I know mine isn't that far off. Can't explain the particular variance, just know it is there. also your RPM's would count on if it is level, head or tailwind, weight, tire wear/pressure amongst other variables.
You could probably drive yourself crazy trying to keep these set to go "On th Pipe" Easier to just leave well enough alone or just do a minor tweak to the rollers. I think the claim with 20x12 14GR Dr Pulley sliders is 1/2 second off 0-60 times and no top speed hit or even an increase somewhat.
So again for myself if I decide to get the rollers it will only be a mild switch to those Dr Pulley's. We will see how things go as the miles get to 3,000 and I add a top box...............
Edit; also remember the GPS is set to read speed at 100% level. When you go up or down hill the distance actually increases slightly so if the hill were 10 degrees then actually you need apr 61 MPH for the GPS reading of 60 MPH. at 15 degrees you would need 62. 20 degrees 64 MPH etc. And that assumes their accuracy, consumer GPS's are never 100% accurate either. So a GPS is not always the best judge of speed just an easy aproximation.............
Now remember we are 100 LBS lighter than a Suzuki Bergman 400 but look at the link below
http://piwyr.co.cc/topic/2473106/1/And yet another link to tease...................
http://www.downtownitalia.it/index.php?option=com_fireboard&func=view&id=12898&catid=10&Itemid=59
