Review on Gates 91107 Krikit V-Belt Tension Gauge, Black - Accurate Belt Tension Measurement Tool for Automotive Maintenance by Mike Kimball

I had high hopes for this. The trick is to place the device on the strap (with the small plastic tab all the way down on the "high voltage" setting) and then press on the pad of your finger until the pad "clicks". This requires a prescribed force of 22 pounds, and the black "tongue" measures how much the belt flexes under that pressure. There is no need for a second hand holding up the ruler to determine how much deflection has been created at a given pressure. The disadvantages are greater. First, it takes a lot of practice to get stable readings. You need to make sure you place it squarely in the middle of the strap's span and use enough force to "click" it, nothing more. You must also ensure that the "non-read" end is in full contact with the strap without putting any pressure on the device, except for the finger space in the middle. I couldn't get a stable reading after a dozen tries, so I switched to a piston type. Essentially, however, it appears that this type of measurement is inherently limited to a small range of belt spans (since the same tension over a longer span will result in a "higher" reading as the belt flexes more). Which is good, but I haven't found anything in the manual to confirm this or give the operating parameters under which this would be accurate. I think a little "tighter" in the black "tongue" and some of those issues would go away. a way. If the black tongue had a little more resistance, the other side of the pressure point would have a harder time detaching from the strap. However, I am concerned that the measurement is simply not physically tenable as a function of actual measured belt span. I think with practice your strap will be "about" the right tension. This is probably a lot more accurate than the "thumb test" your mechanic uses, and with a lot less trial and error.