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If you insist on a 2" class-3 hitch (to be able to carry four bicycles), then either the option is not provided by the car dealer, or the option that's provided is so lavishly priced that you decide to do it at a shop outside, which anyway specializes in attaching racks and hitches.

The independent shop will not weld the hitch assembly. It will fit using merely two bolts. (This sounds too good to be true, but anyhow.)

The only catch is that the bolts have a slightly larger diameter than the holes in the car's chassis, requiring enlarging the holes before attaching the assembly.

What rust precautions should one use when enlarging two holes in the chassis of a car?

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    What's the reason for the class 3 hitch? Seems overkill for some bikes.
    – barbecue
    Oct 21, 2023 at 2:19
  • @barbecue My current understanding is that a 4-bike hitch rack requires a class-3, 2" hitch. A class-1, 1-1/4" hitch will not take a 4-bike rack. The weight of four MTBs could reach 120 lbs, and the weight of a 4-bike rack is perhaps up to 80 lbs. A class-1 hitch rack is rated at 200 lbs, and so it could handle the load, but would offer no margin of safety. But in any case, 4-bike racks are made only with 2" hitches. Do correct me.
    – Sam7919
    Oct 21, 2023 at 3:23
  • I'm sure you're right, I know nothing of bike racks. A class-2 hitch would handle 300 lbs, which I would assume was plenty, but apparently bike people REALLY care about their bikes.
    – barbecue
    Oct 21, 2023 at 6:31
  • People who really care about their bikes, @barbecue, put them on the roof where other people who don't care about them can't ding them. I know some people forget the bike is up there and pull into the garage, but if I do that, at least it's my fault and not the fault of the person in the parking lot who let his shopping cart ram into my $3000 carbon frame...
    – FreeMan
    Oct 21, 2023 at 14:11
  • @FreeMan Joking aside, a roof rack is wonderful, but it's not the right solution if: 1- your car is too high (SUV, etc), 2- your bike is an MTB or, basp, a fatbike, or 3- you have studded tires and you'd really rather not scratch your car's finish.
    – Sam7919
    Oct 21, 2023 at 14:45

1 Answer 1

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Zinc spray ought to be enough. Alternatively rust converter.

The most important thing is the preparation: a nice clean degreased hole (Brake cleaner and compressed air)

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