Okay, I'll bite. Whatever tire your run, divide the section width by
25.4 (millimeters per inch) and you will get how wide the tire is in
inches. Then multiply by 70% (.70) and round up to the nearest half
inch. This should be considered the minimum rim width.
All things being equal (and they never are) the closer the rim width is
to the tire width, the more precise the handling. Conversely, the ride
improves (comfort) as the rim width gets smaller than the tire width.
Example: 195/60R14 tires.
195 / 25.4 = 7.68 inches wide 'section width'.
Minumum rim width (* .70) is 5.37 inches -- round up to 5 1/2.
Optimum rim width is 7.5 inches.
Example: 6 inch wide rims.
6 * 25.4 = 152.4 thus *minimum* tire width would be 155s.
152.4 / 0.70 = 217.7 thus *maximum* tire width would be 215s.
The second value 50, 60, 70, etc, is how high the sidewall is as a
percentage of section width. It shouldn't have anything to do with the
width of the tire -- just it's height.
Example: 195/60R14 tires.
>From above, they are 7.68 inches wide.
The side wall height would be 60% of 7.68 inches: 4.6 inches.
Tire height would be 4.6 + 4.6 + 14 = 23.21 inches. (Or the width of the
top and bottom of the tire plus the wheel diameter.
Having rim widths wider than your tire width causes you to start eyeing
big, old GM sedans and pondering what 5,000 audio watts and hydraulics
would contribute to your procreation chances.
Robert Allen, Kansas City
'69CGT w 195/60R15 tires (7.67 inches wide, 24.21 inches high)
'75TR6 w 215/65R15 tires (8.46 inches wide, 26.00 inches high)
'95Z28 w 245/50R16 tires (9.65 inches wide, 25.65 inches high)
'96TWK w 225/70R15 tires (8.85 inches wide, 27.40 inches high)
'86 Boat w H78/14 trailer tires (I have no idea!)
EMILY COWEN wrote:
>
> Hi Robert Allen!!
>
> On Fri, 23 May 1997, Robert Allen wrote:
>
> > So you take a tire several sizes wider than stock and put the 'book'
> > pressures in it and the ride is squishy. (sp Todd?) Then you pump it up
>
> But NOBODY has adressed the rim width issue. The WIDER the rim width
> WITHIN the manufacturer's recommended range, the more stable the tyre
> contact patch, and the quicker the tyre response to steering input.
>
> TTUL8r, Kirk Cowen (who's always amazed at how his motorcycle corners)
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