195/55 slowed my car down

[Loren]

Tire pressures are a funny thing and very dependent on the car and tire.

Raising tire pressure can increase the effective "spring rate" of the tire, which is a part of your overall spring rate. Stiffer in the front = more understeer... in theory. The effect is much less on a performance tire with a really stiff sidewall, though. Those tires are stiff no matter what you do. The pleasant side-effect of stiffer tires or more pressure in the front tires is greater steering sharpness.

Raising the tire pressure can cause the tread of the tire to "crown", reducing the size of the contact patch. Again, less contact patch in the front = more understeer... in theory. But, again, a performance tire is likely to have so much radial reinforcement of the tread area that it will stay pretty flat no matter what.

On a FWD car or a heavy car, a more important thing to look at is how much pressure is required to keep the tires from rolling over onto the sidewall. This will over-rule the two items above in most cases.

Ultimately, you want to optimize the contact patch of the tire so that the entire surface of the tread is being used and yielding equal temps across the tire tread. The only way to tune that is with a pyrometer and skidpad testing. But, even then, unless you're willing to make some drastic changes to your suspension, you'll never reach that ideal.

Best thing most people can do is just air the front tires up until they don't roll over past the edge of the tread (there's usually a set of little arrows that mark the max rollover point) in hard cornering. That's going to vary greatly according to what tires and wheels you have, what alignment you have, and how hard you tend to corner.