You carry one spare to use on either, instead of one spare for the trailer and one spare for the vehicle.
Hence the term 'extra spare'.
Some people paint their trailer to match their car, I suppose that is also unacceptable to you.
Here is a teardrop with whitewalls, it should make you even happier. It probably is pulled by a 75 year old classic car in mint condition.
Imagine the old guy, about your parents age, banging his wife inside, while you post on /out/.