TGraph: more space for y-axis label

Hi all,
a very short question for you, I think:
Look at the enclosed picture. They are four TGraph objects.
As you can see y-axis labels are not visible, at all.

In the top-left pad I tried to set a 0.1 offset, but now they are overwritten by the graph itself.

Can you suggest me a way to improve it?
Can I enlarge the label space on the left of each pad? Can I force the labels to be written over the graph?

many thanks!

gPad->SetLeftMargin(0.15); //15 per cent of pad for left margin, default is 10%