I had the same curt hitch installed on mine (from when the OEM wasn't available) and see what your problem is. You see that plate it hits in the middle, the one the tow hook screws into, you need to remove that.

I am looking to install a hitch with the only intended use to be hauling bikes. I will be using the thule T2 with 4 bike attachments. The entire setup (bikes and carrier) will not exceed 150lbs. So my question is can the curt handle this.

my friends and I does lots of track days with motorcycle, one thing i see often is thule system offer in motorcycle carrying too, and I don't see why not.

I hoping 2013 brings me some more luck and money lol, I need to get a factory hitch kit by next august to tow our trailer for camping. IMO the factory hitch is worth the money based on what you get, form and function.

First question is what is the actual weight you will be carrying. When I looked it up, the Thule published weight is 115 lbs for the rack (4 bike version), so you have some pretty light bikes there. If you assume that you may one day put a mountain bike or three on there, you could be at 30 lbs per bike, but road bikes will likely be under 20. For calculation purposes, let's use 115 + (4 x 20) = 195 lbs. You can redo the calculation with your actual weights.

From the Thule web site, the CoG of the bikes (not the rack) for the 4 bike version is at 35" from the hitch pin. The CoG of the rack itself is likely a little less that that, but just use the 35" for ease of calculation. So you are applying a bending moment of 195 lbs x 35" = 6825. The BMW spec, for the OE hitch (which is much beefier), is a maximum load limit of 600 lbs tongue weight at a maximum distance of 8" from the receiver pin. Divide 6825 by 8 and you get 853, so you have an equivalent bending moment to an 853 lb tongue weight.

That is why racks are so much harder on hitches than actually towing something. People say "I am just using a bike rack" as if it is less of a load. It is for the fore/aft load, accelerating and braking, but not for the bending moment, or twisting force, and that is the failure mode that we saw for various non-OE hitches; they bent the 2" receiver downwards. Trailers don't tend to bounce on the hitch ball so much, due to trailer suspension and relative inertia of the trailer. They bounce on their suspension more than on the hitch ball. What happens with cargo racks and bike racks is that they bounce every time you go over a bump, and that is when the hitch sees a multiple of the bending moment I referenced above, which considers only a static load calculation. It is why BMW publish a much reduced maximum trailer load limit (50% reduction) if you are towing off road, because of the bouncing on the hitch ball.

So, would you use your aftermarket hitch to tow 8500 lbs? 10% tongue weight is a good guideline, so I just used that to come up with the 8500 lb trailer example. Leaving aside brake issues, and transmission issues, which don't apply at all to this analogy, would you trust the basic hitch structure? If so, no problem with the bike rack. I wouldn't, myself, without the OE reinforced hitch. I think a two bike rack, with road bikes, would be much less, but it is still worth considering the impact.

Suggest you do the calculation yourself with your actual weights and distances, my calculation above is provided as an example. You may be carrying less weight, closer in to the vehicle, and that would reduce the bending moment, possibly down to a safe level. Or, you may want to put a 29er mountain bike on there at some point, and want to protect for that eventuality.

Jeff