thanks... for some reason LOTS of people don't understand that. ok, time for a math lesson... lets all agree that your geartrain is constant... you axle is going to turn at the same rpm no matter what tire you have hooked up to it, so if your engine turns at say 20000 rpm, the axle turns at 5000 rpm.

ok, got that part down, now lets say we have a 4 inch tire turning at 5000, so it moves 12.56 inches every time around. that times 5000 gives you inches per minute (62800), divided by 12 gives you ft/minute (5233), and finally times 60 and divided by 5280 gives you mph. (59 mph in this example)

now lets say you put those mashers on. same engine, so that still turns at 20000 and your axles still move at 5000 rpm, since you haven't touched gearing. run those numbers above with a 5 inch tire (which is what a masher is), and you get 92 mph.


so, you increased your tire size from 4 inches to 5 inches, and gained a theoritical 30 mph! in practice there are many other variables, the biggest one is your gearing and engine, but in general a bigger tire means faster vehicle and slower acceleration.