Tony Hawks Pro Skater HD

To continue 30 seconds after the clock hits zero, you're going to need to grind and perform manuals. Make sure you have balance for those 2 stats maxed out. In the video, I show where I like to go to do the combo.

For this achievement, you'll need to be playing "Marseille" in Career or Projective Mode.

Make sure you have a character with good Grind and Manual Balance.

You'll first need to kill the clock down to zero and once the timer runs out you'll need to start a combo and hold it for at least 30 seconds to unlock this achievement. You do not need to land the combo to unlock the achievement.

The best place to get this is to start by doing a slow grind around all the bowls, until it becomes very hard to balance, then switch to a flat land manual, and hold that for as long as possible.

Please view the video for the best location to get this achievement on the map!

easy way to obtain the 2 minute man achievo after the revert update.
all you have to do is pump between to quaters revert to manual repeatedly, you can come out of the combo and carry on as the video shows.

There are several different ways you can go about tackling this achievement. The most common seems to be the most obvious... but also the most difficult.

You can spend half a minute holding grinds in Marseille and switching to manuals when they get too difficult.

OR

Especially for those with terrible character balance or players that just aren't any good at holding their boarders steady, revert/manual is the easier way to go.
Start off by finding a decently wide half pipe or some conveniently placed quarter pipes. The pools in Marsielle are great for this.
Basically, what you need to do is hit the ramp to start your combo just before the clock runs out, and when you land quickly tap your right trigger and down-up/up-down on the d-pad or left stick to "Revert" and immediately manual into the next ramp. You'll want to repeat this each time you land.

Makes this achievement MUCH easier for people with faster fingers and bad balance.

(Also makes getting combo projectives a LOT easier. I was getting HUNDREDS of thousands of points in the first 30 seconds.)

If you have Projectives unlocked, you can do it there so that you only have to wait 1 minute instead of 2 minutes for the clock to run out.

Max your balance before starting. When the clock gets close to zero, start a grind and hold it as long as possible. Jump off and transition into a manual. You can either try to hold the manual, or do ollies between manuals.

The achievement will unlock whether or not you land the combo. The only requirement is that you hold it for at least 30 seconds after time expires.

I'll start off with the most important point I didn't see in other guides: it does not necessarily have to be one combo. Once the timer hits zero, the game generally tries to slow you down and end the run at the end of a combo, but sometimes you can manage to keep things going with a new combo. If you can, go for it, because it will still count. As others said, it doesn't matter if you land the combo or not; the achievement will pop at 30 seconds even if you're mid-combo.

I found the easiest way was to do a revert chain in one of the larger bowls on the farther end of the map* until it became too difficult to maintain my manual balance, then switch to a grind along the lip of the bowl.

You want your grind to be as slow as possible so that you can prolong it easily. While you're waiting out the two minutes on the clock, practice transferring from a manual to a slow grind.

Practice staying straight in the bowl so you don't shoot out the open side and bail. I recommend avoiding tricks that require pushing left or right on the stick so that you don't accidentally turn yourself too much.

If you're not familiar with reverts, you do one by going up a vert and hitting right when you touch back down. This allows you to continue a combo as you go back and forth between two verts; just flick the stick to being a manual during the revert animation. Your manual balance carries over as in any other combo, so you can only do this for so long, but at least you'll be in the air for a significant amount of time so you can keep it going longer than a normal ground manual combo. I think you have to do at least one trick while in the air to keep it going, but I'm not sure.

*I suggested doing it in the larger bowls because for whatever reason I can't seem to consistently do reverts in the verts near the starting area. I think it's because they're relatively small so there's a smaller window to hit the revert properly.