Re: Sales Are Way Off, Could It Be the Tires?
Nomen Nescio wrote:
> This new fad of larger wheels and how-low-can-we-go tires just might be
> scaring off the middle-aged bread and butter customers.
> Not too long ago, -75 and -80 tires were the norm. Wheels were mostly 14
> inch for typical family cars and station wagons. Those sizes and profiles
> must have evolved by the application of good engineering sense. They
> delivered fine performance and durability.
> What's driving the recent trend? Today's cars look like they're riding on
> their rims. Could it be this is a cheap and dirty way to lower the cars?
> Intuitively, they look like a hard ride and easily subject to impact damage
> from road hazzards. Also, being as wide as they are, it would seem
> difficult to get them to wear evenly across the tread and equally difficult
> to achieve alignment angles which are always calculated to the center of
> the wheel. Is there a bonafide reason to these new designs, or is it just
> stylists' whim?
> A popular theory is these low and wide tires provide better cornering and
> traction. Is that really the case or just advertising hype? How about
> hydroplaning? If wide tires hydroplane earlier, then there is no merit in
> the traction claim. As for cornering in a passenger car, its hard to beat
> a VW Scirocco and those typically were equipped with -80s.
> Frankly, oversize wheels and undersized tires turn me off esthetically.
> Eyeball engineering tells me they are all wrong. My guess is a sizeable
> minority feels the same and are avoiding the new models solely for that
> Manufacturers need to offer reasonable tire options. Particularly, the 14
> or 15 inch wheel with -80 profiles. Keep in mind there are buyers out
> there who remember 6.70-15 wheels and tires and that roughly corresponds to
> -90 profiles.
A few comments:
(1) Low profile does not automatically (and very seldom does it) mean a
wider tread. Besides, tire manufacturers finally learned that they can
design sipes and wide circumferential grooves in the treads to solve the
hydroplaning issue. For some reason, they were pretty stupid about the
obvious for many years. Nowadays (is that a word?) wider does not mean
inherently susceptible to hydroplaning with half-way intelligent tread
(2) One advantage of larger wheels and lower profile tires is that for a
given tire OD, the brake rotors can be larger - that may be one of the
main drivers to the larger wheels, as attaining problem-free brakes
seems to be a problem on many (most?) cars these days. One of the first
mods I did to my Concorde was to go from 15 to 16" wheels so that I
could convert it to the larger factory rotors - the LH cars really need
(3) One of the biggest downsides of larger wheels is that the rotational
moment of inertia is greater, so straight line acceleration suffers.
(4) Another downside of larger wheels is that tires are priced like
bikinis: As the amount of material in them decreases, the price increase
exponentially (compare prices of 15, 16, 17, 18, 19 inch tires and you
will see what I mean).
(5) As far as the harder ride with lower profile: That can be partially
compensated for with suspension and spring design, although unsprung
weight cannot be compensated for no matter what - and that contributes
to harsher ride.
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