Timing acquisition is one of the major challenges in ultra wideband (UWB) communications. Timing with dirty templates (TDT) is a recently proposed algorithm with attractive features such as low-complexity operation, and fast acquisition in the data-aided mode. This paper is devoted to TDT performance analysis. Specifically, upper bounds on the mean square error of the blind and data-aided TDT estimators are derived. It is shown that both estimators are consistent, while data-aided TDT has an edge over its blind counterpart. To ensure good asymptotic behavior, and for the upper bounds to be valid, the shape of the transmitted monocycle should satisfy certain constraints which are specified. Analytical results are corroborated by simulations.