Bed support rail dimensions
Thread Starter
Junior Member
Joined: May 2018
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Bed support rail dimensions
Hey Guys,
Need to pick up some square tube today to replace the two middle bed support rails. They were rusted to nothing, couldn't even tell how tall they were originally and the box is upside down at home in my yard so not convenient to measure the gap at the moment.. Anyone know what the dimensions are? Need height. I think it's 2 or 2 1/2" but not sure.
99 F-150 Lariat Ext. 4x4 Short box.
Need to pick up some square tube today to replace the two middle bed support rails. They were rusted to nothing, couldn't even tell how tall they were originally and the box is upside down at home in my yard so not convenient to measure the gap at the moment.. Anyone know what the dimensions are? Need height. I think it's 2 or 2 1/2" but not sure.
99 F-150 Lariat Ext. 4x4 Short box.
Senior Member
Joined: Jul 2015
Posts: 3,627
Likes: 795
From: Michigan
Rusted bed rails or "hats" as they're called in some places is a common problem. There are 5 rails and each one is a different length. I've replaced them a couple of times with 2x square tubing but never kept track of their dimensions. It's not necessary--within reason. It's also not necessary to use a thick walled tube. Anything over .060 - .080" is overkill and more difficult to work with. Rail kits are still available for 10th gen HD's and they will work but they are shaped a bit differently. Most notably the HD rails don't have the taper where they extend beyond the frame like some of the non-HD rails do.
If you go ahead with using square tubing put some weep holes. Depending on where and how you drive the ends can get plugged with mud and snow. Also if you don't plan on welding the rails on, use an old bicycle innertube to make some metal to metal isolators where you fasten them down at. If you can, go thicker for an isolator. 1/8" works great but it's not always easy to get your hands on. Use to be a rubber and plastic supplier here but they closed down about 10 years ago and buying slabs of rubber by the square foot went with them and buying by the roll isn't worth it.
Just remembered this, don't try to sandwich the new rails between the frame and bed. It's a PITA to try and pull it off. Neither the frame or bed will want to cooperate with you. Fasten the rails to the bed or frame first and then fasten the bed down. Also make sure however you do it that you can easily remove the bed and rails in the future. And while you've got the bed off, consider installing a panel over the fuel pump for easy access should you ever have to work on the pump.
If you go ahead with using square tubing put some weep holes. Depending on where and how you drive the ends can get plugged with mud and snow. Also if you don't plan on welding the rails on, use an old bicycle innertube to make some metal to metal isolators where you fasten them down at. If you can, go thicker for an isolator. 1/8" works great but it's not always easy to get your hands on. Use to be a rubber and plastic supplier here but they closed down about 10 years ago and buying slabs of rubber by the square foot went with them and buying by the roll isn't worth it.
Just remembered this, don't try to sandwich the new rails between the frame and bed. It's a PITA to try and pull it off. Neither the frame or bed will want to cooperate with you. Fasten the rails to the bed or frame first and then fasten the bed down. Also make sure however you do it that you can easily remove the bed and rails in the future. And while you've got the bed off, consider installing a panel over the fuel pump for easy access should you ever have to work on the pump.
Thread Starter
Junior Member
Joined: May 2018
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The answer was 2 1/2 for the two middle supports. I am using square tube. These are the ones that do NOT have bolts through from the bed.
I am welding them to the bed floor as were the original hat channel pieces.
Only the middle two 4' lengths need replacement. The others are fine. Bed is off already, so looks like an easy job. Also cleaned up the box and frame and painted with undercoat.
I am welding them to the bed floor as were the original hat channel pieces.
Only the middle two 4' lengths need replacement. The others are fine. Bed is off already, so looks like an easy job. Also cleaned up the box and frame and painted with undercoat.