Am i getting screwed by the dealer?

[quote=“newman,post:16,topic:39904"”]

Here is WHY it is true.

Given:
235/84/16

tire diameter (Tn) = 31.7

Assume: 9/32 tread depth

At 50% wear, tire diameter (Tw) = 31.7 X 2(9/64) = 31.42

Assuming you are traveling at 70mph:

w = th/t

s=r*th
then
th= s/r

so

w = s/ (r * t)

but since v = x/t

or in this case

v=s/t

w= v/r

so

w = v/r

since r=d/2

w = 2v/d (radians)

1 rad = 180/pi degrees

so

w= 360v/(pi*d)

Angular slip (As) will be defined as wn-wu

SO

at 70mph = 73 920 in/min

As = 360*v/pi (1/dn-1/du)

As = -2381 degrees per minute.

since 1 ROT = 360 degrees

As = -6.61 rpm

So, for every minute you drive, your differential is SLIPPING 6.6 times every minute. I’m sure you can see how this would be BAD for any differential.

EDIT: I LOVE MATH.

[/quote]

Does weight ever come into play or is it strictly overall rolling diameter (being equal)?