I've been trying to get the riff shown below down for the past few weeks, but it has always caused me trouble. Whenever I try to practice this riff faster than 130-140BPM, I have a hard time switching from the E to the A string and from 16th notes to 8th/quarter notes. Upon switching strings and note values, my picking hand would go out of time and lose the Down/Up/Down/Up alternate picking cycle.

What can I do to help keep my picking hand in time and from losing the alternate picking pattern in such instances? Any advice or exercises I could practice would be greatly appreciated.

Here is a sample of me playing the riff at 100, 130, 150, and 170 BPM(If it helps.)

(Branding of) the Gears by Dethklok(195 BPM)[How I play it.]

-----S S S S S S S S S S S S E -E --- S S S S S S S S S S S S Q
-----D U D U D U D U D U D U D -U --- D U D U D U D U D U D U D

--S S S S S S S S S S S S E -E --- S S S S S S S S S S S S Q
--D U D U D U D U D U D U D -U --- D U D U D U D U D U D U D

Q - quarter
E - 8th
S - 16th

D - Down stroke
U - Up stroke

Areas where I have trouble

Thanks in advance!
That's good old inside the string picking. Try starting with an up stroke instead of down. Use a metronome and go slow.
Quote by Geldin
Junior's usually at least a little terse, but he knows his stuff. I've always read his posts in a grouchy grandfather voice, a grouchy grandfather with a huge stiffy for alternate picking.
Besides that, he's right this time. As usual.
practice just the E to A skip going 0(e)-1(a), 0(e)-2(a)...all the way up the neck. if you get what I mean. Otherwise jsut the usual start slow and work with a metronome
That's not tremolo picking, it's just fast alternate picking.
Actually called Mark!

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