I have all 70 achievements so i know what ill be talking about.
First off, the two best bikes are cycle king and farty pants(gay name but still). The reason these are the best is because the king is the best at wheelies and farty pants is a fliper. (Hint: farty pants makes front/back flips too easy, my personal best is a multiflip frontflip, witch is basically 6 frontflips at once)
now for the hardest achievements,
-Sneaky start, absolute hardest one, what you do is the following. Start the level you get the achievement from and dont touch any keys, right before the word go apears(i mean when get set disapears and go almost apears) press and hold the right and top keys(or d and w), then instead of go itll say sneaky start, if done correctly just complete the level so it counts.
-another one people are finding hard is 'moon bonus level-wheelie', i did this pretty easily. choose the king as your biker and the second the race starts do a backward wheelie, dont go fast just try too stay near the start(dont worry if the rest of the racers get a head start, ive given them a 30 sec head start and still come in first on the moon) now if you cant get the 10 secs before the first ramp restart the level and try again, that simple, when u get it win the level in atleast 19th place.
last thing, use farty pants for everything that dosent need a wheelie, with him you can do a frontflip just jumping, a triple frontflip from a normal ramp a quadruple frontflip from a really good ramp, a quintuple frontflip on a really good ramp with some boost and a multiflip frontflip with the right conditions(6 flips) usually with this guy i keep a boostx5 throughout the levels.
I don't find Sneaky start hard - I can do it 80% of the time.
The hardest one for me were: 1. 10 sec rear at once on moon 2. 40 sec air on planetoid 3. 75 collecting thingys
At the beginning any more boost than 1x was hard - but atm. I can achieve 5x with almost any char (not counting that double-bike dudes) at almost any map - easily.
it's true that farty pants is better spinner and his front doesn't go up when speed is high, however Colin has lower chassis and it really helps. Colin is better at rear wheeling too.
-Cycle King: Backwheelie Pro -Sir Colin: Best Back Somersaults -Spoke: Backwheelie Pro -Farty Pants: Best Front Somersaults -Letter F: Frontwheelie Pro
Actually I think that Sir Colin is just like the best...other than for front wheelies. He can backflip,frontflip, and backwheelie just as same as other even better maybe! But this is just my suggestion and opinion!
As all bikes are different you have to choose the right one for the types of achievments in the race. Say if you have to do "15 seconds worth of rear wheelies" you wouldnt use any vehicles like the one with the big front wheels. etc.
