**nsxtasy, I'm not getting quite the same numbers.**
Sure, let's take a look.

**I always use the manufacturer's revolutions per mile as a starting point figuring it's the highest resolution value available, although diameter is probably close enough.**
Either one should work, except for rounding differences.

BTW, I took my numbers from the

Powerdog tire calculator website. They do a straight calculation based on wheel size and tire size. Those measurements SHOULD be the same as the Bridgestone specs on the Tire Rack website (but they aren't; more on that in a moment).

**Here are some of the numbers: (Larger value = smaller diameter)**

Pre '94

Front: 896
I'm not sure where you get that number. When I look at the Tire Rack's specs for the Bridgestone S-03 in 205/50-15, it says 902 revolutions.

**Rear: 807**
I'm not sure where you get that one, either. Tire Rack says 837 for 225/50-16.

**'94 on**

Front: 879
I'm not sure where that one comes from. I can't even find the 215/45-16 size on the Tire Rack website for that tire.

**Rear: 840**
THAT one I see.

**nsx-808 tires on average rim widths:**

___________Early Late

Front: 833 +7.56% +5.5%

Rear: 814 -0.9% +3.2%
833 and 814 are the same revolutions stats I see on the Tire Rack website.

Recalculating using the revolutions numbers that I found on the Tire Rack website for the stock tire sizes, it looks to me like the changes would be:

___________Early Late

Front: 833 +8.3% N/A

Rear: 814 +2.8% +3.2%

Those numbers are pretty close to what the powerdog calculator had provided, per my previous post:

___________Early Late

Front: 833 +8.7% +6.2%

Rear: 814 +2.6% +3.2%

So unless I'm mistaken, I think most of the difference may have occurred because you might have pulled the wrong numbers off the Tire Rack website.

-------------------------

What's interesting to me, though, is how Bridgestone calculates its numbers, and how the revolutions per mile differ from the powerdog site. Let's take the 225/50ZR16 size as an example. Bridgestone and Powerdog both calculate the outer diameter of this tire as 24.9 inches. I'm sure Powerdog calculates revolutions per mile by simply multiplying this number by pi (3.1415926536) to get the outer circumference, and then dividing that result into 63360 (number of inches in a mile). If you do that, 63360 / (24.9 x 3.1415926536) = 810 revolutions. Powerdog shows the revolutions as 811 (the difference due to rounding, since it was probably not EXACTLY 24.9 inches in their calculations). However, the Bridgestone website shows this figure as 837 revolutions per mile - a substantial difference. I am guessing that Bridgestone somehow calculates a figure for "rolling" circumference rather than the calculated outer circumference, to take into account the amount of deflection caused at the contact patch. Clever, and undoubtedly more accurate. However, as we can see, it has little effect on the percentage differences, since this adjustment is performed on the before AND after measurements.

**Darn, I had work to do tonight!**
Yeah, me too. But this seemed like one of those "Stump Ken" puzzle distractions...