Does it have a notch it in? or square sides?
I had the one with the notch in, and man it fought me. I used this.
And did it on the lawn. I had to hit it so hard with the hammer to dislodge it that the chainwheel buried itself in the dirt lol. Thankfully it was steel (Mongoose 90s).
If it's the flat sided type you may need to put it in a vice.