So I was reading the "Just Bought a Brompton.... " thread below, and noticed a few mentioned the Brompton was rather inefficient. I was wondering if anyone else has measured for, and/or identified reason of, these inefficiencies?
My seat-of-the-pants estimate originally put my M6R pace ~15% slower than my CX/gravel bike (30 spd, 5 lbs lighter, tires of identical inflation and cross section width/height). So I was surprised to find that a few runs with a GPS on my usually exercise loops put that differential at half that (~7%, or ~1 mph). Not a bad sacrifice for the folding advantages, I think.
I'm guessing rolling resistance is pretty even between my two samples and I saw a driveline test putting the SA internal hub as efficient as a Shimano derailleur. I calculate the 5 lb weight differential to only account for ~1% on an average ride (equal parts uphill/downhill/flat). Clipless/30 spd vs half clips/6 spd may be worth a little bit too.
I think this leaves aerodynamic drag as my big difference, and so rigged an aero drop bar position for my M bars. Unfortunately, it was too late in the season for objective testing, but it feels significant based upon my ability to hold a higher gear longer. Some very dirty calculations (based on a wind tunnel article) may explain ~4% of my 7% differential. I'll need to wait til Spring for more objective side-by-side testing, but I'd really love to get within ~3% efficiency between these two bikes since they are my primary touring options.
Anyone else measure/analyze theses inefficiencies?
(Forgive me for the long and nerdy post, but it's winter, I've got cycling cabin fever, and just needed something to obsess over.)