Adam, SanDisk use HDBench to derive their performance numbers. This program tests a card like a hard drive. It is freeware. An English version for the download can be hard to find. I have a link to one such site
here. (Scroll down until you see the HDBench link in the left column. Click it, then locate "HDBENCH Ver3.40 beta6" on the next page. That section has the download link.) The file size is around 250kB, the file name hdb340b6.lzh. Yes, it is packed with LHARC. I do not know if WinZip can handle this. PowerDesk Pro 6 does. There is also a lha.exe for Cygwin.
TugZip handles LZH and other formats, has a GUI and is free. It looks like a nice free WinZip replacement.
So, if you can be bothered, download the hdb340b6.lzh file and unpack it into a new directory of your choice. That completes the installation. Launch hdbench.exe to see a window similar to the one shown by the first link. The disk/card test is in the bottom row. Choose the card reader partition in the first combo box. Then choose a test size in the other combo box. Click on the bottom left icon to start the test. I usually run the test with sizes of 1MB, 2, 4, 8, 10, 50, 100MB to see how a card handles different file sizes. The results are "Read", "Write", "RandomRead", "RandomWrite", in kB/s.