How do you do the the long grind in the hardcore challenges? I've saw a few comments on this site and they seem to be talking about a different area. Do I need to grind all the way down without touching the ground cause that seems pretty impossible. I've saw a few comments that you can manual to each fence but that don't work.

That grind is tough, but not impossible. You basically have to start a the top of the hill, get some good speed, and hop on the very start of the second rail- if you start later than that, you will not make 525 feet. If you are going fast enough, you can jump from one rail to the next while you are grinding.

Some rails aren't lined up perfectly, so you have to lean before you jump, so you can land on the next rail.

Good luck! This took me a while.

Actually, it's easier to start at the bottom.. If you grind up and manual between the rails, it will link the distance and make it much easier to transfer between the rails. Takes a little practice to get down, but it's definitely not hard to do.

Actually, I find myself being turned around automatically because I always waste out of speed before I reach top.

the best i got was 200 feet it is so very very hard.

Everything you need is in this thread: http://www.neoseeker.com/forums/index.php?fn=view_thread&t=120708