Finish 'The Ascent' without faulting on the Rattler 125cc bike.
The Rattler 125cc bike is the very first bike you'll unlock and start with. It's statistics are the lowest of all the bikes you can obtain, so having a good run will be a little harder than using a bike higher up the list. It also doesn't make life easier that the race you need to complete is a Hard track.
Head over to the Cutting Edge event to find The Ascent track and load the track up with the Rattler selected. This tracks mainly uphill and to really beat it without faulting you're going to have to keep your speed. Seeing as this bike is the lowest of the low in statistics it's sometime hard to do.
Like some other of the achievements, it maybe worth playing through the track with a better bike to get a feel for it all. Other than that, take your time, keep your speed and make sure you use your posture right so you don't fall or lose momentum!
If you got either the Marathon or Donkey Rider achievements in Trials HD, then this is a piece of cake. Even if you did not get either of those then this achievement is still relatively easy with a bit of practice. The only truly difficult jump I found was in the middle of the track where you have to jump that big gap between the logs. Other than that, be careful and don't watch the time!
The pipes are quite easy, just keep yourself tilted forwards (don't press forward, just set a forward stance and don't touch the tilt controls) and hit full throttle. Just as your front wheel reaches the end of the first pipe, being tilting forwards while still keeping the throttle down at maximum. You should land you back wheel just at the start of the second pipe.
You can also bunny hop the pipes, but I found the above trick easier to hit consequently.
The trick I used for the two logs (the obstacle I had most trouble with) was to rest the bike at the same spot as where you'd reset at the checkpoint just before the gap (the rider's head should be just on the green checkpoint light). Then you go for a "simple" bunny hop, but you need your timing just right. Press full throttle and f
Press full throttle and full backwards tilt at the same time, this should force the bike into a wheelie. Just as the back wheel reaches the vertical "support log" near the end of the horizontal log, switch to full forwards tilt while keeping your throttle down. If you got the timing right, you should clear the gap and might just need to fiddle a bit to keep your balance.
Remember to train over and over again certain checkpoints that causes you troubles, until you figure out a suitable way for you to pass that obstacle. After the log jump just keep your head cool and don't panic; the hard part is over.
also, flickin the thumbstick can be quite essential. The one thing I have found that seems to work (somewhat) is to just relax! Don't loose your mind. Remember how you made it from one checkpoint to another and stick with it. If your hands get sweaty(like mine did) then just pause the game @ a checkpoint or when you can safely. Relax, take a deep breath and continue on a little further. Still working on the "Marathon" cheevo. Really hate it!
Finally got this today. Pain in the arse, but satisfying seeing the achievement pop. Took a while as I got stuck with the quick double jump involving the tyre, but first time I got past that, I completed it. Awesome game, but Red Lynx are sadist as fuck.