DTM tyre supplier Hankook has revised its procedures after finding what it described as a variance in "weight median" following a post-Lausitzring analysis of its tyres.
A scheduled two-day test after the second event of the season was cancelled amid questions raised by BMW and Mercedes about tyre performance during a weekend dominated by Audi.
The DTM requested a "detailed analysis and a prompt clarification" from Hankook, following feedback from a number of teams that the control tyre was "deviating in its handling characteristics from empirical values".
The review confirmed that all of the tyres were within Hankook's design guidelines, but that the latest batch of its rubber had a higher weight median and was closer to the permitted upper limit.
Tyres are allocated via a raffle at each event and with the previous batch having been closer to the lower limit, Hankook says this weight difference - albeit both within the DTM's defined range - could have accounted for the performance anomalies.
A new "downstream control unit" has been added to the tyre production process to eliminate the variations, and tyres to be used this weekend at the Norisring have been inspected and cleared.
All three manufacturers returned to the Lausitzring last week for the postponed test.
Undefeated so far in 2015, Audi reported that it completed approximately 1100 miles across two days.
Past champions Mattias Ekstrom and Mike Rockenfeller were joined by Formula 3 European Championship frontrunner Antonio Giovinazzi, sampling DTM machinery for the second time after testing for Audi last December.