The load range C ST175-80-13 tires you have on your trailer currently should have a capacity of 1,360 lbs.
To reduce your overall tire diameter about an inch without reducing your weight capacity you would want to go with a rim and tire combo with a 145/80-12 tire that is Load Range E like part # AM31215. This actually has more capacity at 1,520 lbs when inflated to 80 psi.
The bolt pattern of the rim of this combo is 5 on 4-1/2 inches. To determine your bolt pattern check out the link... view full answer...
The Volvo roof rack components are mostly rebranded Thule components. So for a Volvo roof rack key of N127 the correct replacement key is the part # THKEYN127. view full answer...
The rattle that you are experiencing is because the ball mount shank is slightly smaller than the receiver opening so that you can get it in and out easily. This is the same for any trailer hitch. The receiver depth has less, if any, impact on the rattle. but not to worry because I have a solution for you to take care of that annoying rattle.
The issue though with Class I trailer hitches is that most of the ball mounts for them are solid so an anti-rattle device like # SHP2082 would not... view full answer...