I just recently purchased a Thule Parkway 956 Bike rack for a 2" hitch. When it was time to mount it, the spare tire got in the way. Furthermore, it looks as if it was mounted using a hitch extender the tailgate would not open completely. Well my question really is if Thule doesn't replace or reimburse me for the rack, I am considering purchasing the hitch extender. According to some, the hitch extender cuts the tongue weight capacity by 50%, making it 175 lbs capacity. Would it be safe to load it with 4 adult size mountain bikes? Thanks in advance.
That depends on the length of the hitch extender. The reduction of the capacity is a function of leverage, so a longer extender has a greater reduction of capacity because it gives the tongue of the trailer or the weight of the bikes and bikerack more leverage on the hitch.
I use a 18" hitch extender for my Thule T2 in order to clear the spare tire on my LJ on a regular basis. I usually use the hitch extender with 2 bikes, but I recently borrowed my brother's rack extensions which converts a 2-position Thule T2 into a 4-postion rack, and the weight wasn't a problem for the extender.
I used to use a 36" hitch extender on the back of the RV for a Sea-Doo trailer, and that package had the warning about a 50% reduction of tongue weight capacity. But an 18" extension wouldn't be as much of a reduction.
I did, however, decide against using the extender with the 4-position bike rack for longer trips (2,000+ miles) because the combination of the extender & the 4-position bike rack made for a very long overhang on the back of the Jeep. But the weight wasn't an issue.
If you need any proof of this, put a 10' section of 2" steel pipe into your hitch receiver sometime, and see how much you can lift up or push down on the back of your tow vehicle with simply your body weight. Then you're understand how much of a difference leverage makes.