I've actually tested a lot of these different tire sizes, properly, on a track, over accurately measured distances with scientific and recently calibrated instruments, and really, any difference you might find with any lesser testing is likely going to be pretty small if not completely inconsequentially tiny
AND potentially misleading; unless you
REALLY get down into the minutiae/nitty gritty of it all, and absofreakinlutely start matching the tiniest bits of the vast range of potential variables before doing the comparison, like having your tires before & after set to exact fractions of air pressure at a specific ambient temperatures running on a specific road surface that's a defined temperature at exactly the same time of day, cloud cover, sun inclination, et al)... And if you don't do this, then you'll likely either get some fairly useless data &/or just rapidly confuse/upset yourself and everybody around you, and you'll still probably only get results that aren't really valid enough to have any significant impact beyond your personal 'for interests' sake, but are also very likely going to different if not the opposite of what you might expect, and besides, because of the limitations in how you can measure/rationalise and include allowances for all the potential variables in your calcs, nothing's really 'exactly the same' &/or even 'correct' per se, let alone 'accurate' anyway...
Consider this - a taller tire that turns fewer revs per mile should theoretically give you better fuel economy, shouldn't it - travelling a further distance each rev? Yeah, but how did you measure how far you travelled in total &/or how much fuel you truly used?? If you used the speedo/odometer/trip meter on the Spyder to measure your speed &/or distance travelled, then because of the larger dia tire travelling further with each revolution than what it was doing with the OEM tire, the distance shown on your odo/trip meter will also have been changed too, so you can't compare it to your before calcs - it'll be reporting shorter total distance travelled over the same number of revs, cos unless you've reset them, your Spyder's computers still think you're doing 'x revs per mile', only you're actually now doing 'x minus some' revs per mile. And even if you think you've run over a given measured distance at exactly the same indicated speed on your speedo &/or GPS, there's discrepancies built in there too (even your GPS isn't really exactly accurate, altho it's likely better than your odo/trip meter, but then there's also variables based upon how many satellites it's acquired and how high/far away they are etc...) And then there's the pressure you're running in the (new, old, whichever) tires - that will vary its effective rolling diameter too, so there's more variance; and the new tire's 'revs per mile' is going to be different to whatever that was with the OEM tire, even more so if the barometric pressure is different today to whatever it was last week; so effectively, it all boils down to whatever you might think gain/lose in the way of fuel economy on the teeter totter, you'll likely lose/gain that or more on the see saw, &/or vice versa... And really, there's only ever gonna be 2/5th's of 5/8th's of a bee's whisker in it anyway -
IF you can rationalise &/or cater for all the potential variables!!
Yep, that truly is
a 'big IF'! 
