Painting nose cone, rear bumper etc. ?

[The Seer]

Soon I’ll be painting the nose cone and rear bumper.

I’d like to use Upol 2025 high build as a primer surfacer (not sure if that’s available in the USA) more to the point is a specific primer needed for these urethane parts?

Thanks

 

[The Seer]

...I'm guessing these urethane parts require a flex additive mixed in with the primer, or is there a ready mixed primer that contains this?

 

[Twisted_Metal]

Some people swear by a flex additive but I don't think it's necessary.

If you smack the flexible bumpers, you will most likely incur damage whether it has the additive or not.

Make sure the urethane parts are primed with the same color as the rest of the car.
Some top coat colors will not hide a primer/sealer color variation between adjacent panels.

 

[ZsZs]

SPI Epoxy primer claims that no flex additive is needed. I went with what they claimed would work. Time will tell.

 

[The Seer]

Some people swear by a flex additive but I don't think it's necessary.

If you smack the flexible bumpers, you will most likely incur damage whether it has the additive or not.

Make sure the urethane parts are primed with the same color as the rest of the car.
Some top coat colors will not hide a primer/sealer color variation between adjacent panels.

I agree, if there's any collision or impact both primer and top coat are gonna crack. However I did wonder that potentially with extreme temperatures that there could be some expansion and contraction in the material and thus possibly a flex additive may help reduce the risk of cracking? Just a thought

 

[The Seer]

SPI Epoxy primer claims that no flex additive is needed. I went with what they claimed would work. Time will tell.

I'd believe that too. From what I've read epoxy primer is pretty darn flexible, I don't think you'll have any issues there. The only reason I'm not using my Lechler 29107 epoxy primer is that it doesn't like being dry sanded (and I was advised not to wet sand) at 500 grit. Clogs the paper and then scratches the surface.