the bikes and rack are both made to do this so I wouldn't worry about it. for context my parents are retired and drive all over the country with the same rack and two nice bikes. they run an extra cable lock through the wheels and frames along with the locks to attach it to their vehicle and enjoy their time exploring new places to ride. is the alternative to rent or not take them? that doesn't seem fun since you have all of the tools for a great trip - enjoy it.
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-zlin
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