Over Cab Clearance

[camper rich]

I have built a storage box that will fasten to the underside of the overhang on my 2016 Grandby. It appears it will only have 1/4" to 3/8" clearance over the cab at its lowest spot. I have already added the 3/4" plywood in the bed to get that much clearance and I hate to add more if I don't have to.

Any ideas on if it is too close. The truck is a 2008 Dodge 2500.

 

[Stalking Light]

Sounds tight to me especially if you hit a bump.

 

[hebegebe]

I have been getting away with 3/4" to my storage basket without a hit for some time now. 1/4" seems tight but it's only a scratch if you lose

 

[Esus]

Maybe a thin layer of rubber or some stoppers on the bottom of the box to protect the truck? Probably not much room to add anything though running that short on space to begin with.

 

[buckland]

My box on the Tacoma overhang was an inch... very rough terrain and never any hit.

 

[camper rich]

I have started making a 1-1/2" riser to go under the camper. I will replace the 3/4" plywood with it so it should give me a net gain of 3/4" clearance. I should end up with 1" to 1-1/8" which should be plenty.

The box is 3-3/4" high and will hold my 8' telescoping ladder. The box and ladder together weigh 26 lbs. I already have an Easy Awn folding table mounted on the passenger side under the overhang.

 

[ckent323]

This is a great discussion topic and a good answer seems elusive if one is trying to minimize the distance (for wind resistance or adding a storage box etc).

It would not surprise me if the answer varies a bit across the truck brands and models.

FWIW: I did some web searching and it seems the typical minimum clearance given is 1-1/2" to 2" from top of cab to closest point on the over cab part of the camper. However, the range of opinions on this in various forums ranges from 3/4" to 5".

I suppose one could slowly drive over some large bumps that are representative of the worst case situation for your travels while a second person watches and tells you when the bed motion is largest and when to stop and measure the bed displacement relative to the cab. Has anyone done that?

My sense is that it might easily be 2" or more for some off road situations.

It would be good to see some actual measurements or calculations.

Craig

 

[ntsqd]

With the camper in place one could drive up an 'articulation ramp' until a tire starts to lift. as that would put the most static twist in the frame. Or follow Roger Brown's flat driveway, car-ramp test method to put the most possible twist in the frame. Either way will give some better idea of what kind of clearance your camper needs in your truck. It won't account for dynamic deflections, but knowing how close it can get statically should give you a better idea of how much added clearance is needed for those bumps.

 

[camper rich]

Not sure what Roger Brown's flat driveway car ramp test is, but I did drive my front wheels up on a 9" ramp, first the right then the left, and there was virtually no change in the clearance, still about 1". It could be do to the stiff frame on the Dodge 3/4 ton truck. The camper is over 1000# less than max payload. We'll be driving it to Alaska and I'm going to keep an eye on it if we do any real 4 x 4 driving.

 

[Bill D]

When I was washing my truck and FWC (with standard over cab clearance) this afternoon, I questioned how owners with such tight clearances wash the underneath of the camper overhang and the roof of their truck.

I find the underneath of the camper overhang is an area that gets dirty and shows the dirt fairly well. It also gets a few bugs.

 

[camper rich]

My Grandby has much more clearance than my old Ranger II, especially since I have a 1-1/2" platform under it in the bed. The only place where it is only 1" is under the front corner of the new box where I can clean it with a rag wrapped around a thin board. I can also clean it at a carwash with the nozzle pointed forward between the cab and the camper. I also have a Yakima wind fairing which blocks a lot of the bugs. Washing is really not a problem. Paste waxing it would be.

 

[rotti]

With the camper in place one could drive up an 'articulation ramp' until a tire starts to lift. as that would put the most static twist in the frame. Or follow Roger Brown's flat driveway, car-ramp test method to put the most possible twist in the frame.

Was curious what my clearance was.....3 1/2" and my "ramp" was the switchbacks on Redcone Mt/Webster Pass CO. No issues and yes the frames are pretty stiff on the 3/4 tons. If you look at the body panel lines they are straight.

 

[ntsqd]

Not sure what Roger Brown's flat driveway car ramp test is, but I did drive my front wheels up on a 9" ramp, first the right then the left, and there was virtually no change in the clearance, still about 1". It could be do to the stiff frame on the Dodge 3/4 ton truck. The camper is over 1000# less than max payload. We'll be driving it to Alaska and I'm going to keep an eye on it if we do any real 4 x 4 driving.

Check out this page:
http://www.4crawler.com/4x4/CheapTricks/Ramp.shtml

 

[OutbacKamper]

I don't think you need to worry about front to rear flex, but side to side can be a real issue. He is a Ford F350 at max flex:

Imagine having a camper in the box and the difference in over cab clearance from one side to the other. I believe that the F series trucks are more flexible than the GM and Dodge heavy duty trucks, so this is probably a worst case example.

I have about 1 1/4" at the closest point, and I am not sure it would be enough on very rough terrain: