If it is a uber expensive bike, do not lock it up, take it with you. Thieves are clever. I remember going to a hardware store in the 80s and a very expensive Kline aluminum bike was lock to a sign post. Kline bikes at this time were handmade, thus expensive. After I came out of the hardware store I saw a guy standing where the bike had been looking lost. I had a feeling he was the owner of the bike and that it had been stolen. I saw the guy and sign post but no bike. The thieves stole his bike by un-screwing the nuts/bolts holding the post to the base. Learn from his lesson.