7 Inch Discharge Curve

I've been busy working on some Wardriving hardware and might blog about that soon. I've also been helping test an Android ACARS decoder application and might blog about that soon.

But in the meantime, I finally fitted and balanced the low rolling resistance 7 inch tires for Miss Linn and like always, I had to quantify just how much (if any) more efficient they are vs the current 8 inch all purpose ones I've been using the most (not the 8 inch off-road wide ones I've been enjoying of late).

Let me just say up front, that I really wish I'd had made better notes of exactly what Dan said about testing the 7 inches, my memory is something along the lines of .... "Don't bother, they won't be any different"....

The idea was to try and do the same ride in much the same conditions as the last discharge curve test ride.
You can read about that ride and the resulting data here if you missed that one.... It really is riveting reading!

It was surprising just how similar the two days were.
Same temperature, same soft breeze from the same direction.
I also made sure to hold the same rough speed of 20mph.
Made sure to do the same annoying stop every 2 miles to photograph the data.
I'm glad that I log each ride with the Garmin watch / app, it really helps tie these sorts of tests together for me.

Out and back along the river. Same 26 miles.

Here is the graph.

For reminders, the 8 inch tires:
0.64Ah per mile.
The 7 inch tires:
0.588 Ah per mile.

Here is the voltage discharge of the two tires on the same graph.

There is nothing special about those first 2 miles. I think it's just a case of the battery coming off the charger in the garage and hitting the trail about 20 minutes later. The 'fresh charge voltage' level just evaporates pretty quickly and the battery settles into its bulk reserves.

At the end of the day, while the 7 inch sneakers are 8.3% more efficient, we are only talking about an extra mile or two of range, not the 10 that I'd like to pick up (somehow).

Nagging thought:
I don't know where the slight improvement came from, the lower rolling resistance, or the fact that the motors are doing a higher RPM for the given road speed and thus might be in a more efficient part of their power curve - or perhaps it's a combination of both.The big difference for the human on the board is that they are a LOT smoother. The ride is really sweet as a result.
So, I guess if my long ride(s) is on good ground and I don't need the 1 inch of ground clearance I've lost, it's a no-brainer to do long rides on the 7 inch wheels.
I wonder what range I'd get out of 9 inch wheels?