Hi Deltarider,
I questioned Mark, HondaMan, about this around 4 years ago. Below is what he emailed me.... I thought it was fascinating:
"Yes, the gap should be to the front. I've seen many manuals with the things reversed in the pictures, too, as well as on a lot of bikes. I always switched them when they came through my arena, though. The stress "lift" from the bump travel is designed to go up the rear edge of the fork tube, which should have the solid mount."
"I got this straight from a Honda suspension engineer in 1973 or 1974 in Illinois. He was helping us with the Production roadracing stuff, and was quite sure to point out to us that we had them both ways on the 4 different bikes we were using that day. We changed them all to the rear, at his direction. On some bikes (I think it was the CB350 twins), the front studs were shorter than the rear, which was further indication of what he was pointing out to us."
"When I ran the shape of the structure through a stress program (it was an early PC-based finite-element analysis program we used in the oilfield), it showed the shear stresses concentrated at the end-of-thread of the front stud when the gap was in the back, and vice-versa. Since the entire body of the fork tube is available to suppress a rearward-moving bump stress, it makes sense that the Honda guy wanted that extra strength "in the front" of the fork. The front stud has to bear both the initial impact and the rearward shear if it is tight, without gap. The program showed this load to be split between front and rear when the rear had no gap."
"Although, I've never seen one break in real life..."
Mark
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