is polyester resin okay for producing front bumpers?

Is there an additive to make it more flexible?

Yes you can use it to make bumpers. Why do you want to make it more flexible?

yyou can buy a flexible poly resin, don’t know where in your part of the world though. a lot of drift kits are made using it.

What type of resin would you suggest for carbon fiber bumpers and fenders? I am curious because I want to make some for my car and a friend of mine’s car for auto-x.

It’s a question like what kind of car do I need to do groceries. It depends on what region you are in, budget, manufacturing proces, UV or no UV protection needed (clear coat after), ect.

id have to say that for autox you are probably going to crash anyway so use something cheap. as for uv, parts will probably need repairs before this becomes an issue. not trying to be a dick but being realistic.

Not much crashing in auto cross. It’s where you race time trial cone courses, no head to head.
The only reason to replace stock bumpers on an auto cross car with carbon fiber is weight. If you use poly resin and worry about durability then the parts won’t be any lighter than the OEM plastic parts. You need. To use lightweight epoxy and the thinnest canon layup you can get away with or don’t bother. If you just want to make carbon fiber parts for looks, then don’t bother autoxing and build for the shows.

Yeah the bumpers would be a prototype kind of thing but fenders would help a lot for weight and looks.

normally a good quality poly with a skilled lamniating results very flexible bumpers.