Good morning everyone.

I'm a noob/retread trying to upgrade my bike and I have some compatibility questions that I hope some of you can help me with.

First, are Shimano Ultegra BR-6600 or BR-6500 calipers compatible with RSX 7-speed brake levers/shifters? (Shimano says the new BR-7700 only work with the 7700 levers but I don't know if that was true of the older models)

Next, where can I find the "reach" specs for BR-6600 calipers? It looks like I need ~47mm

The bike is a 1983 Trek 620 steel-framed road bike, which I upgraded to Ultegra 7-sp SIS drivetrain many years ago. I'm in the process of upgrading the Downtube shifters to RSX brake lever/shifters, and thought I might upgrade the calipers at the same time.

Any thoughts would be very much appreciated!

-Tom in SoCal