You now have a bike to car lock.
How to lock a bike to a car bike rack.
The insulation is totally optional it just depends on how worried you are about scratches.
Many bike racks include a locking mechanism but an additional lock is always a good idea.
A hitch rack provides a good lever that can be effectively used to snap the rack or the hitch off to take the bikes and if the bikes are damaged in the process the thief just walks away leaving a mess.
Remove anything that is removable from your bike.
Attach a u lock or chain around the rear wheel the frame and the bike rack as above.
While you can be sure the bikes are safely attached to the rack thieves are equally as sure that bike racks can be removed too.
Strong cable lock though a closed loop on the car the cars tie down loop eye around the bikes threaded to limit the range of twisting and lever motions meaning the racks locking mechanisms cannot be push further than they can cope with.
Whenever possible be sure to leave your car and bike in a well lit and populated area.
From here just thread the padded chain through the trunk loop the bike carrier and your bike and padlock the ends of the chain together.
This should help protect your bike your car and your carrier.
So make sure your carrier is also secured to your vehicle.
Lock your bike rack to your car.
Then push one end of the cable through the front wheel pass one loop through the other loop and secure the first loop to the main lock.
Google your vehicle make and model and add the words tow hooks or tow points for ideas or talk to a qualified auto mechanic dealer.
The several lock systems that i mentioned you should get are not just for your bikes but for your bike racks too.
Not only does it make thieft more difficult but it a visual deterrent to bike thieves in the first place.