Every time I have someone help me set the race sag on my bike, they tell me to stand up, but if I am standing up, they tell me to sit down. What’s the proper way?
It doesn’t matter. That is not to say that the measurements won’t differ, but since your plan is to ride the bike after setting the sag, you will be the final arbiter of whether the sag is too high, too low or just right. Measure the sag however you want, but once you find the perfect number, always measure the sag using the same method. The stand-up method does eliminate the variations of where you sit on the saddle. If you sit even 1 inch farther back than the last time, the sag will change.