Ribble Road Bike 50cm 531 Frame - Tiagra 2 x 10 speed ST4600 gearing - Vintage | eBay
Shinano Tiagra ST4600 2 x 10 speed gears, I've only ever really used the lower gear ratio which all change really quietly and run smoothly. It does change to the higher gear ratio and a quick test says it runs well but not used them a lot so can't say for sure as I've not been going 25mph on her.
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