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Sorry to beat this topic to death, but adding my subfloor tomorrow/Saturday and want to be sure I'm on top of everything.

After reading a lot of posts on here + elsewhere I'm going with 1/2" pink polyiso (Owens Corning) and 3/4" maple plywood (this plywood is beautiful stuff). Plan is to use builders paper to make the template, cut the polyiso to the template, test the fit, cut the plywood to the polyiso template, and then lay both in there without adhesive. Last step would be to bolt the plywood to the 8 tie down points and add self taping screws if I feel they're needed. The tie down bolts is where my question comes in...

I just undid my tie down bolts earlier today and after going around to hardware stores I wasn't able to find anything similar except for hex headed M8 bolts. Are these what other folks use? I'm thrown off as they're larger heads than what I unscrewed and I figure it will cause issues with things being flush on top of them if I use these hex heads? Am I overthinking here? Is the 50m size what I'm looking for?

Also, while I'm thinking about it... folks mentioned using painters paint on the edges of the polyiso (I believe I'm making this up). What is that for? Is that recommended or overkill?
 

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I was fortunate to find Sprinter tie-down cups on eBay. IMHO, they are the best solution, particularly by the slider.

I don't understand why lapping and gluing is not more common. It is ridiculously easy to do.
 

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I was fortunate to find Sprinter tie-down cups on eBay. IMHO, they are the best solution, particularly by the slider.

I don't understand why lapping and gluing is not more common. It is ridiculously easy to do.
With your lap and glue, did you go in a half an inch or an inch? I may give that a shot. Thanks!
 

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was going through your build blog...saw that you used the factory rubber mat as the first layer of flooring, i'm planning on doing the same -- have you had any issues with it? i wouldn't expect there to be any but just wanted to check. thanks in advance!
 

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I used Bed Rug Van Tred Mat for base and then 3/4" plywood and the below bolts from Amazon. I did not glue or join the three pieces of plywood flooring in any fashion- it isn't going anywhere.... you will be bolting through cabinetry, battery and refrigerator, water tank framing, etc and through the van floor in many locations. I will be using vinyl plank flooring left over from a house job over the plywood.

Depending on what type of flooring you end up with and the direction you run it compared to your plywood subfloor joint you may want to fasten them in a fashion as MsNomer has described.

 

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I don't understand why lapping and gluing is not more common. It is ridiculously easy to do.
Maybe it's because some of us are complete noobs at woodworking and don't know how to accomplish this task. With a router maybe, or with that dado blade I don't have, or a table saw and a chisel, or ??? These are big sheets of plywood which always seems to complicate matters too.
 

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I used 3/4" polyiso under 23/32" tongue and groove OSB subflooring held in place using hex head M8 bolts countersunk with a 1 1/2" forstner bit. Obviously time will tell how well it works, but it feels remarkably solid. Most of the countersunk holes will be hidden under cabinets and the odd exposed one will be easily bridged by vinyl plank flooring. I'll be getting some tie down cups for the rear garage area. The bikes will be held securely by the front axle locking mounts but I want extra tie downs for the odd stuff that tends to float around.
 

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Maybe it's because some of us are complete noobs at woodworking and don't know how to accomplish this task. With a router maybe, or with that dado blade I don't have, or a table saw and a chisel, or ??? These are big sheets of plywood which always seems to complicate matters too.
Router is the easy way. With big wood, it's often easiest to take the tool to the wood.
 

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I know this is an old thread, but it's the most recent one with info about the tie-down bolts, so I hope someone can answer my question...

I removed the tie-down bolts in the side rails of my van, and want to replace them with regular bolts to support rails for my bed frame. I've tried 5/16-18 and M8 bolts, but they will only go in a few threads before getting super tight. I know the original bolts had an odd cutout - like scoring parallel to the shank of the bolt - on the first few threads but I didn’t think it would affect another bolt going into the threads on the van. (I hope this makes sense!) Do you know if they require some super-special bolts?

Thanks so much, Carrie
 

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I don't think they are super special but make sure they are M8x1.25. The thread pitch will affect that greatly. That said I ended up not using the factory tie down locations so take my insight with a grain of salt. I did remove them a few times though.
 

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You should be able to find them at a big box store. Bring one with you and test it on some nuts then get the proper bolt. Scalawag is correct when he says M8X1.25 pitch
 

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To keep things flush consider using flatheads like these, not a terrible idea to use stainless since these are exposed to the elements under the van:
 

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Yeah, realize that you can only gain access to maybe 4 of the tie down bolts from under the van, so you won't have a chance at sealing them from the bottom if you don't use stainless.
 

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Jumping on this thread because I'm having issues getting my subfloor to lay flat and trying to figure out if I need to add more bolts through the middle of the floor of the van in order to mitigate this (sheets are concave and form "bubbles" and create high gap between the sections). I'm hesitant to drill holes through the metal floor...and I liked @MsNomer 's idea of lapping and gluing the plywood sheets, but can that be still done easily enough if they don't lie flush together? I was hopeful that having a heavy set of drawers and a battery on the back wall of the van would be enough to keep the floor flat and stable in supporting a floating hardwood floor of T&G panels, but now I'm feeling doubtful...any help anyone can offer would be SO appreciated!
 

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What did you use for your subfloor? There is a vast difference in quality and suitability for subflooring. I’m assuming you haven’t put anything on it yet - is that correct? I used ¾" poplar plywood and it’s quite flat and heavy. I’ve only held it down at the existing tie down locations. I used wood biscuits at the joints along with wood glue. I don’t particularly like the idea of screwing or bolting they the metal floor for many reasons and it should not be necessary other than perhaps in one or two places at the most. You must use solid core flat, good quality plywood to begin with or it will never lie flat. If it goes in warped it will most likely never really be truly flat. The factory floors are glued down but if you plan to insulate under the subfloor, as you should, it becomes pretty much impossible to glue it down. Some people swear that ¼" plyscore is good enough but I personally feel ½’ quality plywood is the minimum one should use and thicker is far better and doesn’t really cost much more in the long run.
 
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