I did an unsupported century last year on my 30 pound "shop" mountain bike. The first 55 miles were easy but the last 45 or so were pretty horrible.
This year, I want to try it again but with more hills. I really don't want to lug my 30 pound mountain bike up the hills, but I don't have the money for a decent road bike.
If I follow a reasonable training plan on my 30 pound mountain bike this year, will I be "safe" moving into high-dollar 15 pound rental road bike 24 hours before an unsupported century?
WARNING: This question was edited from its original version. It originally used the term "homemade" century to denote an unsupported century. Also, the question originally asked if it would be okay to switch to a road bike the day of the mentioned century. Now, the question asks if it is safe to switch 24 hours before the mentioned century.