Originally Posted by RCMoeur

Given that I have 5 hitch receivers on 4 vehicles (the Mighty Truckasaurus has them both front & rear), I thought I'd contribute.

If your vehicle has both Class I (1 1/4") or Class III (2") hitches available, I'd get the Class III version for greater capacity and flexibility. Most 1 1/4" hitch bike racks I'm familiar with come with a 2" adapter. And you never know when you might need to actually tow something.

That being said, many compact & smaller passenger vehicles only have 1 1/4" receivers available. I think this is to discourage the use of the vehicle for towing something it shouldn't. Admittedly I could rig up adapters and attach my 26' Argosy travel trailer to the Class I hitch on my Yaris, but even with a weight-distrributing hitch the result is likely to not go well.