What is the minimum clearance I need between the truck cab and camper overhang?

[Sterling1]

I'm getting a 2024 Ram 3500 DRW long bed crew cab truck for my 2000 Bigfoot 10.6 truck camper.  My measurements show I'll have about 1.5" clearance between the truck cab and camper overhang at about the center of the cab.  I'll have about 1/2" at the shark fin antenna but I plan on relocating that.  I'll have a better idea of the clearances when I get the truck.  

What is the minimum clearance I'd need at the center of the cab and at the very front of the cab to accommodate frame flexing?  

Thanks for any input

[Camper_Jeff___K]

I built a 1" insulated lift for my TC thatworked fine for several years but it only provided 1/4" cab clearance. I recently built a 1-1/2" insulated lift which gives 3/4" lift. It has never caused an issue. I may have posted a spammy video here about it last year. The new lift also helps center and keep straight in the bed, how the TC sits.

[Grit_dog]

I’d say not may have the “exact answer”. 
1.5” seems a bit light, but may work. Probably fine under normal conditions but hitting a big dip or frost heave at highway speeds might test that theory. I’d shoot for a bit more. Nothing a sheet of plywood or 1” foam under the bed mat won’t cure. 

congrats on the new rig!

[Sterling1]

It seems like if it did slightly contact at the center of the cab roof that it wouldn't cause any permanent damage but would give me a warning that I need to do something about it.  It also depends on how the cab and camper move in relation to each other.  I.e., if it was a straight pivot at the cab to bed interface then 1 1/2" at the center of the cab would equate to about 3" required at the windshield.  I need to figure out if I can modify the shark fin antenna but keep it on the cab roof or completely move it somewhere else.  

[stevenal]

Also check the distance above the rails. My 'foot dealer had to run and get a foam sheet to get me home when it appeared the camper would hit the rails. I now have a 2X6 built platform that keeps my camper centered also.

[Sterling1]

My camper is 21" from the bottom to the part that overhangs the bed rails.  The Ram 3500 bed rail height is about 20.2"  

[MORSNOW]

There is a lot more movement up there than many realize with truck frame flex and cab over bounce.  I'd want at least 3" clearance, which would be easy for you to do with a flat frame built with 2x4 or 2x6 lumber or a sheet of pink/blue insulation board for support

[Sterling1]

I've sen 3" mentioned before.  I've also seen some comments that some Fords had more frame flex than other trucks.  My current truck (2000 K3500 crew cab long bed) has 2 1/8" between the center of the cab and the bottom of the camper overhang and hasn't hit in 20 years.  But I only use a 1/4" thick rubber mat in the bed which minimizes the amount of camper bounce.  

Truck manufacturers brag about how strong their frames are on new trucks, I just wonder if that translates into less flex between the bed and cab.  I'd prefer to keep my center of gravity as low as possible and minimize the amount I have to raise the camper.  

[StirCrazy]

I have about 4, i could get away with and feel comfterable with 3. 

frame flex doesn't mean it is weak, a fram that will flex in most cases will usaly be stronger to a point as it is able to adsorbe slight movment where as a ridgid fram can't and will be work stressed and eventual fail.  now we will probably never see thins in our picks ups but just wanted to put that out there. 

the major issue you are going to see is if the brand crowns the bed for weight handling, this will let the camper rock back and forth more which lets the cabover get closer and farther away from the cab roof when hitting bumps and even accelerating and braking.  some people have made up for this by shimming a bed suport up to make a flat surface for the camper to sit on but then your defeating the purpose of the crown, so I am not sure what the answer is in this case, maybe some one with a crowned truck can chime in on this one, but it is a good idea to get a knowen strait edge the length of you bod and see if the bed is crowned or not then you know.  

[Sterling1]

As far as I know the crowned bed is limited to GM trucks but I'll verify the Ram bed isn't crowned with a straight edge.  

[MORSNOW]

GM pickups have much less flex than a Ford, you can search frame flex videos and see the drastic difference.  A standard rubber bed mat will also provide cushioning while helping hold the camper firm, the problem lies in many go cheap and heavy by using horse stall mats that are three times thicker and offer plenty of rocking potential.  My setup is a standard rubber bed mat and an aluminum superstructure camper with minimal movement up top, but it still does move some.  

[Grit_dog]

Fords were flexy until the 2017 Super Duty chassis. Before that they still had a c channel frame where Dodge and GM went fully boxed in the early 2000s new models. 

[Sterling1]

I really wanted to make a GM truck work since they will let you get a gas engine in any trim line.  The problem I ran into was the 2024 Truck-Camper Loading guide was completely wrong for the cab height.  It showed the cab height as 40.8" but I just happened to measure the cab height when I was taking some other measurements and it turned out to be 44" and that didn't include the shark fin antenna.  I'm glad I found out before it was sitting in my driveway although I could have dealt with it.  The ram is 42.5" which was enough to sway me that direction (among some other things).  Ford was higher than I even wanted to consider.  

I'm hoping to be able to trim my current K3500 bed mat to fit the Ram.  I'm also hoping that the Ram frame flex is low enough to let me get away without building a platform.