Partitioning External Drive w/o Erasing Data

Question

I have one 500GB external drive (USB) that I want to partition. I have 85GB on data on it now and really don't want to copy it back to the Mac HD (if at all possible).
When I run Disk Utility/Partition and select 2 partitions, it allows me to shrink either partition to ~52GB - smaller than my current data size. So I'm not confident what I am doing will partition w/o erasing data.
The drive is formatted as Mac OS Extended (Journaled).
My eventual goal is to use SuperDuper for a clone backup. I'm using the free version that only allows erase & copy. If I purchase SD, could I add a clone to the external w/o erasing existing data?
Any other suggestions?

Answer 1

yes you can.
quote from disk utility help:
Creating new volumes on a disk
You may be able to create multiple volumes on your disk without losing any data. Each volume works like a separate disk. You may need to create a new volume if you want to install multiple operating systems on your computer. Volumes can also help you organize your files.
NOTICE: Back up your data before creating new volumes on your disk as a precaution.
To create new volumes on a disk:
Select the disk from the list at the left, and click Partition.
Select an existing volume in the Volume Scheme list, and click Add .
Disk Utility splits the volume into two, leaving the data in one of the new volumes. If the volume is less than half-full, Disk Utility creates two volumes of equal size. Otherwise. it creates one volume large enough for the data, and another volume with the remaining space.
Resize the volumes as needed.
You can drag the dividers between the volumes in the Volume Scheme list, or you can select a volume in the Volume Scheme list, and then enter a value in the Size field.
Choose how to format the volumes that will be erased or created.
For each new volume, select it, enter a name, and then choose a format.
Click Apply.