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[PeteF]

"I do not trust GPS mileage because they tend to iron kinks in the road out"
A GPS system has no idea where roads are so how can it take kinks out? The accuracy only depends on the accuracy of the positioning which can, I admit be very variable.

[jefrs]

No, they don't know where the roads are, and that is rather the point. The military GPS systems we inserted into toys for the RAF and Navy log about every 3cm, practically continuous positioning, remarkably small devices but very expensive both in terms of money and battery consumption. Plus they use military satellite systems. The civilians ones like in my iPhone are lucky to be able to log every 10 metres and guess the rest on their gyros. They probably need three satnav signals, if they drop one they'll happily drop from 10m to 50m to 100m or more; if the road is particularly wiggly they'll draw a straight line between the log points; which is why the military ones log so often using about seven signals.

They're fine for A and B roads but if you go off piste you'll notice the GPS log doesn't tally with the map and the odo.

[pd110961]

2015 Enfield Classic, free flowing exhaust. me and camping gear. Derbyshire including snake pass, but no more than 50mph due to speed cameras. 84mpg!

[jefrs]

pd110961 - that sounds about right for cruising in top. Most of the time around here I'm in 3rd or 4th returning about 65mpg but have taken it on some longer runs on A roads returning 80+mpg including a fast run on the A4 west of Hungerford, despite being tweaked for (cof) performance. Pottering around town in 30-limits and the C&D back roads rarely gets it into top.

Both cars have been tweaked for 'performance', both are injected turbos, both return improved fuel consumption. The SUV with the 'stage 1' ran from here to Scotland without refilling, at motorway speed, over 30mpg when in stock form motor is lucky to return 22mpg used gently.



There will be a certain rev range where any motor is running most efficiently in top gear, it won't be flat out and most certainly not slogging it at slow speed. The SUV won't go into 6th much below 60mph and the bike dislikes 5th below about 40mph. There will be a happy rev speed where the motor feels unstressed and pulls freely, somewhere below maximum torque.



Air resistance increases with the square of velocity, so if resistance is 900 units at 30mph, it's 3600 units at 60mph, quite a large difference (the units are arbitrary, it doesn't matter what they are, for a given bike they stay the same unless you lie on the tank, fit an aerodynamic fairing etc). Up to about 20mph it's the mass of the bike, above that it becomes air resistance as the determining factor.