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Foam quality... what the numbers mean?

5K views 6 replies 2 participants last post by  DanTwoLakes 
#1 ·
I am in the process of putting the interior back together on my 49 Ford coupe and need some seat advise. I started taking the covers off what I thought were decent original seats and found some problems. Apparently the seats have been out in the weather at some point in their long life, or at least the front seat backs have been. the rear seat and the front seat bottom seem to be fine, but the front seat backs are trashed. The springs are rusted to the point that they are not repairable. I'm thinking of junking everythig except the main outer frames and rebuilding seat backs using a solid foam cushion instead of the original spring setup. I'm thinking if I mount a plywood panel to the seat frame flush with the back I can build off of that with foam to create the seat backs. This will also let me put some more shape to the seat than it originally had. Maybe this plan is complete crap? I'm hoping someone will tell me if it is. But if it's not, my bigest question is what quality of foam do I need for something like this? I don't want my seat backs to go "flat" 6 months after i get my car on the road. The places i've been looking at foam (online) have a numbering system that sell foam by. Living far away from any foam supply stores how do I know what number of foam to buy without being to see/feel some samples?????

Thanks,
Jared
 
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#2 · (Edited)
The numbering system for polyurethane foam is very simple. The first two numbers describe the quality of the foam, and the second two numbers describe the density (ILD or indent load deflection) or firmness of the foam. The higher the first two numbers are, the better the foam quality is. The higher the second two numbers are, the greater the density of the foam, and the firmer the foam is. The first two numbers should be at least 22, with really high quality foam being 30 to 35. The second two numbers are as follows. 30 to 35 is medium, 40 to 55 is firm, 65 is extra firm, and 80 is hard. Back foam doesn't need to be really firm, or of very high quality because it gets very little wear. Seat foam, on the other hand should be higher quality and the density is a personal preference. 2235 would be good for back foam, and 3045 would be fine for seat foam. You can substitute a lower ILD foam for a higher one by making it thicker and wider and pulling it tighter. (BTW, the color of the foam does not mean anything, the only thing that matters is the numbering system).

There is a reason that seat foam is not 6" thick. The thicker it is, the more expensive it is. That's why they put the springs on the frame in the first place. The more open space and the less foam there is, the cheaper it is to make the seat. If the reat of the seat is O.K., why not just replace the back springs, which are the cheapest things in the entire seat system to replace? Back springs are usually 10 to 12 gauge (the higher the number, the weaker the spring is). Seat springs are 8 or 9 gauge.

You can put a piece of plywood on the seat back and build out with foam if you want to, but to reduce the weight you would add with a solid piece of plywood, and to make the seat back more comfortable , cut out the center of the plywood (leave a 3" border all the way around) and staple 2" wide elastic webbing criss-crossed onto the plywood which will replace the original springs, and still not be too stiff. Leaning up against a solid piece of plywood with foam over it would have no give and be uncomfortable after a while.
 
#3 ·
Thanks for the info. The elastic webbing sounds like a good idea. that would definately save some weight. I would just rebuild the springs on the current seat tracks, but it's more than just the zig zag springs that are bad, there are also large round springs that are all different sizes and the small springs that cross over between the larger ones tho tie them togehter. I will try and get a picture for you to look at tonight. I have found some foam in the number range that you recomended for about $60~70 for enough to do my seat backs. I'll get you a picture and hopefully you will advise me further from the pic.

Thanks,
Jared
 
#4 ·
here is a picture of the seat back in question....... The picture didn't turn out the greatest. but the springs are pretty much all junk in my opinion. If I do use the plywood/elastic webing method you talked about as a base for my foam, should I put some thin panel board or something on the back of that so that the foam and bands don't show through the back of seat?
 

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#5 ·
You're right, those springs are pretty well worthless. Screw or bolt ( bolts would be best, and be sure to countersink the bolt heads) the plywood frame on the back of the old seat frame towards the rear of the car. This has the added benefit of making the seat frame stronger. Staple the elastic webbing on the front side of the plywood towards the front of the car. Then you need to pad the back of the plywood frame before you pull the cover over the new foam. Be sure you sand down the outside edges of the plywood frame just enough so the edges are not sharp. If you want, you can staple the fabric onto the plywood frame instead of sewing the seat back all together and pulling it over the frame. Then cover the seat back with an upholstered panel, just like a door panel. The early 60's Mustang seat backs were done like this with a panel to finish them off. If this doesn't make sense to you, just ask more questions.
 
#6 ·
That all makes pretty good sense. Once I strip off all the springs I will be left with a round tubing "hoop" frame. I think I will inset the plywood flush with the back of the frame. that way the material will not have to go over the edges of the wood, it will just go over the steel tubing frame just as it used to. The panel insert on the seat back is a great suggestion. I would think that would make the covers easier to get on for sure. Have you ever had any experience with "whisper" vinyl material. I found a local source for that brand and it would sure be easier to buy it local than mail order material. Espescially if I need to go back and get a bit more if I run short. It feels real nice and is somewhat economical. But this is my first experience with interior work. I'll try to post some more pics of the process as I go just in case anyone cares. Thanks again!
 
#7 ·
Yes, Whisper would work fine for you. I have never used it for a car seat, but it's one of the many vinyls I have access to through my local suppliers and I have samples of it. It seems to be a nice fabric.
 
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