QGraphicsView/QGraphicsScene rotating wheel

[carre]

Hi,
i need a rotating wheel and with this code it is nearly possible (without any stucks)

wheelWidget::wheelWidget(QWidget *parent) : QGraphicsView(parent)
{
this->setRenderHints(QPainter::Antialiasing | QPainter::SmoothPixmapTransform);

setViewport(new QOpenGLWidget);

this->setViewportUpdateMode(QGraphicsView::NoViewportUpdate);

wheel_pix = QPixmap(":/wheel.png");

this->setOptimizationFlags(QGraphicsView::DontSavePainterState | QGraphicsView::DontAdjustForAntialiasing);
this->setViewportUpdateMode(QGraphicsView::BoundingRectViewportUpdate);

this->setAttribute(Qt::WA_NoSystemBackground);

QGraphicsScene *scene = new QGraphicsScene(this);
scene->setItemIndexMethod(QGraphicsScene::NoIndex);
setScene(scene);

QLabel *rotateWheel = new QLabel();
rotateWheel->setPixmap(wheel_pix);
rotateWheel->setStyleSheet("background: transparent");

QGraphicsProxyWidget *rotateWheelItem = scene->addWidget(rotateWheel);
rotateWheelItem->setTransformOriginPoint((qreal)rotateWheel->width()/(qreal)2, (qreal)rotateWheel->height()/(qreal)2);

rotateWheel_animation = new QPropertyAnimation(rotateWheelItem, "rotation", this);
rotateWheel_animation->setDuration(14400); 
rotateWheel_animation->setEasingCurve(QEasingCurve::InOutCubic);

connect(this, SIGNAL(start_now_wheel()), rotateWheel_animation, SLOT(start()));
connect(rotateWheel_animation, SIGNAL(finished()), this, SLOT(animation_wheel_finish()));

..

The dimension of this png is 401*401 pixel. The problem is, if i have a additional running progress bar on the main window, the wheel runs with micro lag. What i know it is not possible to put the widgets in different threads. But it seems that the running progress bar interrupt the rotating wheel display (micro - but visible). The OptimizationFlags helps nothing in this case. Have anyone maybe a idea what i can do on such situation?