I know this is a very old thread, but this seemed the best place to stick some info I just learned related to strength of the LHT frame (related to the OP's off-road experiences question). In short, the 2014 LHT frame is built to withstand tougher conditions (as defined by ASTM F2043) than the 2014 Cross Check. I understand the LHT needs to be tough to haul a load. What I don't understand is the Cross Check, a supposed do-anything go-anywhere bike, based on a cyclocross geometry, is rated as a comparative lightweight. Maybe in recognition that most people don't go off road nor load it down.
By these definitions,
if the LHT geometry allows, you could go into rougher territory more safely on an LHT.
Surly's
Bike and Frames page has PDFs for their frames and forks. The LHT frame/fork is rated a "3", the Cross Check a "2". Here are the definitions:
Conditon 2 (Cross Check):
This is a set of conditions for the operation of a bicycle that includes Condition 1 as well as unpaved and gravel roads and trails with moderate grades. In this set of conditions, contact with irregular terrain and loss of tire contact with the ground may occur. Drops are intended to be limited to 15cm (6˝) or less. Please see link to Bike Owner’s Manual on surlybikes.com/safety
for complete list of riding condition descriptions.
Condition 3 (LHT and Disc Trucker):
This is a set of conditions for operation of a bicycle that includes Condition 1 and Condition 2 as well as rough trails, rough unpaved roads, and rough terrain and unimproved trails that require technical skills. Jumps and drops are intended to be less than 61cm (24˝). Please see link to Bike Owner’s Manual on surlybikes.com/safety for complete list of riding condition descriptions.
The LHT has a larger diameter TT than CC. This was an intentional design feature of the original (2004) and all subsequent LHTs, Trucker Deluxes and Disc Truckers. A larger diameter tube is stiffer (tube stiffness increases as a cube of tube diameter). A stiffer TT is desirable on touring bikes to minimize the likelihood of shimmy, an undesirable phenomena which sometimes manifests on heavily/improperly loaded (touring) bikes.
The LHT also has a heavier-duty fork {again larger diameter - fork legs) than the CC/Straggler/any other Surly "road" frame.
The combination of TT and fork makes the LHT closer to a rigid MTB frame WRT to off-roading capability, and is the reason the LHT is classified Condition 3 by ASTM F2043.
The LHT takes slightly larger tires too - this may be a factor as well in the F2043 classification.