Will I be able to simply swap out my Claris rear derailleur with an Ultegra rear derailleur without any hassle? They both would have “long” cages. Bike is a stock Jamis Renegade
Shimano Claris 8-Speed Rear Derailleur - Berkshire Bike & Board | Great Barrington & Pittsfield
Amazon.com : Shimano Unisex's FDR2030F Bike Parts, Standard, One : Sports & Outdoors