Comparative fitment isn't as simple as the charts I've created suggests. Manufacturers tweak the tyre sizes considerably, more than the standards really allow them to. Tyres sold on the metric/universal standard vary much less than the old Imperial measures. Nevertheless, a 1/4" or more variance between manufacturers of the same universal tyre size is still common. In the older tyres, the ratios of tread width to tyre height were almost proprietary and ranged a significant amount, perhaps as much as 20%. Even within a single manufacturer, tyre aspect for standard rating versus, high performance versus super high speed ratings also differed by up to 5%.
Having said that, the chart is still a fairly accurate comparison using the theoretical standards as a guide. The fitment chart should be used as a fairly accurate starting point, but, any given tyre can still vary from the standard measures provided.
Please note, on the 400F, the suggested tyres were Imperial, S rated tyres. Hence, I have updated the chart, replacing the previous H rated with S rated measures where it made sense. (S rating comes with a higher aspect ratio on average than H rated tires.) Also, since wider seems to be the rule, I have not included tyres that are narrower than Honda's recommendation.
Bob (or any other moderator), I'd be glad to create a series of fitment charts for the FAQ, if that is something that might help.
