Upgrade or new bike time?

I'm riding more and more, and getting faster and faster. My average speed on a 30-50 mile ride went from 18 last year to low 20's this year.

I'm on a 2011 Tarmac Elite, ultegra group, H+Sons wheels with white industries out back and dtswiss 350 up front, Sapim CX Ray spokes all around.

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