[V8] tire size

[Coleman, David]

> -----Original Message-----
> Guys, A larger rim doesn't have to mean more rotating mass or 
> larger diameter wheel.  The trick to going with larger rims, 
> is to keep the overall diameter of the wheel as close to 
> stock as possible....

But of course... I/we was referring to the tire's ratio (55% of 225) as
being too tall, which made the overall (wheel/tire combo) diameter too
big by about 7 mm -- not the wheel's 1" increase in diameter itself.
Andrew's MPG and performance issues likely stem from both an overall
diameter increase (adversely affecting final drive) and the tire's
taller sidewall itself (adversely affecting the stability).   This is
all in comparison to, as you state, the OE's overall 15" wheel/tire 25"
diameter...

Regarding rotating mass, however, just about any larger wheel will
result in an increase here.  First, you're moving a good bit of rotating
mass further away from the axle (increasing angular momentum and more
inertia to overcome).  Second, larger wheels typically weigh more than
smaller ones, as does the required larger tire.  After correcting the
sidewall ratio for the larger wheel, a 16" tire will still weigh more
than the same tire in 15".

Something else to consider is that your braking capability hasn't really
been affected due to the stickier rubber and increased contact patch of
your current setup.  Better gription offsetting more rotating mass...

PS:  It was great meeting you this past weekend.  I didn't notice your
wheels were 18", which is too bad since I'm likely headed in that
direction myself, and woulda taken a closer look.   I have couple pics
of our two cars side by side; I'll have to download asap!

-davec.




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