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As we are traveling to europe in a few weeks decided to buy a spare gates belt for our Calfee. While I was ordering went ahead and ordered a Krikit to check tension. After searching the web for the correct tension without success I called Gates. They told me the correct tension 45-60 but said if I had a iphone that their sonic app was more accurate. A cool app but not much application for a tandem except to check tension. Again set tension at about 60 mhtz. I was running ours at about 45 and we had it skip once on a very short steep hill that we didn't shift down on. Also very interesting to check tension at different parts of revolution as it varied by as much as 15 mhtz. Shows how non concentric the sprockets are on the spiders. You could probably try to improve that but may be a frustrating experience as both the captain and stokers would need to be dealt with. BTW replacement belt only $53, app was free, sending the Krikit back.