Re: tire width

[Scott Fisher <sfisher71@domain.elided>]

--- MHumphr789@domain.elided wrote:
> Hello everyone!

Hello, Michael!

>     I was wondering how the width of the wheels and 
> thus the tires effects the handling of the car. 

I've run three different widths of tires on three
different rims on two different Alfas.

The widest tires I've run are 195/70-14, on widened
steel wheels (about 6-6.5" wide).  These had decent
grip, but felt slightly numb and made for very heavy
steering.

The narrowest wheels I've run are 14 x 5.5" Turbinas,
currently on my '74 Spider with 185-60 series tires. 
The 185-60 tires are very responsive, with a lively
steering feel and a very light touch in all but
parallel parking manoeuvers, yet they have a pleasing
overall grip.  

Right in the middle are the 185-70 tires on 14 x 6"
alloy wheels, which were hard to judge as the rears
were old, old, old Michelin XZX and the fronts were
not quite so old Michelin Rain Force.  These were
mounted on the '67 GT Junior I used to own.  

Rim width and tire width are related -- the Tire
Rack's Web site, I believe, has a lot of general
information on this (http://www.tirerack.com).  Short
version: you don't want to put a wide tire on a narrow
rim, or a narrow tire on a wide rim.  5.5" rims work
really well with 185-series tires; 6" rims work with
185-195 series tires; 7" rims work well with 195-225
series tires, etc.  

As a VERY general starting point -- wider tires
provide higher grip but also require higher steering
effort, and to some extent reduce steering feel and
responsiveness.  That is, going from the 195-70 tires
to the 185-60 tires made the Spider feel much more
"alive" in steering and in transitional movements --
I'm not yet sure whether this is from the shorter,
therefore stiffer, sidewall or from the narrower,
therefore stiffer, contact patch, but it's clear that
I like stiffer better (no comment :-).

Similarly, lower aspect ratios provide crisper, more
responsive steering feel but also tend to transmit
small-amplitude road surface shocks into the car.

So... decide what you like, and whether you'd like
your GTV to feel different from the way it feels now. 
I think that a 185-70 tire provides a good, neutral
balance of ride comfort and handling precision with
good overall grip, but you can move in a couple of
different directions and change some of those factors,
depending on what blows your kilt up.  I'm a nut for
steering response and sensation, so the 185-60s make
me happy.  If I wanted overall grip and didn't care
about steering effort, I'd find some 15 x 7 rims and
mount the 205-50 (or is it 225-50?) that some of the
competition-oriented guys are using.

One final observation: Alfas are particularly
sensitive to the overall WEIGHT of the tire/wheel unit
-- lighter wheels improve ride AND handling (one of
the benefits to the Turbinas, they're very light).  If
you can find the relative weights of the wheels you
are considering, a lighter one (all other concerns
being equal) will enhance your driving experience more
than a heavier one.

Best,

--Scott Fisher
  Tualatin, Oregon

.
Yahoo! Sports - Coverage of the 2002 Olympic Games
http://sports.yahoo.com

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