Factory Yamaha riders Ben Spies and Jorge Lorenzo both have their sights set on a podium finish in Sunday's Aragon MotoGP.

But while Spies is happy with his pace, after qualifying behind the Repsol Hondas of Casey Stoner and Dani Pedrosa, reigning world champion Lorenzo admits he is struggling.

A set up change mid-qualifying helped Spies claim his fourth front-row start of the year, albeit 0.704sec from Stoner.

"The whole weekend has been pretty good for me, I'm pretty happy with it," said Spies. "We struggled a little bit this morning but the bike's working really well. We looked over a bit of data and tried to find the best compromise. We found it with 30 minutes to go in qualifying and with the race tyres we were about third or fourth quickest.

"When we put the softer tyres on we were able to go quicker and get on the front row. The crew has done an amazing job to get the bike where it is, we're just lacking a bit of speed from the front two guys. We're going to try and challenge for the podium tomorrow."

Lorenzo, who trails Stoner by 35 points in the championship, will start from fourth on the grid after lapping 0.819sec from pole.

"We struggled here last year and we are here struggling again this year, maybe even more. We have many problems with rear grip; we are not getting enough traction to be really fast," Lorenzo explained.

"Tomorrow I think the maximum we can get is third place on the podium unless something very strange happens so that is the goal we have. The long straight is not the best for us but in the corners we are also a bit slower than the others so we must find something."

The four Yamaha riders were left at the bottom of the top speed charts in qualifying.