Posted by Matt Wilson [108.162.221.211] on Wednesday, June 28, 2017 at 19:08:13 :
In Reply to: No truck was orginall equip, with 4,89s and 7,50 posted by Clueless [162.158.122.39] on Tuesday, June 27, 2017 at 23:59:54 :
Ok, so your speedo was set up at the factory for 4.89 gears and 7.50 x 16 tires. That's opposite of what I was thinking.
I don't know what the rolling radius of a 7.50 x 16 should be, but a quick look online indicates that it may vary between 15 and 16 inches. Assuming that's correct, and taking the average value of 15.5" as representative of the tires originally on your truck, and for which the speedometer was set up, then the speed with 9.00 x 16 tires would have been about 62 mph. I'm not that familiar with 7.50 tires, but my estimation of the rolling radius seems a little small, so I don't know if I'm coming up with reliable numbes or not. Also, as Clint said, the rolling radius will vary from one tire manufacturer to another, and from one loading situation to another, and will vary based on how much wear the tire has undergone.
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