Originally Posted by
HillRider
That's it exactly. FC-6500 was the first of the 9-speed groups and older 6/7/8-speed chainrings were indeed spaced a bit further apart and a 9-speed chain could slip between them. Any 9 or 10-speed chainring (FC-6600, FC-6700 or their 105 and Dura Ace equivalents) will work fine.
The FC-x700 series was the beginning of the spider with the integrated hollow spindle and had a different chainring attachment. No bolt hole on the outside of the spider, and different attachment of the smallest ring. Need to check the BCD/PCD of the 3 rings. The 9 speed cranks used 130/74 BCD.