Ahead of this weekend's US round of the World Superbike Championship, Castrol Honda completed a two-day test at the same Miller Motorsport Park circuit.

The team nominated Miller as its 2011 test track after struggling at the venue last season.

Jonathan Rea and Ruben Xaus used the Sunday and Monday test to debut new parts for their CBR1000RR machines, including a new swingarm and suspension components.

Although the test was affected by bad weather, Rea couldn't fault the Ten Kate team for the range of new parts.

"We nominated Miller as our test track this year because last season we really struggled with bike set-up," confirmed Rea, who is fourth in the 2011 championship, with one win, after four rounds. "I really enjoy riding here in America but the bumpy nature of the track makes it very difficult to find the optimum settings for the bike.

"My team have pulled out all the stops though, and we had a lot of new items to test. The weather wasn't on our side, so the track conditions were pretty dirty out there. I found a better feeling for corner entry with a new swing-arm and this really helped the feeling when the tyre life starts to drop.

"I also had some new suspension items to test and, while we found some positives, it will take more time to get it dialled in properly. We are in much better shape now to start the weekend and as always we will do our best."

Team-mate Xaus - 15th in the championship at present - had a more complicated test, but believes he eventually found a good base set-up.

"We know that Miller has some difficult features because it's very bumpy due to a lot of cars using this track. We experienced a lot of chatter on the first day which we struggled to find a solution for. I tried to adapt my riding style a little to improve the lap times but unfortunately had a small crash in the afternoon which stopped our progress," he explained.

"The morning of the second day we worked hard to improve the set-up and lap times in between some pretty bad weather conditions and in the end found something better. We tried a new brake system and a softer chassis which made a really positive step forward, as well as helping me find a longer life for the tyres, which is really important for this track. I'm pleased to say that I finally found a good base set-up for the race weekend so hopefully I can help to push the whole team forward."

Team manager Ronald ten Kate was pleased with how the new parts performed, although more track time is needed to perfect the settings.

"We brought a lot of new parts to this test which included a complete new swing-arm and different front forks. In the few dry hours we had over the two days we set them up as best we could and everything was quite positive. However we really needed more time to test on longer runs to get a precise set-up and fast lap time," said the Dutchman.

"It's really a pity the weather was what it was, however we can take the progress made from this test into the race weekend without any hesitations, as the new parts were simply a lot better. Despite the weather and restricted track time, I'm still positive about the overall results of the test and we look forward to Saturday's first practice session."

The fifth round of the 2011 World SBK series will take place at Miller on Monday 30 May, which is Memorial Day in the USA and a public holiday.