Help with bicycling goals?

Hi guys, I've recently been trying to get back into biking (something I did and loved as a kid/tween, am now 34) and I realize I've been really bad about trying to make goals. I'm hoping some more experience can help me make more realistic goals -- namely, I'm in an 8 week challenge and I want to have some idea of what I should shoot for at the end of the 8 weeks.

To get of an idea of where I am, I started biking all the way back on March 3rd. First I used the recumbent bike, doing about 7-10 miles in 30-40min. I recently graduated to upright stationary bikes, and have been doing 14-15mph of a cross terrain circuit for 40-60min like 5 times? This stuff is pretty new to me.

Anyway, my main 8 week goal was to ride a local creek path from the south suburbs I live in down into the main city, a 16-18mi trip. Today I did that, but I meandered over to a favorite park for some lunch I'd brought, so it ended up being 19.22 miles. The derailer has issues and will need professional attention asap.

This was the last day of week 2 of the 8 week challenge, and now I have no idea what a realistic goal for week 8 should be. Any ideas? The total length of that trail is 28.5 miles one way.

Thanks!

Replies