Belgian national champion Philippe Gilbert showed his class by securing his maiden men's world road race title as Australian cyclists missed out on the medals for the first time in four years.

Gilbert cracked the field on the final climb of the 267km race in the Netherlands with a stunning burst up the Cauberg to leave Norwegian Edvald Boasson Hagen second ahead of Spain's Alejandro Valverde.

Allan Davis was the best-placed Australian in sixth with compatriot Simon Gerrans 21st.

Gilbert, who last year became only the second rider to win all three Ardennes one-day classics in the one season, only recently returned to form following a slow start to the year.

Italy's Vincenzo Nibali led the riders up the Cauberg before Gilbert launched a blistering attack that caught his rivals off guard.

"When Gilbert set off, I couldn't get onto his wheel, I was a little too far back," Boasson Hagen said.

Sunday's results ended Australia's good run with Cadel Evans winning the 2009 title, Davis claiming bronze in Geelong two years ago and Matt Goss collecting silver in Copenhagen last year.

"He's (Gilbert) a deserved world champion," Davis said.

"All knew what he was going to do, what the tactics of the Belgian team were going to be.

"He was just too strong."

Gerrans had been rated Australia's best hope before the race but said he was not quite up to the task.

"You can't be too frustrated when you haven't got the legs," he said.

The hilly Limburg course proved too much for big-name British riders Mark Cavendish and Bradley Wiggins, they both failed to finish.

The route did not suit defending champion Cavendish while Tour de France champion Wiggins rode in support of his countryman.

Earlier in the day, Caleb Ewan sprinted home for silver in the junior men's road race as Australia finished the world titles with three silver and one bronze.

Cycling Australia national performance director Kevin Tabotta said it had been a "reasonable campaign".

"Sixth in the men's road race, first time in four years outside the medals so a little bit disappointing that we weren't there in the medals again," he said.

"But the boys rode incredibly well."