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Thread: Matching Tires and Wheels: Handling vs. Ride Comfort as a Function of Wheel Width

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    Village Idiot goldstar's Avatar
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    Matching Tires and Wheels: Handling vs. Ride Comfort as a Function of Wheel Width

    The question often arises as to the maximum width tire that can be mounted on a wheel of a given width. Most of you are aware that there is a recommended range of wheel widths on which a given-sized tire can be mounted. Since tires have flexible sidewalls, a single tire size can be mounted on a variety of wheel widths, within reason. Basically, both the width of the tire and its aspect ratio determine its appropriate wheel width range. A tire/wheel width chart can be found at:
    http://www.yokohamatire.com/customer...ing_width.aspx
    This leads to two questions: Why should the the recommended wheel width range be followed and what effect does wheel width have on a tire's road characteristics?

    In the US, the Tire and Rim Association (TRA), http://www.us-tra.org/traHome.html composed of representatives from all the major and most of the minor tire companies, has developed technical specifications in this area based on engineering principles and empirical testing. These studies have demonstrated that wheel widths outside these ranges, either over or under, will stress the tire in a manner that may result in poor service and potential tire failure. The Euro Tire and Rim Technical Organization (ETRTO), www.etrto.org serves a similar research function as does the Japan Automobile Tire Manufacturers Association (JATMA), www.jatma.or.jp/index.html

    Most of the following material is taken from these two sites:
    http://yokohamatire.com/customer_ser...stomizing.aspx
    www.tirerack.com/tires/tiretech/tirespecskey.jsp
    The wheel width recommendations are completely independent of the tire or wheel manufacturer. A tire actually has three width measurements: nominal size (the size molded on the tire), section width (distance from sidewall to sidewall-the widest part of the tire), and tread width (see illustration at bottom of page). Furthermore, two different brands of the same nominal width tire can have different section and tread widths. For example, in the case of a 195/55-15 tire, the Yokohama AVS ES 100 has a section width of 7.8" and a tread width of 7.1", whereas the Bridgestone Potenza RE92 has a section width of 7.7" and a tread width of 6.9". In both cases, however, the wheel width range is specified as 5.5"-7.0". A given wheel range can be further subdivided into wide, midrange and narrow. In the above example, a 5.5" width would be considered narrow, 6 or 6.5" would be mid and 7" would be wide. According to Yokohama, adopting a wider wheel increases vehicle stability and improves steering response and cornering ability. Choosing a narrow wheel results in an improvement in ride quality but sacrifices the tire's ultimate performance capabilities. On the other hand, a midrange wheel provides a balance between handling and ride quality.

    Note that the width of the wheel will influence the width of the tire. A tire mounted on a narrow rim is "narrower" than the same tire mounted on a wide rim. Since wheels are made in increments of .5" widths, the industry rule of thumb is that for every .5" change in wheel width there will be a corresponding .2" change in section width of the tire. In connection with this, the TRA has established a measuring rim width that enables all tire manufacturers to measure their tires on the same width wheel for comparison purposes. For aspect ratios of 50 or higher, the measuring rim width is 70% of the tire's section width rounded off to the nearest .5". For aspect ratios lower than 50, the measuring rim width is 85% of the tire's section width. Returning to the above example of the 195/55-15 yoko tire, the 7.8" section width was obtained from a measuring rim width of 6". The same tire mounted on a wheel with a 6.5" width would have a section width of 8" and if mounted on a 7" wide wheel would have a section width of 8.2".

    Yokohama, as well as other industry sources, goes on to say that a good rule of thumb is to use a wheel width 90% as wide as the tread width (not the section width) of a performance tire for street applications, to provide a good balance between performance and ride quality. Let's see how this would work out for a couple of popular upgrade sizes again using the Yoko AVS ES 100 tire:

    205/45-16, width range = 6.5"-7.5", tread width = 7.9", 90% tread width = 7.11", correct wheel width size = 7"

    215/40-17, width range = 7.0"-8.5", tread width = 8.4", 90% tread width = 7.56", correct wheel width size = 7.5"

    Happy Motoring!
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    Going broke in style.
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    I didn't realize that the wheel width affected the ride comfort... I knew the sidewall did. Great to know, thanks for the info!

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    Quote Originally Posted by goldstar
    Obviously, where the highest performance is desired and ride comfort is not a factor, use the 7.5" and 8.5" wheel widths, respectively.
    Well, that's right to a certain extent. Wider wheels weigh more and therefore provide greater unsprung weight and greater rotational inertia. The weight savings with a narrower wheel may have a performance advantage.

    It is well known that a small diameter wheel has better performance than a large diameter wheel. Ultra low profile tires are also not the fast setup. (Look at a Formula 1 tire.)

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    THE CREATOR escortkid's Avatar
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    too a point but running 13 inch tires on our cars is not fast. 15 16's are the best size handling wise 17's are good too.
    mods: engine: fm stroker lightened and knifedged crank, 11:1, custom crank scraper, fully p&p head and intake mani, bored throttle body, flowed and matched stock injectors, rx7 vaf, apexi safc, gude race cams, modded ecu 8200 fuel cutoff, blaster coil, clutchmasters stage 3 clutch, fidanza fly wheel and timeing gears, msp diff, custom shortram in a cold air box

    suspension: s/r struts intrack springs and intrax sway bars 15x6.5 rims kumho mx tires 205 50 r 15

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