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Originally Posted by Twinbo
Any issues with steering weight/feel by moving to a wider front tire? Is turn in affected? I can't say that I have the ability to sense these small changes but I am interested none the less.
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There might be. It will depend on a lot of things, like offset, tire size, diameter, tire compound, camber angle, and, of course, something called slip angle.
On most cars, the axis about which the front wheel turns isn't vertical, nor does it intersect the tire through the center of it's contact patch. The wheel will tend to roll around the rotation axis when the wheel is turned. The radius between this axis and the wheel center is called the scrub radius. The specific wheel you pick can affect the length of this radius and therefore, the torque needed to turn the wheel, at speed. A similar effect occurs in because of something called caster. The wheel will tend to lean left or right/scrub across the pavement. This is what causes the car to move slightly when you turn full lock to full lock. Its the reason wheels tend to look as though they are leaning out when the car is turning. It also has a huge effect on steering effort and by extention, feel/turn in, because the vehicle will tend to heave a bit (You are fighting the vehicles weight, as well as the firction between the tire and the road). For that reason, you will find that heavier vehicles tend to have less caster and camber than smaller, more sporty vehicles. But, having less of both tends to make the vehicle less stable at speed, up to a point.
Know that this mechanism is the only mechanism the driver has to receive feedback through the steering system. The amount of restoring force that is working to return the car to 0 degrees of steer tells the driver a huge amount about how much traction he has left.
So yeah, different tires can have a huge effect upon feel and turn-in, technically speaking, anyway. Whether or not a driver cna feel those effects is another matter. (although, i'd say that many drivers can feel a difference but, might not be able to understand what is changing and how to take advantage of it).
About the slip angle bit, this angle increases to a max value, at which point, the tire losses traction and you eat shit. That max value varies per tire. But, suffice to say that each tire behaves very differently as it approaches this limit. Some are linear, some are progressive, some are regressive. You have to know how your tires behave at this limit because, you don't want surprises.
God, I miss chassis design.