Still have that trani lag.

[Jackpine]

Your point is well taken, and I'm possibly wasting everyone's time - you could even be writing tunes! (But, you need a break from work now and then).

Good observation about the spin up time using a balancing machine. That DOES clearly show the effect of getting the greater mass into motion. I grant that there IS that effect, but as a percentage of the total power delivered by the truck's engine, I think the tire mass effect is greatly overshadowed by the loss in mechanical advantage due to the greater distance between the axle and the road. And, that was what I thought I was saying.

Doesn't an aggressive, wider tread contribute more to "rolling resistance" than anything else? That's certainly the effect I feel between a mountain bike and a road bike when pedaling or coasting.

There clearly IS some optimum gear ratio and tire size combination for each of the following though:

1. Acceleration (0 - 60)
2. 1/4 mile speed
3. Fuel economy at cruise
4. Max top end speed (accelerator floored)

And, unless I'm totally out to lunch here, I think each one of these goals requires a somewhat different combination.

I suppose I'm reacting to the "one size fits all" mentality I've observed by some posters in other forums where they seem to think they can mod their trucks in such a way as to get all four of the goals I cited above at once. I'm especially amused when they complain about economy after putting in mods to improve acceleration.

- Jack