Upright vs. Forkmount

[jholmes]

Are there any stability issues I should be concerned with regarding either upright or fork mount bike racks? Is one type easier/ safer?

[captain crunch]

Okay, here's the skinny, fork mount racks like Thule's 590 V2, Yakima's SprocketRocket, or Rocky Mounts Lariat are a little easier to get your bike into, because your front wheel is off and you can hold onto your front fork, but then you have to put your front wheel somewhere. Try a wheel carrier.
Upright racks Thule's 594 Side arm or Yakima's Highroller are are nice if you have a DH bike with a thru axle, so you can leave the front wheel on. Uprights can be a bit tricky to load if you have a really high roof and you are vertically challenged like my friend Dave. As far as stabilty is concerned both are very stable, but I am partial to my Viper.