Ideal Gap between truck roof and cab over camper overhang?

West Coast Mags

Currently mid way through my ultimate camper build. What I have so far is an old dodge truck that I swapped a utility bed on, but the utility bed rails are about 6" taller than a normal pick up bed. Ontop of the utility bed I have a 8.5' hardside truck camper. Due to the taller tool bed sides, I have a pretty big gap (about 18") between the roof of the truck and the bottom of the camper overhang. To fill in the space I plan to build a large storage compartment which will mount underneath the over cab portion of the camper. I would like to know from those with camper experience what they believe the ideal gap between the roof of the truck and bottom of the cab over portion of the camper would be. I really do not have a decent way to try to measure flex of the truck at this current stage of building, but in reality I do not see lots of extreme flexing from this vehicle on the menu at all, mainly graded dirt roads, deep snow. I would like to run as little gap as feasible in the name of reducing uplifting drag forces, (yes I know it will be like driving a wall) but I would like to reduce the effect as much as possible. Any input, or ballpark ideas what a good gap to shoot for is? I'm thinking about six inches, but really don't have any real world experience. Thanks in advance!
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Expedition Leader
I don't know if I can tell you what the ideal clearance is, but I run about 3-4" between my cab roof and the camper overhang. My usage for this rig sounds similar to yours. It's not a serious off road rig for us, but we do take it on dirt roads, mostly well maintained but occasionally not so well maintained. The camper does move relative to the cab, but I would guess that motion is limited to less than +/- one inch under all but the most extreme circumstances. We have never had camper/cab contact.

I do use frame mount tie downs, which I think anchor the camper more solidly to the truck compared to tie downs that are mounted to the truck bed. Obviously, there are springs in the tie down system, so that's where the allowance for motion comes from.

In case it matters, I have a Bigfoot C2500 10.6 that I carry on a '99 F350 supercab/longbed.


Ideal gap should equate to minimum gap. I would shoot for 1 and 1/2 inches minimum. If it ends up being one inch, then you are still good... maybe.

I have a Callen on an old Dodge. But it is bolt down "shell" type mount, not slide in. Camper manufacturers did not make different campers for each fullsized truck. They took the truck with the highest cab and put it as close as possible. My '93 Dodge fullsize longbed has a clearance of 1 inch or less, no joke. I think it is just under an inch eyeballing it, what I consider to be very close. I use my truck, loaded, twisted, etc, it does not hit. The Dodges for that year had a cab height an inch and a half taller than the Fords for that year. My Callen will fit the same year Ford like a glove as well... but with about a 2 and 1/2 inch gap over the cab.

One thing to consider it that the configuration and measurements will be different for old trucks... body parts settle, are adjusted, shimmed, things get tweaked. They aren't all the same even if they are the same model truck. So, it is not an exact sort of science. Shoot for your clearance and run with it.

I think I read somewhere on these forums that one manufacturer likes 3 inches of clearance.

West Coast Mags

Cool, 3-4 inches sounds lots better than the 6 inches I was thinking. The camper will pretty much need to be solid mounted to the bed, but the bed has a little allowance through the body mounts etc.
This is a pretty old thread, but here goes. I just mounted an Alu-Cab onto my '21 F150. It's mounted to a Yakima bed rack system. My first highway drive had intermittent air reverberations -- I could put my hand on the ceiling above the back seats and feel it. Felt like air was getting balled up or something.

I was at about 3" over the cab. Just raised it and will test tomorrow.

Any thoughts on perfect height for a hardshell RTT?


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