First of all, make sure you get the Krikit II because the scale on that one is suited for the measurements required for the Spyder. The Krikit II will give you measurements in pounds (lb).
UPDATE : BRP put out a TST (Technical Service Tips) bulletin in June 2015 to all dealers that revises the specs for all Spyders for belt tension. I am fortunate to have a good dealer that provided me with a copy of this bulletin as I do my own minor repairs and adjustments on my Spyder. Here is what that TST recommended :
2008-2012 Models GS/RS/RT > Recommended Belt Tension > 270 N +/- 100
2013-2015 Models RS/ST/RT > Recommended Belt Tension > 630 N +/- 100
2015 Model F3 > Recommended Belt Tension > 300 N +/- 100
Now since your Krikit II measures only in pounds (lbs) and not Newtons (N) like the Gates Sonic Tension Meter that the dealers use, you need to know the conversion, which is :
Newtons (N) x 0.2248 = Pounds (lbs)
Pounds (lbs) x 4.4482 = Newtons (N)
The first conversion above is what you will use for the Krikit. So for example, on your 2010 RT, the recommended belt tension is 270 N x 0.2248 = 47.208 lbs tension ideal, or 170 N x 0.2248 = 38 lbs minimum tension, or 370 N x 0.2248 = 83 lbs maximum tension. You will probably never get it spot on, but as long as you are in the range between min 38 lbs and max 83 lbs, you will be ok. Also,
very important, as per the BRP Shop Manual, these readings are to be taken with the
back wheel OFF the ground,
at room temperature, and measured on the position of the belt in line with the bolt for the passenger floorboard or as close as possible thereto.
My 2015 Spyder RT Limited had an initial spec for belt tension of 1050 N +/- 100. I always felt some vibration at certain speeds/rpms and was starting to learn to accept and live with them. Now with the revised spec that I changed to, the 630 N +/- 100, there is hardly any vibration at all speeds, as I have tested the machine up to 100 mi/hr (briefly & safely of course). You should know that you will never get rid of all vibrations because it is the nature of the machine, with the long drive belt, but if you go with these revised specs put out by BRP, you can reduce the vibrations substantially and see an improvement like I did. I am sure BRP must have listened to all the complaints about belt vibration to warrant putting out this bulletin to all dealers.
Hope this helps.