You really don't want to use this kind of adapter, if that's what you are thinking of. These move the rack hitch quite a ways from the hitch, seriously increasing the force on the hitch itself and your car's suspension.
The 1Up racks, where the 1-1/4" to 2" adapter makes the normal rack part wider -- without moving the rack out -- is a much better choice.
no. the Golf/GTI is limited to a class 1 hitch.
BUT they make 1.25 > 2" adapters. super common.
you WOULD NOT want to do this if you were actually towing. you dont want to exceed the class I hitch ratings. but since this is just for a bike rack you'r well safe of that fact. just know, if you ever actually tow something, use the class I 1.25" hitch
Another thing to consider is to make sure to match the coupler with the hitch ball but NOT BY USING A HITCH ADAPTER!!! Most hitch adapter drops the maximum safe tongue weight significantly, usually by half. Your hitch is probably a class I or II receiver hitch. The ball mount size will be limited for those two and will probably be a 1 7/8" ball. Your trailer, given the size, probably has a coupler for 2" or 2 5/16" ball. What I'm saying is, do not use an adapter like this to use a larger shank and ball. Instead, swap out the coupler to fit the smaller ball.
I use the above adapter for my CT200h but only to attach a cargo basket and I'm extra mindful of the reduced weight capacity.
I think your best bet is to swap out the whole hitch receiver bar for one of these that is a standard hitch receiver.
https://www.etrailer.com/Trailer-Hitch/Geo/Tracker/Draw-Tite/24622.html
Most bike racks should fit the 1-1/4". If you need 2" you can then use an adapter like this:
https://www.amazon.com/MaxxHaul-70032-inches-Hitch-Adaptor/dp/B008CE09N4
It is possible to make an adapter for what you have, of course, but you're gonna pay someone to make it custom and then you're still going to have quite a bit of slop. If you switch to the other style I believe you'll be happier with the result (and it may be the same price anyway).
Im thinking to set something up like this as I have the same problem with a 1 1/14in hitch receiver.
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1 1/4in to 2in hitch adapter. Tongue capacity 350lbs
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Motorcycle hitch carrier
Or you could buy one that isnt a riser like this: http://www.amazon.com/gp/product/B008CE09N4?psc=1&redirect=true&ref_=oh_aui_detailpage_o05_s00