So.. The tilte explains my problem I guess, I can't get my alternate picking under control.
I've been playing for over an year now, and I've played all kinds of metal songs with downpicking (or tremelo picking ofcourse). Master of puppets, hand of blood, tears don't fall, figure number five, no problem at all.
Although now I'm trying to get at a higher level of playing, I need to stop using only downpicking, as I'm working on "Technical Difficulties - Racer X" now, I notice I won't make it with just downpicking.

I can downpick simple solo's as the intro solo of "Welcome home (Sanitarium or the intro solo of Fade To Black" Both by Metallica.
Although I can't play anything faster with alternate, it get's sloppy and uncontrolled, even after hours and hours of practicing alternate picking.

So, has anyone got the same problem, or knows how to train it so I "can" play anything faster?

It's probably just due to your bad habits of only practicing downstroked to date. I've had similar problems and I'm steadily getting over a lot of my bad habbits by just slowing everything down a lot then playing it to speed. After a while I get better at it but it does take patience.

Don't worry if it sounds bad when you're practicing because that is what you're doing, practicing, not playing.
Dave Tither
Quote by chrisbeevor
You need a metronome.

I don't think they're necessary.
Dave Tither
I have the same problem, i think its just because your used to playing fast downstrokes its hard to slow down for alternate picking
Manchester United
Do scales with alternate picking? Do it slowly and steadily making sure each note rings. Once you have the hang of it increase your speed
Start slow (very slow), and increase the speed with the time. A metronome should help.
yeah man i had the same problem, you got to take it real slow just like the dude above me said, and just build up speed from there. The timing then comes with practice.
Practice, practice, practice!

There's no short-cut, you just have to do it.
Try practicing with a metronome, and start off really slow, with an easy easy song. Then do the same with a slightly harder song, and make the metronome faster as you practice is, just keep practicing these little things and eventually you'll work your way up. The same happened to me, keep going dude.