In July of 2023 I got a new Trek AL 5 and go the usual accessories with it. Bottle cages, seat and cycle computer. It is a Bontrager RIDEtime and was set up by the Trek bike shop. On my 1997 Trek 1220 I had set it up myself using the roll out wheel size method. This time I figured with a bike mechanic doing the set up he would get it as accurate as possible. My mistake for making that assumption. It is a wireless unit and I didn't want to try and fail setting it up myself. Fast forward one year. I have. been questioning my speed on the new bike compared to the older one. Am I just slowing down a lot faster than I thought I would at 76 years old? Or would the rollout method of wheel sizing be better than the wheel chart? The wheel chart says for a 700 x 32 wheel the setting is 2190. But the roll out method comes up with 2140. I have changed it but haven't ridden yet. Will the 50 mm difference matter on speed and how much difference will there be on a ride of twenty miles. I am not a math whiz so I don't know how much difference it will make. I tried doing some calculations and couldn't really get anything that sounds logical as a result. Anyone have a quick calculation that might show me what I should expect with the change? Thanks.