The 2018 FIM Trial World Championship scales new heights this coming weekend with TrialGP Andorra, round three of the series high up in the Pyrenees principality at Sant Julia de Loria.

With the highest point of the Trial at sixteen-hundred metres above sea level, only TrialGP France in the Alps next month can match it when it comes to altitude, but it is attitude that will count with the championship wide open after the opening two rounds.

Advances in technology mean that all engines should run smoothly at such dizzy heights, but the riders could still struggle in the thin air.

At this stage in 2017, Toni Bou - Repsol Honda was heading into TrialGP Andorra with an unbeaten three-from-three record, but twelve months later it is a vastly different story and the eleven-time World Champion has won just once following May's opening round in Spain and Japan's double-header at the start of June.

Bou is still leading the field, but he is only a couple of points clear of a two-way fight for second between his fellow Spaniards and Gas Gas team-mates Jaime Busto and Jeroni Fajardo who are tied after taking a win apiece at Japan's famous Twin Ring Motegi circuit.

A spinal injury sustained at an indoor event in France earlier in the year has had an adverse effect on Bou's form, but he is determined to finish on top.

"In Japan I didn't have such good feelings," he said. "I had a relapse in the back injury and I was not well. This told us that this year would be complicated."

"We have been working on my back and although I am quite happy I have had some discomfort, but less than when we started the World Championship.

"I hope to have a good Trial. I want to get a good result and it will be very important to be on the podium to get points for the championship. It will be difficult to win, but we will have to make the most of it."

Last year Bou was third in Andorra, where he now resides, behind Adam Raga - TRRS and Busto whose second-placed finish marked a career-first podium for the twenty-year-old and this time around the result will be crucial.

If Bou fails to win he may lose the championship lead, but if he does come out on top he will reassert his dominance which could set him up for an incredible twelfth consecutive title.

Take Busto and Fajardo out of the equation and Bou's main challenger must surely be Raga. The two-time World Champion has not had the greatest of starts to his 2018 campaign, but the confident Catalan - who is currently sitting in an unfamiliar fourth in the points table - is always a threat.

Realistically, the top four should be the favoured candidates for a podium finish in Andorra, but you can not rule out the Spanish duo of Jorge Casales - Vertigo and Albert Cabestany - Beta, Japanese fan favourite Takahisa Fujinami - Repsol Honda and Britain's James Dabill - Beta.

The Trial2 fight continues at TrialGP Andorra where veteran Italian Matteo Grattarola - Honda already has a healthy nine-point lead over eighteen-year-old British prospect Toby Martyn - Montesa and a further nine-point advantage ahead of Spain's Gabriel Marcelli - Montesa.

After dropping down from the TrialGP class where he finished tenth in 2017, on paper at least thirty-year-old Grattarola should be a clear favourite but he was beaten on day one in Japan by Martyn and has a big target on his back for anyone trying to stake their claim for a place in the premier division next season.

The field is completed by the Trial125 class where Britain's Billy Green - Beta currently holds a four-point advantage over fifteen-year-old Spaniard Martin Riobo - Gas Gas whose compatriot Pablo Suarez - Gas Gas is another seven points adrift.

Green, the Vice-Champion in 2017, won the opening round in Spain and day two in Japan but he has to be consistent - and he was not on day one in Japan when he finished fifth - if he is going to be crowned the inaugural FIM Trial125 World Champion at the end of the year.

Follow all the action from TrialGP Andorra as it unfolds over the weekend, with full coverage across all the official TrialGP social media channels, on TrialGP.com plus live qualification on the TrialGP Facebook page.