so I am running 35's now and am thinking of 37's. I've already sleeved and gusseted the dana30 about as best I can do with stuff from EVO.

So here is the question, I look at my current combination of Mickey Thompson MTZ's (68lbs/each) on steel wheels (38lbs/each) and the total weight is 106lbs. If I get a 37" that is the same weight and then get aluminum wheels to wrap them around and net out a reduction in weight . . . am I actually doing better for my axles then sticking with heavier and smaller tire/wheel combination?

 

No because it takes more torque to turn a bigger tire, which in turn puts more stress on driveline components and the axles

 

bummer, i was thinking it was a combination of both the weight and the size and by lowering the weight it would offset the added stress of the extra size. Guess I shouldda taken a physics class in college.

 

I'm no physics major either. Size, weight, rolling mass all have a bearing on performance. But you also need to know that for every take, there is a give. Lighter tires are probably less durable ( C rated ). Heavier tires add to the mass of the vehicle ( E rated ).

 

unsprung weight.

 

That's what I'm trying to figure out, how much give and take for each choice and how close does it come to a wash. I could go from my 35" MTZ's and go to 37" BFG MT KM2's that are only 2.86lbs heavier per tire. I can more than offset that by getting allow wheels that will weigh in 18lbs less per wheel! It would seem to me that a net reduction of over 15lbs per wheel/tire combo would be pretty significant, but is it big enough to offset an additional 1" of height on either side of the axle (top & bottom) ??

I have no idea.

 

Like I said. "No Expert Here". But you probably should make thes choices based on how you plan to use the vehicle. I would say that lighter is always better. But aluminum rims and C rated tires will probably not hold up very well on the trail.

 

Less weight does play into it though....weight=resistance

 

As far as breakage I would say the taller tire would be worse.

If you double the weight of the tire you only double the stored energy. If you increase the the distance from the wheel center the stored energy goes up by the square of the radius change. So a tire that is twice as tall would have 4 times the energy.

When the tire looses traction and then suddenly grabs you are more likely to break a shaft with with the taller tire. If the taller tire gets bound up it has more leverage to twist and break a shaft also.

 

This one sounds like a vacation from hell.