Originally Posted by
reburns
I have used the method of strumming the belt and measuring the tone frequency at various rotation angles to find where the belt may be tightest, then simply loosened the ring bolts and retightened to get the tension fairly even over the full 360 degrees. I shoot for roughly 40 hertz, plus or minus. All very crude compared to your analysis. But I have yet to replace a BB since switching to the belt, although I did have to replace one when we had a timing chain.
I agree with others that the Gates recommended tension is way higher than necessary.
Are you sure the two rings are perfectly aligned, and neither is bent causing some of the axial runout you are measuring?
I have never had luck with the strumming method. I would get 40 hz, then 25, then 80, then 40 again, then nothing,... Maybe I don't know how to strum a belt? (you must also understand that I am as far from being musically inclined as one can be and still fog a mirror).
I am confident that the rings are flat and true. I laid both of them on the cast iron surface of my table saw which is pretty flat. Both rings where true and flat. I used the dial indicator and indicated the axial alignment of the crank spider arm surfaces of the crank that is way out of alignment and the surfaces are out consistent with what I measure on the ring when it was installed. This tells me that the primary condition is that the crank/spider is not perpendicular to the crank axle. I think that this is a deficiency of the timing crank design where the timing side crank is bolted to the splined end of the crank axle. I don't know how to control the perpendicularity of this interface without a machined flat surface on the axel to hold the crank arm against. This does not exist so it is what it is.