I have a set of BMR boxed sub frame connectors bolted up to my 95 t/a and have always been kinda bothered by their weight. It’s not such a big deal since my engine’s a 396 but I’ve always wondered if a lighter set could be constructed. My question then is what materials would you recommend for making a light weight set of subframes? I’ve toyed with the idea of having a carbon fiber set made locally but reconsidered after the welding issue, even though I myself have only bolted the BMRs. What else could these be made with barring astronomically expensive space aged materials?

 

If you go with the tubular... they're a bit lighter. If you wanted to make your own and wanted lightweight, use 4130 chromoly (and a thinner tubing) and stay with the tubular design.

-Mindgame

 

Well carbon fiber would be nice But you dont want to ever put a jack on it ..Also it burns rather than welds..

Crhomemoly steel is a better choice but it has its own drawbacks..1st off it has to be tig welded onto the parent metal..It has a higher melting poinmt than mild steel to keep it simple. Also from a very rarely looked at standpoint, its not the best choice to connect two parts of a mild steel car together.With most aftermarket subframe connectors they become a 3rd member of the chassis..They are attached to the ends of the front and rear sections all the while the roof line and floor line are still working the same..On a few cars that ui have seen at some shop seminars there was actual cracking of the unit body from this..Depending on the type of structure it is said that the floor will fight the subframes and the roof during hard loading..In a street car this is a lot more than just stomping on the gas..You have road irregularities and stopping and turning just to name a few...A way to combat this is to build through the floor connectors. Made popular by a few Jersey stang bangers and proven on nitrous petes cars they seem to work best..I like this design myself as it actually makes a real true frame from the floor rails of teh car..Still your issue of weight isnt addressed..I must say that this is an area that a few lbs wont make that much a difference..Buy some bogarts instead of welds..A few lbs of unsprung weight 4 times less than sprug weight..

Albeit a far better metal than mild steel it is at the same time of different composition..Your trying to tie toegether two ends of a structure..The best way to due such with longjivity is to use the same mateirial..Now some may say (including myself) that its better for a cage or even a bar but thats a whole nother reinforcement metheod and thus another topic..Chromemoly can be of thinner wall thickness thus the lighter weight but on a streetcar i cant see it mattering that much to save about 5-8 lbs when comparing the two.