18 miles to Bicycle Village for a tuneup: 15.4mph

My chain is getting old, my cassette only goes to 26, and I wonder about my bottom bracket. Time for a tuneup. I took my bike to Bicycle Village by way of a ride.

Haunted by my boss's phenomenal speed on similar rides (16.9mph), I started out hard and fast. Sucking air, I let off the gas when I crossed Havana after 20 minutes or so with only a 15.4 average speed. Not having given completely up, I started to make excuses:

• Larry is shorter than I am so he has less wind resistance.
• The height comes with reduced weight, so his energy makes speed, not weight move.
• My bike's old drivetrain (11 years) has such resistance it holds me back 1mph.
• Larry must be riding with longer cranks. Mine are 170mm.
• His bike as phenominal gearing: 34x32 to my bike's 30x26 (though soon to be 30x27)...and it makes him faster.
• His GPS has the wrong wheel size and erroneously calculates his speed.

I hope it's not incurable over training that's holding me back. I have another long ride with climb planned for Saturday.