I missed 8 days so I wanted to ease back in with my knees and back hurting I didn't want to make matters worse. I took out the Race bike because I changed the head set stem length from 100mm to 80mm. So it was a test ride to make sure it was OK. I get out and started out easy, but thought I was feeling good and my speed was much faster than I intended but it felt easy so I went with it. I was on the race bike so I thought it was the bike. I get to the 1/2 way mark and heading down hill but my speed was not as great as I thought it should be and I was laboring to keep it up. I hit he bottom of the short small hill and now I had to work to maintain speed. I soon realized I ad a tail wind and now I was going into a head wind so I wasn't feeling as great as I thought, I was being aided by wind! Now I had a nice average going so I wanted to maintain it so that meant i would have to really work. for the next 4 miles I lost 7/10 of a mph on my average, between the wind and a small 1/2 mile hill got the best of me. I decided to put the hammer down to make up the 7/10th which meant wind or no wind I was going to get serious. I made it all back but lost 1/10 on the 1/4 mile slow down into my neighborhood, pot hole filled and sand road. I didn't want to have a accident trying to keep up the speed. This wasn't a smart ride as my left knee hurt so bad after the ride i could hardly walk, Had to take off the next day and take some meds for swelling and pain.