Underworld Gamepad problems

I've got the PC version of Underworld and have just arrived in
the Mexico segment. So far, so good, except the motorbike
completely ignores the gamepad. I'm using a four-axis, 16 button
PS2 pad via a USB convertor.

It's weird in as much as the rest of the game (including Lara
herself) totally works as expected with the pad. Get on the
bike and the front wheel will turn left and right with the left
hand joystick on the pad, but pushing up or down doesn't
move the bike backwards and forwards as it should.

The keyboard 'W' and 'D' still do it as they should, but not
the pad. As there's nothing to change in the options settings
I'm guessing this is something hard programmed so that the
game can tell how much I've moved the joystick to decide
how fast to accelerate. This works perfectly for Lara in that
she slinks, walks, jogs and runs all depending on how hard
the joystick is tilted. With the bike - nada, zip, nothing.

Anyone any ideas about how to get the motorbike to work
with the gamepad?

Cheers

Regards

Mark