I read on another forum that someone was getting an 2-3mpg increaces in fuel effenency with a top box on their bike so thought I'd try it on my Ten.

Well I'm pleased to say that I seem to be getting similar gains when I have the top box fitted compared to when it's not fitted for the same cruising speed. That works out at about a 5% gain, or reduction in fuel bill on the motorway. It also gives me somewhere to put my helmet if I go to the shops and an option to taking my Kreiga R35 rucksack with me (which I use on the motorway to hold my laptop)

At that rate the top box should literally pay for itself in 2 years (50k miles) for me.

Interestingly thats about the same gains as a 14 to 15 tooth change on the front sprocket (which would take about a year/25k miles to cover costs after you include speedo healer in the cost) but without the decreace in acceleration.

The free option of course is to just ride 5mph slower