We Have No Idea question

Ignore the book title. I read a book in middle school. It started off with someone timing themselves on a bike. I think it might’ve been summer. There was a crawl space under a porch involved. This is where it gets complicated for me. I’m not sure if this is a separate book, or if they are the same book, but I remember some boots being stolen from a yard sale. I also remember sneaking into a spa that was full of the enemy, it might’ve been pyramid shaped. I have been looking for this book, or books, forever and can’t find anything on it online. Nothing that rings a bell anyways. If I saw the cover art, I would know for sure. Please help.