Rob Wallace

I'm looking at a new Colorado or Canyon to tow my camping trailer. My trailer is 4600# dry and am assuming an additional 1000# in extra weight from propane, batteries, gear and such. I want the diesel. There is a huge tow rating difference between the ZR2 (5000#) vs standard models (7600#) Can the ZR2's suspension alone account for such a large difference in the tow rating? Is it because it is that much softer? I like everything about the ZR2 but need the larger towing capacity. Please advise. Thanks.