Re: Tire width

[Simon Favre <simon@domain.elided>]

Even if they fit, you may find another problem. If the car wallows
around as much as you say, wider tires may actually be WORSE! If you
read the book "How to Make Your Car Handle" by Fred Puhn, he talks
about a major consideration for suspension modifications. The one
I'm talking about is camber change due to body roll. As the car leans
more and more to one side, the camber of the outside front wheel gets
more and more positive, which makes the tire tread roll up under the
car. There are some classic photos in Puhn's book illustrating this.
With a wider tire, the car can become more sensitive to roll-induced
camber change. This is less of a problem in the rear of a Spider due
to the live rear axle. Dialing in some negative camber in front helps,
but if the suspension is way too soft, you will probably not like the 
result. Too much negative camber will cause the tires to wear unevenly
if you also drive it around. I tend to think 205 is as wide as you
should go. There is another issue with width. If the tire is at the
wide end of the allowable range for the rim width, the tire will tend
to squirm side to side on the rim. There's a reason tires are listed
with a "design width" for the rim. That's the rim width the tire works
best on.

Glenn Wasserman wrote:

>I have a '93 Spider Veloce and I'm looking for autocross tires. I've 
>found a used set of Toyos that are 225/50 15" size. These will fit my 
>wheels, but can anyone tell me if they will clear the body work?
>
>The springs/shocks are too soft, and I find that the car leans, 
>squats, and dives a LOT under heavy driving (i.e. autocross).

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