I recently changed the domain for a Rails app I have running on Heroku. I redirected the original to the new one, and for the last couple of months have been running SSL on
In addition to what Jan said, here is what I did to do the trick.
In application_controller.rb :
before_filter :expire_hsts
[...]
private
def expire_hsts
response.headers["Strict-Transport-Security"] = 'max-age=0'
end
In production.rb
config.force_ssl = false
Clear the cache of your web browser and that's it !