what's wrong with the stock tyres I would say there about the best 1/8 truck tyres out there on dirt and pavementAgreed, that makes sense, thanks. But this would at least give a starting point, if the diameter changed. If the simple math suggested 12, maybe you go to 11 or something. But it seems like it at least gives a starting point, vs just kind of guessing and picking a number of pinion teeth arbitrarily.
I just got belted street tires for my truck. They're basically the same diameter (tiny bit smaller), but heavier. However, being belted, they also don't balloon. I'm hoping that, at least at speed, this may help kind of offset some of the added weight. It will reduce the actual top speed/effective-gearing, vs the ballooned-out stock tires. I guess I'll need to keep an eye on temperatures.