Yes and no. While a lot of riders used Delta during their Tour victories, they seldom used them exclusively. Typically they switched to Cobalto for the mountain stages because of both weight and performance. The common view is that the big Tours are won and lost in the mountains, so it could be argued that the Tours were not won riding Delta brakes.

The thing that amazes about Delta is that they don't work well with many of the Campagnolo rims that were marketed at the same time. Reportedly, Delta performance suffers greatly when the rims are too narrow and many of Camapgnolo's Delta era rims are too narrow for proper performance.