Lewis Hamilton fears taking a step backwards in Barcelona on Sunday after revelling in his giant leap forward in Bahrain.

With the 'lie-gate' saga now behind him, the weight is finally off the shoulders of the world champion and he should feel more at ease throughout the Spanish Grand Prix weekend.

Finishing fourth at the Sakhir circuit 11 days ago also suggests McLaren's painful teething problems at the start of the season are now behind them.

However, his optimism and that of the team is tempered by the fact the car already sports a number of new parts following a round-the-clock effort that saw them installed for China and Bahrain.

McLaren are expecting only another small step over the next few days, in contrast to their rivals who will be unveiling a considerable raft of improvements designed to propel them forward.

Throw in the fact the McLaren is not expected to perform well on the high downforce Circuit de Catalunya, and it could be a tough weekend for Hamilton and his team.

"After such a positive performance in Bahrain, we're fully aware the characteristics of the Barcelona track won't suit our car so well," remarked Hamilton.

"In addition, we won't have the bigger upgrades of some of the other teams as we introduced several new parts during the opening flyaway races, so it will be interesting to see where we sit in the order.

"Nevertheless, the engineers are optimistic our new diffuser and front wing will again help us to make progress towards the front of the grid."

Team principal Martin Whitmarsh, also free of the shackles of the scandal that dominated the sport for several weeks, can appreciate Hamilton's comments.

With McLaren racing under the threat of a suspended three-race ban, Whitmarsh knows his team have to be whiter than white from now on, but is confident they can build on the progress seen in Bahrain.

"Our decision to introduce performance updates at each race rather than concentrate all our developments into a single upgrade package helped us score some reasonable points in the opening flyaway races," said Whitmarsh.

"With our rivals expected to introduce some more substantial improvements in Barcelona this weekend, we again expect a fight to score points.

"But while the high-downforce nature of the Circuit de Catalunya may show up some of our car's shortcomings, everyone within the team remains confident and motivated we can sustain the momentum we have gathered to push and close the gap to the front this weekend."