For your 2014 Thor Siesta Motorhome built on a Mercedes Sprinter 3500 chassis, I recommend the SumoSprings Solo Custom Helper Springs item # SSR-338-54. These helper springs have a 1,400 lbs capacity that will help lift up the back end of your motorhome while not giving you a rough bouncy feeling.
The SumoSprings Maxim Custom Helper Springs item # SSR-106-47-1 you were looking at are for a 2104 Thor Siesta built on a Ford E-350 Chassis. view full answer...