On Fri, 21 May 2004 23:45:54 -0400, Andrew Perlow wrote:

> Any opinions on 90 Spirit tire size change from 185/70R14 to 195/60R15?
> Is it worth the cost of new wheels?

I'm with Dan. It's probably not worth it.

At best, I would expect maybe a slight drop in fuel use at highway speed
*IF* the overall diameter of the tire rubber is larger. But if my math
is correct, they're not.

IIRC, the first number is tire width in millimeters, the second the
percentage of that number that the sidewall measures, and the third
being the rim diameter in inches (or the diameter of the inside hole of
the tire, effectively the same thing).

185 * .70 ~ 130mm. 130 / 25.4 ~ 5.1 inch sidewall. times 2 (one for each
side - make a diameter instead of radius), is 10.2, plus 14 for the rim
diameter is 24.2 inches overall diameter.

195 * .60 = 117mm. 117 / 25.4 ~ 4.6 inch sidewall. Times 2, 9.2. Add
15, is 24.2 inches overall diameter.

Hmmm. Seems to me you would have no gain whatsoever beyond simple
cosmetics. You tell us. Is it worth it?

FWIW, I have 205/60R15s I think. That makes them 24.7 inch overall
diameter, so there's not much difference there, either.

OTOH, you have to consider handling as well. You will have a different
contact patch which may be larger or smaller depending on the weight your
vehicle places on them. If you have a lighter vehicle, you'll want
narrower tires. Heavier, wider. Otherwise, you wind up with a car
that's so light it doesn't flatten the tire to the road for a proper
patch, or so heavy it wears out the tires too quickly. In addition, the
sidewall affects cornering ability, as it's a flexible piece of the
suspension. I might consider changing all that for racing, but not for
street driving. Even doing 70 mph up a 35 mph 270-degree circular onramp
to an interstate highway like I sometimes do won't bring you anything
that you'll notice much change in. Shouldn't be going that fast anyway,
I know.

Overall, if you don't race your car professionally or at least in some
form of amateur circuit, don't spend money on rims. If you're going
purely for cosmetics, consider the junkyards. Seriously. I purchased
two rims from two yards. Both snowflake. Each rim got a fresh tire and
replaced the donut spares in my car and my friend's car. One cost $20,
the other $7 (yards vary, shop around). So now, for $27 and the cost of
2 new cheapo tires, I wound up with 2 perfectly good full size spares.
205/60R15. Assuming $20 for each rim and $40 (guessing) for each tire,
you're looking at $240 to replace all four, $300 if you include a spare.
You'll be lucky to get new rims alone for that price around my area.
YMMV.

Hope this has helped somehow. I know it's rather long (my trademark) but
hopefully it answers your previous questions and helps answer future
ones.

Good luck

CJ