Dumb question

[Brion Toss]

Hello,
It is true that when the loads are highest (on the wind, in a breeze) the load is primarily vertical, and that can make it hard for some cars to slide to leeward. And on some boats, like maybe Ian's, positioning the car isn't critical. For instance on a gaffer, you pretty much want to have the car on one side or the other, to minimize leach twist.
But on most contemporary boats, that traveler is a precision instrument, and you should be able to put it where you want it, when you want to; it can have that much of an effect on sail trim and helm balance. So if yours won't go to leeward on its own, something is very wrong. Remember, even on the wind, at least 20% of the sheet load is expressed laterally, so if the bearings are remotely efficient the car should move easily to leeward. And given enough purchase it should also be easy to take uphill as needed.
If this isn't happening, you can hope that the bearings simply need cleaning and lubricating. On a Harken car, or any other with exposed Torlon bearings, that means a little soap and water, then some "One Drop" oil from Harken on the bearing races. But it is also possible that you simply have a crappy traveler. If that's the case, get a good one. The difference will be profound.
Fair leads,
Brion Toss