Did your Duratrac's feel spongy at first?

Well if you're running 30 PSI I can't think of any tire that won't feel spongy. I'm running 38 psi because I live in the hills. There is no spongy or body roll feeling whatsoever. The ride is GREAT.

 

Softer rubber from being Winter rated. Deeper tread depth and large seperate tread blocks will give it a spongy feeling.

I've heard of them being like that, and even my Mickey Thompsons felt like that going from BFG ATs.

 

Whats a chaulk test?

Haven't heard that term before

 

Probably experiencing some "tread squirm" with aggressive widely spaced lugs you will feel some floating with even small steering corrections and this will diminish after the first 6 to 12 months.
Also, my 265-75-16 DTs returned awful mpgs throughout the first summer and dropped from 21.5 with worn out 245 HTs to 17ish. Now with a year and 10k on em I've gotten 20.1 out of the last two tanks with warmer weather/ambient temps.
Chalk line test: draw a line across tread at given pressure and drive a bit hop out and look where line is wearing. If only worn along outer part of tread = pressure too low. If chalk rubs off on center of line first = too high. Also I've used masking tape.

I run mine at 38 rear and 40 front for acceptable chalk test/footprint and maximum mpgs. Downside is definitely jitterier ride and skiddish behavior with hard braking. Air down to 22 to 25 psi for trails and grips and climbs like a champ.