A 9" tread width would convert to a 230 MM tread on a metric designation tire. Here's the way the metric tire numbers are translated:

255: tread width in MM's (approximately 10")

70: Aspect ratio- - -the sidewall height is 70% of the tread width, slightly shorter profile than the original tire which was probably around 80%.

22.5: rim diameter in inches.

Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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