WITHOUT them installed, and the ride was amazing. No bounce whatsoever. So I am convinced that these stable-loads are root of the issue causing the bounce. As stated, they nearly flatten the helpers to near horizontal.

So my next move is to cut them down a couple inches, to retain some of the value they may provide in roll.

That's all.

Jeff
jimh406
Explorer III
Oct 14, 2015
trail-explorer wrote:
Skip the airbags, they will unload the suspension and make the ride even more harsh.

Obviously, this isn't always true. You do have to understand how they work though and use air bags to complement your suspension. Many of us are doing this using tried and true methods.
trail-explorer
Explorer
Oct 14, 2015
Sounds road surface induced.

Skip the airbags, they will unload the suspension and make the ride even more harsh.
Bedlam
Moderator
Oct 13, 2015
Although I ran Rancho 9000 series, I did look in to the Blistein's when I was shopping. The 5100's are dampened softer for off-road use where the 4600's are valved differently for heavy service use.
jeffreyduncan
Explorer
Oct 13, 2015
Definitely not in my experience! Even without the camper on the back, and before I adjusted the rears, I noticed a considerable difference in the stiffness up front with the 4600's compared to the 5100.
Garyl53
Explorer
Oct 13, 2015
I was told the 4600 and the 5100 (0-2" version) were identical other than the finish. Is this accurate or not?
jeffreyduncan
Explorer
Oct 13, 2015
I wanted to report back after my trip with the new HD shocks up front. HUGE difference. I also backed the Ranchos down to 7 and had a full water tank. Tank was less than half on the ride home and as another poster said - not much difference. I think the main difference was the 4600's up front. I would say they cured the chucking by 98%. Thanks to those who pointed out I had the wrong Bilsteins up front!
ab257
Explorer
Oct 08, 2015
Wonder if water sloshing in your tanks contribute to the weird bounce.