images and permissions problems

[KWB]

I am using Virtuemart 2.0.24 with Joomla 2.5

I am not able to create thumbnails with my permissions set at 755. Works fine with permission set at 777.

When I change to 755 the folders are not writeable..

httpdocs/images/stories/virtuemart/product/ :: Unwriteable
httpdocs/images/stories/virtuemart/product/resized/ :: Unwriteable

Owner/Groups look to be okay.