A coupla people wanted me to put these in here for 'beginners' to look at, so here they are - series of photos and shit explanations as to how to pedal-up to backwheel, sidehop, and gap (soon, once I get the pics sorted).
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Pedal-up
Roll at the wall like you mean it. Focus on where you wanna land. Bad foot at about the 12 o'clock position.
As you get nearer the wall, start pedalling hard, whilst crouching down over the bars, ready to spring up.
As you pull up and your good foot comes round to the top of the stroke, start really throwing your body up, and lifting the bars up hard with your arms.
Extend your body vertically, meaning you can suck the bike up underneath you higher. Just spring up super hard, whilst still pulling the bars hard.
Throw the bars forwards once the front's cleared the wall fully, and bring the back of the bike up with your hips, knees and ankles. Just suck it up
That should do it, really...
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Sidehops -
I'm not great at these, so it might be a little off...
Trackstand next to the object, and focus on what you want to do. You need to be focussing precisely where you want your front wheel to go (if you're upping to front or 2 wheels), or the back if you're doing it straight to back wheel. Keep focussing on that spot. Make sure you're set up properly, and then just kick to the back wheel.

Do little hops around just to make sure that you're going to get traction and grip, and that it's as good a take-off as it can be, basically. All this time, keep focussing on your landing.

Do a larger hop (just like a backhop, but lift it slightly more so you can drop into the preload). Crouch down, keeping your weight near the back wheel. As you do this, 'cock' the pedal by bringing it back up through the stroke a little. I've also found that keeping your arms a little straighter during the preload seems to work pretty well. If you watch the AndyT vids of Vince, check the technique there. Arms are fairly straight, and he fucking sends sidehops...

Let go of the back brake, whilst again focussing on where you want the front (or rear to backwheel) to go. You give a kick on the pedals as you do this. I've always found it hard explaining when, but most people seem to just know when to do it anyway. Just one of those intuitive things... But yeah, as you start to leave the floor, move your body weight upwards, and slightly forwards. This is so you commit more to the front wheel. Typically, if you focus on getting the front end on, you can kick the back over and onto the wall a little easier. If you look at my head and upper body in the pic, you can already see me starting to move myself more over the landing spot for the front wheel.

Once you've got the momentum pushing your bike over the wall, tuck the back end up, and suck it up with your knees and ankles, whilst pushing it over the top of the wall too. This makes sure that it doesn't just batter into the side of the wall, which isn't too pretty. If you're well into the fashions now, this is the time to initiate that well ott super-tuck pose.

Try as much as is possible to slightly absorb the impact upon landing, just to keep your balance as much as anything, basically. It just helps you keep steady when you land.
You can also turn your front wheel in the direction of the wall too just before you land. Some people find this is useful to tuck the back end in and get their tuck on, and it can also mean you've got more chance of getting some grip on the wall if it's a bit of a sketchy surface (i.e. a non-flat-topped rock, or whatever).
Like I said, I'm not shit-hot at sidehops, but Benito Ros and Vincent Hermance are, so just watch vids of them doing them to get the idea of doing the mahoosive sidehops
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Gapping - Coming soon, probably.
Viddy-ho - "Gap, including slow-mo.wmv" or something like that.
There are several ways to start off doing your gappage. With the vid, it's not a great example 'cos I had to hop into it, so it gave me more momentum. However, you can either hop on the spot, then get settled then launch, or you can do it one hop to your take-off, then use that momentum to sail further. It's up to you - it's the same as with sidehops.
Anyways, assuming you're going to do the many hops technique, we're away
Hop to the edge of where you want to go from. Really look down at the edge of the take-off. This'll help you place your bike in the best place possible, so you can send it good 'n' proper. For good technique, ref. the section where they're riding Paris in the AndyT Koxx vid, and check out Benito Ros. Hops for a while looking straight down, knows he's in the right spot, looks up, spots landing, kicks, and leaps over half of Paris. That's what you need to aim to do, especially if it's on natural 'cos although you can feel to some extent where you are, you can see other potential pitfalls around you.
When you get to the correct spot, you need to do a pre-load hop. Hop the bike a little higher than you normally would, and instead of absorbing the impact (like you would just backhopping), force the wheel down more. This is where going from the edge can help, as it forces your tyre away, making you gap further. However, this technique means you have to focus more on going upwards rather than forwards. Anyway, just do the preload hop. As you land, keep your weight over the backwheel/BB area, and lower the front whilst cocking the pedal back however much you need to.
/\ That's why you keep your weight fairly far back. You really need to kick on the pedals and throw yourself into the bars with your hips to get it moving. As they always say, you weigh more than your bike, so get yourself moving and your bike will follow. As you kick off, simply move your weight forward as hard as you can.
As you pass through the air, you need to suck the bike up more with your legs to start the transfer from having your weight over the bike to having your weight behind it. Basically, suck the back wheel up, whilst lifting the bike upwards and forwards with your arms.
When you start to get nearer to the landing, you need to start moving your legs out straight, placing the back wheel in front of you. This will absorb the impact, and it's also the time that you can precisely position the back wheel if you're gapping onto something narrow or you have to be very accurate. It's also the completion of the movement you have to do with the bike - if you look at it, you start off with your body being thrown forwards, then it's like the bike catches up and goes off in front, which is pretty much the best way of thinking about it.
Extend your legs fully, as well as your arms too to keep the front high if you want to keep it on the back wheel or just to keep in control in general, and absorb the landing with your legs. This is the point which will decide whether you land it and keep your wheel round, or land it and give it a tasty flat-spot. The decision's already been made for you if you're running the new Echo rims though, so just do whatever 'cos it'll flatspot anyway
That's pretty much how to gap, really. Just watch the vid, watch vids of Benito, Vincent, etc. (Probably more Benito, 'cos he seems to exagerate the movements more because of the bike he's on. Vince just seems to sail stuff, which I guess is the thing to aim for).
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Upping to front - Note: this isn't mad high, but for higher walls you simply end up going upwards for longer, and just preload and fire up more explosively. We happened to have a 6 pallet stack, and I thought I might as well just get it in the bag. It's also possible to do it from static, but it's generally done like this. For static, just go from the "preload" section onwards, but give it some more effort 'cos you won't have the speed from the run-up...
Again, I'm not amazing at this move or anything, but it'll hopefully help someone out.
I find going just about or just below backwheeling pace helps with this move. Also, 'cos I kink it left when I do it, I start a little right of where I want to end up. So yeah, rolling along, bad foot forward. Do a half pedal stroke as though you were doing a really small rolling gap so you land with your back wheel on the floor just over a bikes length from the wall (not exact, but you get the feel of it with time).
At this point, I've crouched down and preloaded for the move, similar to a sidehop. You crouch down with your weight leaning slightly towards the wall. Again, for all of this move, keep your head looking and focussed on where you want to land. The more you do it, the more accurate you'll be, and it'll just make you do it better in general.
Anyway, you've now preloaded, so you now need to give a bit of a kick on the pedals. This doesn't need to be super severe because you've built up some speed from the roll-in. However, you also need to begin to commit to the front. This is the make or break part of the move.
As your bike starts to lift up as you kick on the pedals and lift it up with your arms and legs, move your weight over the front, to where you want your front wheel to land. It helps to bend your arms to bring the bars up towards you, and so you can place it on the wall more accurately. FOCUS on where you want to land. Really commit to the move. It's pretty much the only way to get it done - if you don't, you'll either have your weight too far back and your tyre or brake will slide, and if they don't you still won't make it up, or you'll plough into the wall. Neither's cool.
Apply the front brake.
As your front tyre hits the wall, you need the brake to be either fully locked, or pretty hard on. With your weight over the front tyre, you then need to release the brake, and throw your arms forwards. As you do this, suck the back tyre forwards and onto the edge using your knees and hips.
After you've whipped the bike forwards, you'll either end up on the back wheel (if you've got your weight far enough back and thrown the bars up correctly), or just to two wheels. Either's good
But yeah, the hard parts are commiting to the front, and then getting that flick to back wheel. You can practise this fairly easily anywhere - just do a little gap to front, land with the front brake on with your weight over the tyre, then just lift up the front whilst modulating the brake, and bring the back wheel forwards, underneath you.
This is a pretty sketchy description, so if anyone's got anything to add I've missed, or want me to put any more about one phase, let me know.
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Wheelswapping
There are many versions of how to do this - back brake off, front brake off, both brakes off, both brakes on - so just go with what you prefer. Some say back brake off means you can "compress" the bike more and get more fork flex and so on, but personally, I prefer the more control of having both on. You can still compress the tyres and flex your bike to hell if you want, and the end result's the same, plus your back tyre stays where you want it if you're riding natural and you're doing this on sketchy terrain.
Get your front wheel up onto the top of the object. Hop around as much as necessary to get your balance. One of the key things to remember is to turn your bike so if you drew an imaginary line from the centre of one pedal to the centre of the other (or "center" for the non-UK people

), it'd run parallel to the wall, e.g.:
This means the bike is as close to the wall as possible, and thus easier to get up. Think about it like how you do an "American" bunnyhop instead of lifting two wheels at a time
Anyways, you're now in the correct position, pedals level, close to the wall. Now, keeping your weight firmly above the headtube/front wheel of the bike, crouch down to preload.
Things to note:
'cos I'm a fatty fat fat fat, my tyre's compressed. This is all good. Equally, my arms are bent, so I can spring up as far as possible. This isn't like a lot of trials stuff which is all balance and technique, this is just brute force. You're hoping to send the bike up there just using your body weight, so really crouch down - bend your legs and arms. As you do it though, like I said, keep your weight over the edge of the wall/front of bike. Leaning back = nono.
Spring up. As you do so, just lift the bike straight up. You're not throwing the bike across or anything, you are just focussing on lifting the bike straight up. The way that you get the bike across and onto the wall is that as you're lifting the bike and your own body by throwing yourself up in the air and jumping with the bike, you throw the bars forwards, and tuck the back tyre up underneath you on the wall. This means all your efforts go into getting the bike forward for max height, and that you also still get the bike up there without nailing the back tyre into the face of the wall or anything. In that pic above, the bike is already lifted up level with the wall, so all I have to do is throw it forwards. If it helps you get your head around it, you should aim to end up as though you've just backwheeled the wall, that same sort of crouch/tuck position.
And there you go. You end up as if you've just been backwheeling, so just deal with it in the same way. Try and raise your body up asap, and get the bike up on the back wheel and in control. Alternatively, just let the front end drop and land it to two wheels.
Trashzen pwns all this stuff though, so you might wanna go check out
www.trashzen.com (I think that's the site).