I will be arriving in ORD on LH (LH403 from FRA) at 12:50 and want to catch UA147 to SFO at 3:15pm (no connex, two separate tickets)
Is 3:25 enough for customs + immigration (non US citizen) and is there any chance of staying inside security and avoiding beeing checked twice?

Thanks!

Your layover is only 2:25, not 3:25. I would take a later flight if I were you.

<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by iahas:
is there any chance of staying inside security and avoiding beeing checked twice?</font>

No. You will arrive in terminal 5, which is separate from the UA terminal. After clearing customs, hop on the free shuttle train to the domestic terminals. The United terminal will be the third (and last) stop. plan on 15 minutes for total shuttle transit.

Are you a "star gold" with the star alliance?

If yes AND you do not have a problem with rushing you should be able to make your connection with 2hrs 25 minutes. As there is a prefered line for star gold members at ticketing and going through security.

If not, I would take a later flight.