The Spanish Grand Prix at the Circuit de Catalunya heralds the first pivotal point in the season, the return to Europe seen by the teams as the first opportunity to roll out larger upgrade packages. Let's take the opportunity to look through some of the upgrades applied by the teams.

Red Bull

A critical area this season is the area around the rear tyres. The change of construction by Pirelli to its 2013 tyres means the sidewalls deform under load which in turn impacts on the aerodynamics. 'Tyre squirt' is when airflow is deflected off the rotating wheel/tyre and pushed laterally into the diffuser's path. This is why the teams are so eager to target the exhaust plume in the gap between the tyre and the floor as it blocks the effects of 'tyre squirt'. The problem comes with the transition between on and off throttle, as the driver lifts out of the throttle and the exhaust plume dissipates once again 'tyre squirt' begins to play its role destabilizing the diffuser's natural airflow.

The addition of floor strakes and slots ahead of the rear wheels by the teams has become common place since the teams started utilising 'Coanda' exhausts. These help to manage the airflow coming around the sidepod, repurposing it, creating vortices that manage the wheel’s airflow pattern reducing the effects of 'tyre squirt'.

Over the last few races I have mentioned Red Bull's adoption of a secondary vertical floor strake ahead of the rear tyre in order to help with this problem but before qualifying in Barcelona the team also revised the area with a 'tyre squirt' slot. The team hasn't raced a solution like this since Monaco last year where it came under scrutiny for placing a hole in the location rather than a slot.

Lotus

Having already subjected the E21 to revisions throughout the fly away races the Enstone team made much smaller alterations for Barcelona: