JoltPhysics: Acceleration problem with sloped suspension

I’m working on bike physics. When I create a bike with a front wheel where the suspension direction is not vertical. and where the rear wheel suspension is vertical, the bike accelerates forwards by itself.

See this video - in it I am not pressing forwards/throttle, the bike is accelerating by itself. I brake half way thru the video and then release the brake. https://www.youtube.com/watch?v=1aKQ4dTFIcw

for front wheel I have:

front_wheel->mDirection = JPH::Vec3(0,-0.5,-1).Normalized();

and for the back wheel

rear_wheel->mDirection = JPH::Vec3(0,0,-1).Normalized();

The bike is kept upright by the old PitchRoll constraint:

vehicle.mMaxPitchRollAngle = JPH::DegreesToRadians(5.0f);

Cheers, Nick