Originally Posted by NoWhammies

So. My Garmin has the 'auto FTP calculations' feature enabled. Back in June I sent out and did a very hard/fast ride. At the end of the ride, my Garmin said "Congratulations! You set a new FTP record. Do you accept?". And yes, this was in fact a new FTP record for me because I knew what my old FTP was. So I clicked yes.

A few weeks later I was out for a ride. A fast ride, but nothing like the ride back in June. At the end of the ride my Garmin said "Congratulations! You set a new FTP record. Do you accept?" Now, this FTP was definitely slower than the one from June. So I clicked no. I then went in an doubled checked my Garmin FTP setting. It was the higher setting from June.

A month or so after that I was out on a fast ride and again. At the end of the ride my Garmin said "Congratulations! You set a new FTP record. Do you accept?" This FTP was again lower than the June FTP. But what the heck, I said yes and went on with my day.

This has happened a few times since. Sometimes the FTP is higher than what is recorded, other times lower.

Anyone have any idea what's going on here? The only thing I can come up with is the FTP calculation involves weight, correct? And I use my Garmin scale daily. So is Garmin calculating a new FTP for me each time based on my weight? Thank you.