Even if it is a spacer lift, it seems that lot of thought and development went into that setup in order to accommodate the bigger tires and maintain payload/towing capabilities, though I don't know who wants to tow heavy with 37's or 40's. They're very good products, regardless.
Carli and Thuren seem to take a completely different approach. I do wonder what, if anything, those kits do to address the out-of-stock angles created by their suspensions.
Understand that a stock Ram 4th gen Radius Arm truck will fit 37s stock with rims with ~20mm backspacing with minor rubbing so zero lift was needed for the tires.
Check out their websites. Carli uses drop brackets for the track bars just like AEV. Thuren uses less lift to avoid the need for adjustments. Thuren has a few articles on his website explaining how it all works and his alignment method, etc. Check the Tech tab.
Also, something that few people realize is that the springs on the later 4th gen Rams are extremely sensitive to coil design and how those coils fit in the buckets at a specific suspension height. AEV realizes this and uses the brackets to fix this on their spacer kit. Carli and Thuren also realize this and use a different configuration of the coil ends to address it. This is why simple spacer lifts on these trucks almost always result in bowed coils.
The ride improvement on an AEV lifted truck is SOLELY due to using 37" tires on 17" rims with significantly lower tire pressures from stock.
On Carli and Thuren lifts, the softer springs add a whole additional layer of better ride. On my truck, going from a stock 3500 SRW with 20s to 36" tires on 18s with Thuren springs I can definitely tell what difference the tires had and what difference the springs/Fox 2.0s had because I drove around for a week with just the wheel tire setup on the stock suspension. The Thuren Coils/Fox 2.0 combo significantly improved my ride. An AEV truck is going to ride very much like a stock truck with 37s on 17s because it uses stock springs. For reference, I ran my stock tires at 60F/45R. I ran my old Toyo AT 295/65R20s at 50F/40R. I run my current 315/70r18s at 45F/35R.
My stock truck rode horribly at stock pressures. My current setup rides like a lot of half tons.
