Spam is considered to be "disruptive messages, especially commercial messages posted on a computer network or sent as email".
I realize that you are trying to drive traffic to your website. However, there are more subtle ways to do it rather than Spam a forum.
When you join a forum offer feedback on questions and valuable info rather than just suggest we visit your website.
Become a real and trusted member of the forum with your good advice.
Build up that trust over the months and years so that people have confidence in your advice.
You could also contact me in advance and inquire about whether we are open to Spam or not. Most websites disdain Spam. They view such postings with suspicion. In that case you are wasting your time.
Advertising your website the proper way takes time. It will not happen overnight. Only you can determine what sort of an online reputation you want to acquire.
Most Spammers are "hit and run". They post a few messages touting their sites and never return. I invite you to become a real member of my forum. Not just a one hit wonder.