is there a crown in the 8 ft box on 16 gmc

[diver57]

Hi thought I read somewhere that there is a crown in an 8 ft box on the new chev;s and Gmc
Reason I am asking is because my new northern-lite seems to really bob up and down
when driving.
Anyone help me with this, whats the solution.
Thanks

[AnEv942]

Wonder if poly foam insualtion board might help- crush to conform?

I havent used but others have, mostly for raising camper, so maybe they might chime in on other aspects of using the board.

[Jim_Carolyn]

I've been over this issue of the crowned bed and the porpoising effect and fighting it for the past year.

I've got all that stuff on my truck, air bags, stableloads, new bilstein shocks, front timbrens, rubber pad, and pads to level the bed.

Maybe it's better, but I still have problems on rough roads - especially concrete. I've decided that the camper is just too heavy for the truck - and it's a 1 ton truck.

[CAJW]

jimh425 wrote:
Older threads suggest that the crown exists, but I think a horse stall matt from Tractor Supply or similar should take care of it.

Maybe for some, but in my case no. I've had Tractor Supply horse mats from day one, but had some slight rocking/ porposing on certain sections of road. I had to add rubber strips 3/16" thick, 12" x 48" front and rear to help compensate for the crowned area. Rides possibly a tad bit better (less porposing) , but sometimes wishful thinking influences percieved results. At the very least, it sits level.

[GeoBoy]

I have a bed mat in my truck bed and then I added a 12" deep X the width of the bed 1/2" thick rubber piece in the back of the truck bed to help compensate for the crown.

[jimh406]

Older threads suggest that the crown exists, but I think a horse stall matt from Tractor Supply or similar should take care of it.

[MORSNOW]

I checked my 2012 6-1/2' box with a long level this spring, there is definitely a crown in the middle of the box, so I'd say all 2011 and newer GM's have this crown in them. I could not see the crown, but the level does not lie. I put two semi truck mudflaps under the back half of my rubber bed mat and my camper now stays level. I noticed looking at photos from past years and I can see that at times my camper looked tilted to the rear, other times level, so I raised the rear bed mat to stay level.

Heck you can see it in the picture in my signature block. Here is a larger copy of the same picture (sorry it wasn't straight on from the side). Look at the camper line and the truck box and see the taper to the rear. The cabover looks leaned back also, but the truck roof slope may make it look worse than it is.