Weight, Weight, don't tell me (that it matters that much)!?

Ok, I guess you'd have to be an NPR listener to get the title spoof.  Anyway, my point is I rode my light weight bike today.  No real reason, just was bumbling around the house last night and felt bad that it was dusty.  Now light is a relative term....my road bike is a Cannondale Synapse from 2008(?) (back when they were made in the USA), so it probably weights sub-20 lbs.  However, when compared to the Salsa Fargo loaded with fenders, frame bag, seat bag, rack, etc......it's light.

 vs.

My question is how much of a difference does it make.  So here's the two rides (just going to work...aka downhill).  Not really that different.  If you look at the moving speed...the road bike is just 1.7 mph faster (moving speed).  And you could argue I knew I was doing this comparison....so I might have been going for it a bit.

The real test is really how the weight will affect the climbing performance on the way home.  There's no doubt its easier to roll less weight up a hill (darn physics).  My question is does it really matter on a 11 mile round trip commute in terms of time / effort.  I don't think so, but we'll have to see what the numbers say tomorrow.

Cannondale Synapse (light)

Salsa Fargo (heavy)