Mounting flat bed

[kc0stp]

Alright as stated in another thread I finnaly got a new bed for my truck (took a while to find one I can afford) however it appears instead of drilling holes to re-use the factory bolts the designer of this bed instead just welded brackets to the frame/bed in the same general locations then cut them off flush with the bottom of the bed when he sold it (not the guy I got it from, hes selling it cause it wont fit the Ford hi-boy he has). So my question to you guys is would it be better to drill the appropriate holes in the flat bed and nut/bolt it on or grind off whats left of the old brackets (not looking forward to it...) and just weld new brackets in? Also going to have to add the appropriate spacers between the frame and bed to keep it level (figuring these are like every other truck Ive worked on where the frame under the bed isnt perfectly level) so what would you guys recommend for those? (seems most the ones around work just use wood but...)

 

[MIDNIGHT RIDER]

Without actually seeing both the under-side of the flat and the truck it goes on, that is a tough question to answer.

I will make one observation, DO NOT USE WOOD between the flat and frame.

I see several different trucks each day and see all manner of bad situations where wood has been used between a steel flat/bed and the truck's frame.

Wood is never a constant; it is always shrinking and expanding with the varying moisture content of the air.

Big heavy beds soon squish wood such that any mounting u-bolts, clamps, or whatever are rattling loose.

If the frame of the flat is close to the width of the truck-frame, then I suggest welding 1/4" thick X 6"-wide plates at the four corners of the flat, such that they will over-lap the truck-frame.

Try to orient these such that you can utilize holes that already exist in the truck-frame; otherwise, it is no big deal to drill new holes.

One big 3/4" bolt with BIG flat-washers through each of these welded-on plates and the truck-frame will hold things nicely.

Shim the flat to the distance above the truck-frame prior to drilling the mounting holes; thus, no spacers will be necessary, as the mounts will create the spacing necessary.

I hope I explained this such that you can picture what I am meaning.

 

[John Deere]

I don't recommend mounting a flatbed solid at all 4 corners if the pickup will be doing much off road twisting. I have broken several frames doing this. I have begun mounting the front corners in a floating design, and haven't had a frame crack since.

 

[kc0stp]

So are you guys just using the 4 corners or are you also putting brackets by the gooseneck/wheel hump? Details on the floating mounting?

 

[John Deere]

I'll try to take pictures of one of them tomorrow, easier than trying to explain it. As far as brackets in the middle, I find it generally unnecessary for most brands of beds, but some might need it you feel the bed isn't sturdy enough.

 

[justinray]

Ii welded square tubing to mine to stab bolts through, works so far.

 

[GOOSE]

Making it a dump bed would give you the floating design that was suggested.

 

[John Deere]

I've got a pic, but will post it tonight since I can't figure out how to do it from my iphone.

 

[90ididoorguy]

kco let me know if you need help i will give a lending hand to those in need.

 

[burt]

I look forward to seeing your floating design also. Where does the frame crack generally? I have a dumping flatbed on mine that I have oversized bolt holes on tabs in front. When I want it to stay down I hand tighten grade 8's through them. I'm loaded heavy off road a lot and have always wondered if I was better off using the extra rigidity of the flatbed or letting it flex. Any other insight on this you have would be apreciated.

 

[John Deere]

Sorry for all the mud on the mount, but we finally got some moisture last week. If you look at the picture you can see the idea is very simple. We use 7/8" or 1" bolts, the compression spring is tightened down to our personnal preference, which on this one isn't very much since the spring is a stiff one. We have one pickup that was set up using valve springs double stacked, but they seem kind of soft as the bed will occasionally bounce on that one. Under fulltwist (one wheel off the ground) the mount will open @2" which doesn't seem like much, but so far we haven't broke a frame since installing the beds like this. To mount the rear we have been bolting a plate along side the frame using the bumper mounting holes. Also I never weld mounts to the frame of the pickup, bolts only, My feeling is I am not giving a crack a place to start.

The frame breaks we have had using a solid mount are anywhere from right over the rear axle to right in front of the front mount to anywhere in between as can be seen by the pic of one of the retired pickups.

 

[kc0stp]

So essientially this but with a spring. what are you using the make the tabs to mount the bolt/spring to along with where to get springs? (sorry for 20 questions just want to do this right the first time)

 

[John Deere]

All the iron and springs came from my scrap pile. The mounts were made from I-beam, probably from an old steel building. The springs were cut in half and each half used on each side. I recommend walking through a machinery salvage yard and look for the spring you want. Really I'm not the one that figured this out, many boxes and beds that are mounted on medium duty trucks are done this way on all corners, we just felt that because we use ours to pull gooseneck and bumper pull trailers (the reciever hitch is integrated into the flatbed) the back needed to be mounted solid.

Really the design in the link you provided is a neat idea, definitly ideal for the rock buggy, I don't think I will use it on these beds I am loading 2 ton of hay on and pulling trailers with, but I will keep that design in mind for my own toys.

 

[John Deere]

Oh yeah, the question was made about using middle mounts. I don't know if doing that would hinder the the floating front mount. Really it's going to matter how sturdy you feel the bed is and how you plan to use it as to whether it is needed. My '88 is still mounted solid at all corners and has mounts over the axle because I didn't feel that bed was sturdy enough without them pulling a gooseneck trailer, and yes the frame has cracked on this pickup. I do plan on redoing the front mounts to float and leaving the middle mounts as is.

 

[kc0stp]

Well finnaly found the Ford body builders guide (obviously for newer trucks) and their current recomendations (with crash testing apparently) and their current recomendations are 3/8" plate on all 4 corners, 2 5/8" bolts through the frame (torqued to 60-65ft/lbs) and the bed side with a single 5/8" bolt and welded in place. The other caviat is that the front mounts are angled 45-60 degrees with the bed 3" behind the cab. Also mentions any spacers you use should be tapered to allow for frame flex.