The tire and wheel setup I'm considering now for 12's

[John_D.]

Here's the full setup I'm now looking at:

Bogart D10's (or Fluted Stars)
15 x 9.75 est. 10 lbs each
15 x 4 est. 9 lbs each

BFG DR's
275/50 15 (25.8 x 10.83) est. 22 lbs each

MT ET Fronts
26 x 4 15 (25.9 x 4.9) est 12 lbs each


So, the front tire/wheel combo would be 21 lbs each side, or 42 total. Compared to my Miglia's that are 55 each side, or 110 total. That's a ROTATING weight savings of 68 lbs, just on the fronts!!

Rotating weight is supposed to cost .1 et for every 10 lbs.

Now, take my 13.2 I got with those 18's on the front, and a buddy's ET Streets on the back. Subtract .7, just for the front wheel weight reduction.

That's potentially a 12.5 with no other mods to the car. :D

This is assuming that the bfg dr's I'm planning to put on the back are only two lbs heavier each, than the same size ET Streets that I ran the 13.2 on. I don't have the definite bfg weight #'s yet though... So I might be a little off there. But, the bfg's should trap a little higher.

[Slow-N-ugly]

Well that would be true only....

Its 100lbs=.10

If it was 10lbs=.10

James would be in the 9s'

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Slow-N-ugly:
Well that would be true only....

Its 100lbs=.10

If it was 10lbs=.10

James would be in the 9s'<hr></blockquote>


'rotating' weight is totally different...

[Slow-N-ugly]

So where did you hear that figure at?

[John_D.]

<blockquote>quote:</font><hr>Originally posted by Slow-N-ugly:
So where did you hear that figure at?<hr></blockquote>

A year ago I ran across it all over the place. Now I'm having a hard time finding any references...

Here are a few:
Point:
------
Bottom of page two of this article:
http://www-unix.oit.umass.edu/~tcroy...ineinertia.htm

The start of the torque converter section of this article:
www.nissaninfiniticlub.com/artman/publish/article_1.shtml


Counter point
-------------
http://www-unix.oit.umass.edu/~tcroy...ineinertia.htm


Basically, after reviewing these more closely, there are three rotational speeds that matter.

Crank speed (the fastest), tailshaft/driveshaft speed (the middle), and wheel speed (the slowest).

The mass on the fastest rotation has the most effect, and the mass on the slowest rotation has the least effect. So wheel mass would count less than driveshaft mass.

However, mass at the outer edges (like the outer edge of the wheel vs. the hub) makes more difference than the mass closer to the axis.

In any case, I think the 10 lbs rotating = 100 lbs static, is oversimplified, and probably overstated for wheels and tires.

I'll just have to test before and after et's on the same date... And see what I get. Although traction will come into play too... So who knows...

[Wicked 3800 V6]

Believe it or not, GRM just had a part of an article dedicated to how little a DS helps in terms of rotational, b/c everything is close to the center. Either way, DS is a loss of weight, and for us it's a steup up from a lossy 2-piece.
-Rob