Pete-<< What is it for, and should it be used with TA 9-speed and 9/10-speed chainrings used with a 9-speed setup? >><BR><BR>
It is because the other arms of the 10s big ring have a little material taken off of them to make the 10s ring a wee bit closer to the small ring. If the arms of the TA ring do no have material removed(they do not) no need for the thin washer.
Peter Chisholm Vecchio's Bicicletteria 1833 Pearl St. Boulder, CO, 80302 (303)440-3535 http://www.vecchios.com "Ruote convenzionali costruite eccezionalmente bene"