I don't think there is any disadvantage to using a motorcycle GPS in a car. If you use a car GPS on a bike, the disadvantage could be missing features. For example, the Garmin Zumo models and the nuvi 500 and nuvi 550 (which are listed as "motorcycle friendly" by Garmin), all have a Track-back feature which allows you to find your way back to where you started your route. This is a very important feature to GS riders who are on trails or roads that are not on the map. I have never seen this feature on a car GPS.
Originally Posted by kantuckid