Detroit IndyCar: Helio Castroneves ends Friday practice on top

Castroneves set a 1m15.1511s, two tenths faster than Rahal's best effort.

Many teams avoided doing significant running in the afternoon because the tyre allocation is the same as for a normal street course weekend even though Detroit features two races.

That encouraged tyre preservation ahead of Saturday morning's first qualifying session.

Alexander Rossi was third fastest, despite crashing out.

The Andretti Autosport driver had just placed his Dallara-Honda top of the timing sheets 10 minutes into the session when he lost control coming into the Turn 9 left-hander in the Fountain section, significantly damaging the rear of his machine.

Reigning champion Simon Pagenaud was fourth fastest, ahead of Mikhail Aleshin and Indianapolis 500 winner Takuma Sato.

Seventh-placed JR Hildebrand completed more laps than anybody else with 19.

Ryan Hunter-Reay spun part-way through the 45-minute session, and was ninth fastest. A suspected clutch issue also hampered his session.

Max Chilton suffered a brake fire in the pitlane, and ended the session in 15th place.

Ex-Formula 1 driver Esteban Gutierrez ended his first day as an IndyCar Series driver slowest of all, over three seconds off the pace.

SECOND PRACTICE TIMES: