Having already completed its European leg, and immediately after the inaugural Argentine round in the South American continent, the 2013 FIA World Touring Car Championship visited Sonoma Raceway in the United States for its ninth round. This was the second time for the championship to hold the races in this well known American race track which has also hosted the IndyCar and NASCAR races for years.

As the season reached its closing stage, attention was naturally focused on the title contentions. When the American round began, Yvan Muller was leading the drivers' championship by a considerable margin and it was almost-certain that Honda would secure the manufacturers' title in its first attempt.

As it was a fly-away event, the race weekend began with the test session on Friday. Throughout the sessions from Friday to Saturday, the leading cars and drivers performed equally well and no one was able to dominate all sessions.

Tiago Monteiro in one of the factory Honda Civics was the fastest man in the Friday's test session. After this Sonoma round, the Civic WTCC car will reach its first anniversary, as the car made its debut in the championship at the Suzuka round last year. So the Japanese manufacturer wanted to have good results here to return to their home races in a positive mood. Robert Huff in a SEAT Leon was also fast in the test session, only 0.132 seconds behind from the Portuguese.

On Saturday, Pepe Oriola set the fastest time in the first practice session and led the all Chevrolet top three with Tom Chilton and Muller. However, in the second session, the Frenchman put his name off the top of time sheet. Then Norbert Michelisz in a Honda Civic followed with a only 0.031 second gap and Hugo Valente, driving one of two Campos Racing run SEAT Leons, came in third, 0.350 seconds behind the session leader.

So it looked quite difficult to predict who would be the man to beat in the qualifying session. But, after all, the man who was closest to the drivers' championship title, Muller, clocked the fastest time in Q1, 1'45”941, and he was the only driver who completed the qualifying lap in less than 106 seconds. The manufacturers' title favorite, Honda, was also strong, as Monteiro ended the session with the second fastest time, 1'46”340, followed by the Zengo Motorsport driver, Michelisz, who came to third with 1'46”346. Among the SEAT drivers, Huff and his German teammate Marc Basseng made their ways into Q2, as they set the sixth and eighth fastest times. The Lada drivers, James Thompson and Mikhail Kozlovskiy, failed to end Q1 within the top twelve.

The RML Chevrolet drivers were the dominating force in Q2 that was fought by the top twelve qualifiers from Q1. But for this time Chilton was faster than his ex-champion teammate and secured his first pole position in WTCC. Following Muller in second, Monteiro took the third grid for Race 1. The reverse grid rules meant that Mehdi Bennani in a BMW 320 TC was given the best grid to start Race 2.

It was bright and clear on the race day. Compared with the last year's record, the air temperature was a little lower ? 24 degrees Celsius ? but the track temperature rose to 34 which was about 2 degrees higher than last year. Race 1 began with the rolling start procedures with the pole sitter, Chilton, on the inside, alongside of Muller. When the red signals went off, however, the Honda drivers behind them got slightly better acceleration. So Monteiro, starting from the second row, managed to get ahead of Muller at Turn 2, while Gabriele Tarquini passed Huff to move up to sixth.

Monteiro quickly closed the gap with Chilton and caught up to the Chevrolet driver at the final corner of Lap 4. But the 28 year old Briton didn't give in to the pressure from behind and kept his lead position firmly.

In the middle of the field, Tom Coronel made a remarkable start from the 11th grid. He passed Basseng on Lap 2 to come up to eighth and then started the fierce battle with Huff for seventh. On Lap 8, the Dutchman tried to squeeze his BMW into the space inside of Huff through the technical section of the track but the reigning champion fended off the attack. Two laps later, however, Coronel made his second attempt and this time the move was successful even though there was slight contact between them.

At the front, there was no more action after a few position changes during the early stage. Monteiro stayed within a second from Chilton for a while but, as the race leader started to push a little bit harder in the closing stage, the gap between them grew to 1.258 seconds on Lap 10 and the Portuguese could never cut it down again. Thus, Chilton claimed his maiden victory in WTCC, leading Monteiro by 2.161 seconds when the checkered flag fell. Muller finished the race in third and added some more valuable championship points.

The YOKOHAMA Trophy class was won by Alex MacDowall who started the race from the fifth grid and finished it in fourth. With his main championship rivals, James Nash and Michel Nykjaer, ending the race in second and forth in the class respectively, MacDowall could close the point gap with them.

After having a two hour break, Race 2 was about to start. The starting grids looked quite interesting because the cars on the top three grids were from three different marques, as Bennani's BMW 320 TC sat on the pole position, followed by Tarquini's Honda Civic and Huff's SEAT Leon.

As is often said, BMW 320 TC has a theoretical advantage in the standing start, which is adopted for WTCC's Race 2, because of the car's rear wheel drive layout. But, for this time, Tarquini's front wheel drive Civic was superior in the acceleration from the grids. Although Bennani narrowly defended his position at Turn 1, when they were exiting the corner, the Italian's Honda was clearly faster and had better acceleration on the uphill section to Turn 2. So it wasn't too difficult for Tarquini to pass Bennani at the corner and become the race leader.

Huff also put heavy pressure on the Moroccan from behind but the BMW driver didn't give way easily. Then the Briton's effort to get ahead of Bennani backfired. He briefly went off the track at Turn 7 on the next lap, when he was still pushing his opponent very hard, and soon dropped out from the contention because of the damaged tires.

This handed the third place to Michelisz and now he joined the leading group, together with Tarquini and Bennani. About two seconds behind them, Nash was running in fourth and was leading the close five car pack that included Muller, who jumped up from the ninth grid, Monteiro, Coronel and Basseng.

As Nash's pace wasn't very good, and he blocked the others in the pack, the gap between he and the leaders was gradually growing. At Turn 7 on Lap 4, however, Muller made a brilliant move and passed Nash from the inside and Monteiro followed his path at Turn 11. Then they started to pursue the top three very hard.

At the end of Lap 8, Michelisz led Muller by 2.188 seconds but the gap was reduced to 1.469 seconds one lap later. On the other hand, Tarquini was steadily pulling away from Bennani to strengthen his position as the race leader. In the closing stage of the race, while the Italian was comfortably ahead of the rest of the field, Bennani, Michelisz and Muller formed a close pack, fighting for second. On Lap 11 of 13 lap race, the Frenchman tried to pass Michelisz from the outside of Turn 7. They went through the subsequent technical section almost side by side but it didn't lead to any position change.

So, after becoming the leader on the opening lap, Tarquini's position wasn't threatened at all and claimed his second win of the season, since the Slovakian round in April. Bennani finished the race in third overall and won the YOKOHAMA Trophy class for the third time this year. The remaining place on the podium went to Michelisz who managed to defend his position from Muller's attack. With Tarquini's victory and Michelisz's third place, Honda secured this year's manufacturers' championship title.

WTCC visited Sonoma Raceway for the second straight year. The track surfaces are rather aged and the racing lines on them has been polished up by rubber of tires. Because the grip level wasn't very high, the amount of load put on the tires was relatively low but the wear rate could be higher. Another distinct feature of the track is the undulation. Because of this, the vertical load on tires could sometimes be lost independently on the front or rear axle, which made car control difficult. Some drivers seemed to steer too much in their attempt to recover from such a situation, and it certainly affected their tire wear, but didn't cause any tire-induced problems.

The Honda drivers performed well here in Sonoma, as Tarquini won Race 2 and Michelisz finished the race in third, with Monteiro taking the second place in Race 1. Since its debut at Suzuka last year, Honda Civic has just experienced all WTCC venues in this U.S. round and the car's progress was obvious. For example, the balance of tire usage between front and rear axles was definitely improved and the car has become to use the rear tires more than before to have a better handling balance. This also reduced the tire wear and the drivers could keep a good pace until the final laps of the races. So it was safe to say that the car improvement led to the Civic drivers' good results that secured the manufacturers' title for Honda.