No expert here, but I would say train fast to ride fast. It sounds like you are getting enough miles but need some speed work. Maybe dedicate 1 ride per week to speed training. Could be intervals or riding with a faster group, or just pushing yourself. I think even 30 mins at a couple mph faster than your normal pace would pay dividends. Not immediately, but over time. I've used that to get from about 15 to 16.5 mph ave, only doing around 80 miles a week total.
scott s.
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