NEVER.

Not even during the Noah's Ark years of 1897 thru the 1910's. Not even during the nightmare-inducing Cooper years. Ohio State under Tressel and Urban has gone on the best run of dominance either team has had in the entire history of this rivalry. 

For reference: TTUN's best run of 17 was in those biblical times aformentioned. Back when UM playing tOSU in football was like an NFL team playing a minor league team, due to the former having started football and achieved status as a major program much earlier. 1897-1920: Michigan led with 13 wins, 2 losses, 2 ties. Fledgling Ohio State managed to eek out two ties, and end that era with two wins, thanks in large part to Chic Harley.

Ohio State's previous best run of 17 was during the Woody Hayes years. 1952-1968: Ohio State led with 12 wins, 5 losses.

Hopefully you all appreciate this dominance like never before, and here's to Ohio State taking the all-time series lead within the next 9-11 years. GO BUCKS.