We have a 2017 ACE 30.1 and have experienced handling problems, particularly wind sensitivity and getting pushed around by passing trucks. We have made the following upgrades.
Each of them has has incremental improvement, with the net result being that the ACE is a lot easier to drive now. We had some very scary moments last fall on the I-70 going through the LeBec canyon east of Grand Junction. 45+ MPH swirling winds that made the ACE want to head for bad places off the road. At times we were down to 30 MPH. I think we'd have a much safer trip through there now.
Front End Alignment - We had this done by the local Ford Truck shop. We had to pay for it ($150), but some manage to persuade Ford to do it under warranty. You'll find lots of posts about how Thor doesn't fix alignment after piling on several tons of RV onto the factory aligned frame
Cheap Handling Fix (CHF) - First thing to do to reduce sway. This involves stiffening of the sway bars by moving the frame connection from the front holes to the back holes. Thousands of posts on the IRV2 forums -
Cheap Handling Fix - iRV2 Forums
Safe-T-Plus Steering Stabilizer - This keeps the steering wheel center and prevents a blow out from dragging you off the road
Koni FSD Shocks - Replaced the OEM Bilsteins with the Koni FSD shocks. Dramatic improvement in stability going over road bumps and dips. Also tends to help with sway
SuperSteer Trac Bar - Holds the rear frame in line with the rear wheels and eliminates tail wag. I think this is a must for the ACE 30.1 with the water tanks located behind the rear wheels. Dramatic improvement in the wind and we no longer get the push from a passing truck as it gets next to you followed by the suck when it goes past.
We are still thinking of adding SumoSprings, but likely will be next year if at all. You can get all of the above done for the cost of a set of Sumos. I'd make the above modifications and then decide if you need the Sumo's too.
Thor Forums
