Crashed, I must say that I did have one particular set of 16/61 that went on for a while but finally the 61 stripped.
As for the smaller 2nd gear pinion, that's what I used anyway. Always 16/21 and 61/57. So I don't think that
s the issue. I think Julius expalined it best ... its got to do with the 16 teeth being on a larger than ideal/optimum diameter.
I just looked again at my new set of pinions and gears ... when the one tooth is perfectly centered on the spur, the next tooth on the pinion is actually not quite in and "rubs" a lot as it tries to engage the next tooth on the spur.
One can imagine that at high speed, AND when the pinion teeth is sharper, the tooth will bite into the spur tooth and starts the stripping sequence.
This therefore explains Pyramid's solution of meshing the two as lightly as possible but moving the engine further forward. Remember ... his mode elongates the engine mounting holes towards the front of the car.