I have the store bought speedster bucket seats. For the butt pad, do you use upholstery foam or do you use coil springs with foam?
4 inches of foam
And THAT prompts another question! Only because I worked for a fellow once that had a son who was in the foam rubber mfgr. & sales business, and one thing I learned was that there are many, many grades, densities, qualities, etc. of foam rubber. (....or foam "whatever"). Always have to wonder what quality of foam you are really getting, because it may or may not be satisfactory when first "installed", or, it may or may not "REMAIN" satisfactory over "the long run". I've had what seemed to be decent foam rubber initially, turn into actual "powder" in a very short period of time. I'll bet everybody who reads this has experienced, for example, foam rubber-backed throw rugs where the foam backing soon disintegrated! And to this day, I STILL don't know how to determine good quality foam; I guess you just have to deal with a reputable supplier! I do know that to a large degree, the better the quality, the more it costs! FWIW,......harold
The best foam i have found is what is used in a camper for the seat cushions or beds
I use the thick green foam from Joanne fabrics. The easiest way to cut it is with an electric knife. I have some of Paul's camper foam in reserve - Thank you Paul.
Ive played with seats for a while and if you drive alot like I did the green foam goes flat. I ended up hacking apart a rear seat from a car and glueing/using that foam to make for a comfortable seat that would support better.
I gave up on plywood seat bases years ago. I made a tube steel frame, then wove burlap strips to support the foam... Worked great!! But eventually stretched out. Since then I replaced the burlap with rubber bladders out of a MGTD... Going strong and super comfortable!! 200 mile endurance runs?... No problem!!!
I have used temporary cushions that had foam in them. I do not use modern foam in my speedsters as a permanent thing. What I do use, depends upon the car and how thick I can tolerate the seat. The boat-tail has original era seat springs in the bottom, thick felt in the back. And I like it that way. A couple of speedsters I have had had a pile of felt in the bottoms. Maybe I am a h@&d-@$$, but I never had a problem riding all day in them. Although, a few passengers have complained.
Be sure to add a four inch angle iron bracket to the outer sides to keep it from bending over. 3/16 inch thick to be sure